Detection and Treatment of Mineral Nutrition Problems in Grazing Sheep

E.ditors: D.G. Masters and e.l. White

Australian Centre for International Agricultural Research Canberra 1996 The Australian Centre for International Agricultural Research was established in June 1982 by an Act of the Australian Parliament. Its mandate is to help identify agricultural problems in developing countries and to commission collaborative research between Australian and developing country researchers in fields where Australia has a special research competence.

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© Australian Centre for International Agricultural Research GPO Box 1571, Canberra ACT 2601, Australia.

Masters, D.G., and White, c.L., ed. 1996. Detection and treatment of mineral nutrition problems in grazing sheep. ACIAR Monograph No. 37, iv + 117p.

ISBN 1 86320 172 6

Editorial management: Janet Lawrence Pre-press production: Arawang Information Bureau Pty Ltd Printed by: Watson Ferguson [, Co., Brisbane. Australia Contents

page

Foreword iv

Mineral deficiency problems in grazing sheep-an overview 1 David G. Masters

Understanding the mineral requirements of sheep 15 Colin L. White

Non-dietary influences on the mineral requirements of sheep 31 Neville F. Suttle

Diagnosis of mineral deficiencies 45 David I. Paynter

Trace element supplements for sheep at pasture 57 Geoffrey J. Judson

Free-choice mineral supplements for grazing sheep in 81 developing countries Lee R. McDowell

Toxicities and excessive intakes of minerals 95 John McC. Howell

iii Foreword

This book comprises selected papers presented at a workshop on mineral disorders in grazing sheep, which was held in Beijing in October 1995 as part of two research projects on mineral nutrition of sheep in China that have taken place over the last six years. The projects and workshop were funded by the Australian Centre for International Agricultural Research (ACIAR) and the Chinese Ministry of Agriculture.

Contributors were chosen for their sound practical knowledge of mineral deficiencies and toxicities in grazing sheep. Their contributions have produced a reference book designed to provide students, animal scientists, veterinarians, farmers and laboratory analysts with up-to-date, practical information on the detection and treatment of mineral disorders in grazing sheep. The emphasis is on extensive grazing systems, where treatment of mineral disorders may present special problems.

The projects involved scientists from the CSIRO Division of Animal Produc­ tion in Perth, Western Australia, the Beijing Institute of Animal Science, the Inner Mongolia and Xinjiang Academies of Animal Science, the Lanzhou Institute of Traditional Chinese Veterinary Medicine, the Chifeng Institute of Animal and Veterinary Science and the AusAID-IDP China-Australia Research Project. Results of the projects plus a number of allied developing country studies are presented in a companion volume produced in ACIAR's Proceedings Series.

John W. Copland R~search Program Coordinator, Animal Sciences ACIAR

iv Mineral Deficiency Problems in Grazing Sheep: an Overview

David G. Masters

CSIRO Division of Animal Production Private Bag. P.O Wembley. Western Australia 6014 Australia

Outline

Essential minerals Naturally occurring mineral deficiencies in grazing sheep Factors contributing to mineral deficiencies Content of minerals in pasture and feed supplements Soil type and conditions Time of the year and stage of maturity of the plant Use of fertilizer Pasture species Supplementary feeds Recent rainfall and climatic events Location Soil and faecal ingestion Efficiency of pasture use Economics of mineral supplementation References DETECTION AND TREATMENT OF MINERAL NUTRITION PROBLEMS IN GRAZING SHEEP

inerals are essential for life, to fulfil the tions using purified diets. For such ele­ Mneeds of growth and production and to ments, deficiencies in the field are unlikely. replace quantities lost during the course of In addition, some minerals listed in Table normal metabolism. Minerals participate in 1 are significant because they interfere with a range of biochemical reactions as compo­ the use of other nutrients and not because nents of enzymes and fulfil a structural and they are deficient in herbage or feed stuffs. osmotic role in a number of animal tissues. For example, high intakes of potassium decrease the absorption of magnesium and Essential Minerals may increase the incidence of grass tetany induced by magnesium deficiency At present 19 of the naturally occurring (May land and Grunes 1979). Similarly, high mineral elements are known to be essential. levels of molybdenum and iron reduce the A number of other minerals may be essen­ availability of dietary copper and may tial but the evidence is currently inconclu­ induce a deficiency in that element (Dick sive (Table 1). 1953; Suttle et al. 1984; Grace and Lee Deficiencies of many, but not all, essen­ 1990). Deficiencies of potassium, iron or tial minerals have been reported in grazing molybdenum have not been reported in ruminants. However, for some of the miner­ grazing sheep. als, requirements are extremely low relative Some elements are also of practical sig­ to the concentrations of these minerals nificance because of their toxicity, or accu­ found in natural feedstuffs, and animal mulation in animal tissues to concentrations responses have been demonstrated only in unacceptable for human consumption. the animal house under controlled condi- These include fluorine, mercury, cadmium

Table I. The essential mineral elements for animals.

Major elements (or macrominerals) Trace elements (or microminerals)

Calciuma Cobalta Nickel Chlorine Coppera Arsenic Phosphorusa Irona Vanadiumb Magnesiuma lodinea Boronb Potassiuma Manganese lithiumb Sodiuma Seleniuma Lead b Sulfura Zinca. Fluorineb Molybdenuma Cadmiumb Chromium Tinb Silicon a Important under grazing conditions. b Inconclusive evidence on essentiality.

2 MINERAL DEFICIENCY PROBLEMS IN GRAZING SHEEP: AN OVERVIEW - D. G. MASTERS

and aluminium, in addition to some of the example, in a series of experiments carried elements listed in Table 1 (see Howell, this out in Australia over a 4-year period, Lang­ pUblication). lands and colleagues (Langlands et al. 1991a,b,c) reported increased fleece Naturally Occurring Mineral weights (3.8-7.5%), fibre diameter (2- Deficiencies in Grazing Sheep 2.5%), lamb survival (up to 12%), lamb birth weight (4%), weaning weight (10.7%) and Mineral deficiencies occur in all continents wool production from lambs (8.6%) in and cause decreased production of meat, response to selenium supplementation. wool, milk and lambs. In many areas, During this 4-year period only two lambs rearing sheep and cattle was impossible exhibited overt signs of white muscle because a lack of minerals resulted in high disease. The responses described are not mortality or a complete failure to grow and specific for selenium-deficient sheep and are reproduce. These events often occurred likely to go undetected except through even when pasture was plentiful (see Under­ experiments using untreated controls for wood 1981; Grace 1983; McDowell et at. comparison or by extremely perceptive 1993). animal managers. An additional complica­ Mineral deficiencies may cause clinical tion is that responses are not necessarily disorders (Lewis and Anderson 1983) that consistent from year to year. LangJands et have dramatic effects on health and survival al. (1 991 b) observed increases in wool pro­ of sheep, or marginal deficiencies that result duction from selenium supplements in three in subtle and often undetected effects on years out of four. Lee ( 1 951) reported productivity (Table 2). While severe defi­ responses to cobalt in 8 of 13 years of ciencies still occur, they are becoming less experiments. Marginal deficiencies present frequent due to improvements in identifica­ the animal producers with the difficult tion and treatment. For example, copper problem of assessing mineral status in the deficiency, resulting in swayback in sheep and of evaluating the economic ben­ newborn lambs, was observed in New efits relative to costs of supplementation. Zealand, Australia, Europe and the USA in the 1930s (see Underwood 1981) but use of Factors Contributing to Mineral copper-containing fertilizers and routine Deficiencies treatment of sheep born in copper-deficient areas has decreased the incidence of severe Deficiencies are more likely to occur in deficiency. Similarly, supplements of iodine, grazing sheep dependent on locally grown cobalt and selenium are often provided rou­ pasture and feed supplements for all feed tinely in areas where there is a history of requirements. Under such conditions, both clinical deficiency. pastures and supplements are grown locally Marginal or subclinical deficiencies are and where mineral deficiencies or imbal­ not so readily identified and frequently ances exist in the soils, these are likely to be cause significant losses in production. For expressed in the grazing sheep.

3 DETECTION AND TREATMENT OF MINERAL NUTRITION PROBLEMS IN GRAZING SHEEP

Table 2. Summary of function and signs of severe and marginal mineral deficiencies and likely incidence of deficiencies.

Element Function Manifestation of deficiency Likely occurrence of deficiency

Severe Marginala

Calcium Mineralisation of bones and teeth. Lameness and stiffness of gait. Reduced growth. High grain diet especially during Nerve conduction. Enlarged painful joints. Reduced milk production. drought. Muscle contraction. Malformed teeth and jaws. Increased requirements in lactation. Blood dotting. Milk fever, including muscle Low calcium. acid soils in the Hormone secretion. tremors. general inertia, tropics. Message transmission. inappetance and death.b Low vitamin D.

Phosphorus Bone formation. Softening of bones. lameness. Reduced growth. Low soil phosphorus. Energy metabolism. Depressed appetite. Reduced reproductive Prolonged dry period with dead Component of DNA. RNA. Abnormal appetite causing rates. pasture. Acid-base balance. botulism.

Sodium Maintenance of osmotic pressure. Abnormal appetite. licking Abnormal appetite (pica). Tropical or dry arid climates. Acid-base balance. of soil. Reduced growth. Rapidly growing or lactating sheep. Water metabolism. Depressed appetite. Decreased milk High grain diets. Rumen microbial growth. Loss of weight. production. Decreased milk production.

Sulfur Component of amino acids Reduced feed intake. Reduced feed intake. Low sulfur soils. methionine and cysteine. Reduced dry matter Reduced wool growth. Dry pastures. Component of biotin and digestibility. thiamine. Reduced production of Sulfated polysaccharides in sulfur amino acids by rumen cartilage and joint lubrication. microbes. Removal and/or storage of toxic Possible accumulation of elements and compounds. copper in animal tissues and copper toxicity.

Cobalt Essential for the production of Loss of appetite. Reduced growthl Occurs under range of soils and vitamin B 12 by rumen microbes. Loss of weight. reduced unthriftiness. climatic conditions. Use of volatile fatty acids for wool growth. Reduced wool production. Sandy or volcanic soils. energy (as vitamin B 12)' Watery discharge from eyes. Green lush pasture. Recycling of methionine (as Anaemia. Young growing or reproducing vitamin B 12)' Popr reproductive sheep. performance. White (fatty) liver disease.

Continued on next page.

4 MINERAL DEFICIENCY PROBLEMS IN GRAZING SHEEP: AN OVERVIEW - D. O. MASTERS

Table 2. Confd.

Element Function Manifestation of deficiency likely occurrence of deficiency

Severe Marginala

Magnesium Cofactor in many enzymes. Tetany as indicated by Possible loss of condition. Green pasture. Nerve conduction. muscle twitching, staggers Possible reduced milk Often but not always associated Muscle contraction. and convulsions. production. with lactation. High mortality. High potassium, low sodium. Depressed appetite.

Copper Mobilisation and transport of Enzootic ataxia (swayback) as Leached low copper soils. iron in the body. paralysis or staggering gait in Peat soils high in molybdenum. Collagen cross-linking in bone newborn lambs. Use of molybdenum fertilizer. and elastic tissue. Bone fragility. Pigmentation of hair and wool. Anaemia. Maintenance of myelin sheath Depigmentation of wool. around nervous tissue. Loss of crimp and tensile Crimp formation in wool. strength of wool. Antioxidant. Reproductive disorders.

Iodine Component of thyroid hormones Enlarged thyroid gland (goitre) Increased lamb mortality Low soil iodine. that are essential for energy and Inability to withstand cold and thyroid size relative Recent glaciation. protein metabolism and for foetal stress. to body size. Mountainous areas. growth and development. Reduced foetal size and Small depression in wool Long distance from the sea. retarded brain development. and milk production. Low rainfall. A range of developmental Goitrogens in herbage. disorders, wool loss.

Selenium Detoxification of peroxides. Lesions in heart and skeletal Reduced growth/illthrift. Green pasture. Activation of thyroid hormone. muscle (nutritional myopathy Reduced wool growth. Low selenium in soil. or white muscle disease). High rainfall. Increased mortality. Young growing or reproducing Infertility in ewes. sheep. Induced thyroid hormone Low vitamin E. deficiency.

Zinc Cofactor in a large number of Reduced feed intake. Reduced growth rate. Low zinc soils. enzymes. Reduced gro.wth rates. Reduced reproductive Dry pasture. DNA and protein synthesis. Reduced wool growth and performance. loss of crimp. Alopecia, parakeratosis. a Marginal signs may also be seen during severe deficiency. b Acute deficiency resulting from a rapid loss of calcium during milk letdown.

5 DETECTION AND TREATMENT OF MINERAL NUTRITION PROBLEMS IN GRAZING SHEEP

Content of minerals in pasture and feed of organic material; drainage and waterlog­ supplements ging; and the proliferation of plant roots within the soil. These have been reviewed by Deficiencies of minerals usually occur Hannam and Reuter (1987). Use of soil within specific geographical regions. Soil mapping techniques to define areas of types and climatic conditions will determine mineral deficiency in grazing animals have the types and amounts of minerals available met with limited success due to the many for absorption by the pasture plants and interacting factors affecting availability and other local plant species. However, there are use of minerals (Lewis 1985). many secondary factors that will contribute to the expression of potential mineral prob­ Time of the year and stage of maturity lems. These include: time of the year (stage of the plant. The effects of time of the year of plant growth); amounts and types of ferti­ and stage of plant maturity on mineral con­ lizer used; introduction of improved pasture centrations in plants are interrelated. Con­ species; short term climatic factors (recent centrations of phosphorus, sodium, rainfall and temperature); distance from the potassium, sulfur, iodine and zinc fall as the ocean; and amounts and types of supple­ plant matures (Purser and Southey 1984; mentary feeding. These factors influence the Minson 1990; Hendricksen et al. 1992). No supply of minerals to grazing sheep. Animal consistent changes have been reported for factors that influence requirements are calcium and magnesium, with some indica­ equally important (White, this publication). tions that concentrations either decrease or remain the same (Mayland and Grunes Soil type and conditions. The availabil­ 1979). Consistent trends have not been ity of minerals to plants depends on the reported for copper, selenium and cobalt. concentration and the chemical form of In environments with extreme changes in these elements in the soil (Thornton 1983). season, pasture available for grazing may The soils will initially resemble the parent be dead and dry for extended periods of the rock in composition. But with older soils, year. These environments include the medi­ elements may have been mobilised and terranean climate, as found in much of redistributed through the soil profile and/or southern Australia, where low rainfall and into neighbouring soil zones. Prolonged high temperatures exist for 4-6 months leaching of soils in high rainfall areas will each year (Purser 1980). and the cold tem­ increase the rate of mineral loss and reqis­ perate environments, such as found in the tribution. The process of soil formatioQ pastoral regions of northern China. where varies with climate and this will also influ­ low rainfall and extreme cold exist for 4-6 ence the concentration and form of miner­ months each year (Masters et a!. 1990). als in the soil. These conditions may cause marked fluctu­ Other factors influencing availability of ations in the amount and availability of min­ minerals from soils include: the nature of the erals to grazing sheep. soil solution (particularly pH); the amount Table 3 shows the changes in mineral

6 MINERAL DEFICIENCY PROBLEMS IN GRAZING SHEEP: AN OVERVIEW - D. G. MASTERS

concentrations in mixed pastures as they tures and so requirements for minerals may change from the green to the dry stage. be reduced or deficiencies masked (White, Most elements show a decrease in concen­ this publication). The increased concentra­ tration-selenium and iron are exceptions. tion of iron in dry pastures results (at least in Sheep grazing dry pastures may not part) from soil contamination. High intakes consume sufficient minerals to meet the of iron may depress growth of young sheep published requirements for a significant (Wang 1995) or interfere with the utilisation period during each year, and deficiencies of copper. may result. Deficiencies in phosphorus in The green pasture phase is also asso­ grazing cattle in South Africa have been ciated with mineral problems. The concen­ associated with low soil phosphorus trations of cobalt and selenium tend to be at together with a prolonged dry period their lowest during rapid pasture growth. (Underwood 1981). However, the low con­ Because plants do not require selenium for centrations of minerals in dry pastures do growth and the requirement for cobalt by not necessarily mean that signs of defi­ the plant is less than that required by the ciency will result. The content of digestible ruminant, plants can display vigorous energy and protein is also low in dry pas- growth when little selenium or cobalt is

Table 3. Concentration of minerals in pasture during the green or dry phases in Western Australia and north-west China (mg/kg dry matter).

Element Western Australiaa North-west Chinac

Green Dry % Change Green Dry % Change

Calcium 8300 8715 +5 6500 4400 -32 Phosphorus 3800 1444 --62 1546 240 -85 Magnesium 1750 1380 -21 Potassium 28100 6182 -88 14900 2252 -85 Sodium 92 210 +130 Sulfur 3240 1458 -55 1900 830 -56 Copper 7.3 6.9 -6 6.8 4.4 -35 Iron 128 141 +10 903 2091 +57 Manganese 74 20 -73b 67 67 0 Selenium 0.025 0.05 +IOOb 0.03 0.06 +100 Zinc 43.3 18.6 -57 25.6 9.6 -63 Molybdenum 3.4 2.4 -30 2.1 2.1 0 a Purser and Southey (1984). b Masters and White (1986).

C Masters et al. (1993a.b) and Masters et al. (unpubl.).

7 DETECTION AND TREATMENT OF MINERAL NUTRITION PROBLEMS IN GRAZING SHEEP available. Consequently during rapid whereas the availability of most of the pasture growth the available cobalt and cations including copper, zinc, cobalt, iron selenium are diluted within the plant and the and manganese decreases (Williams 1977; concentration of these elements is reduced Hannam and Reuter 1987). (Hunter et al. 1982; Clark and Millar 1983) Interactions between elements in the soil and deficiencies result (Hosking et al. also influence the response to fertilizers. 1986). In general, any factor that increases Application of potassium fertilizer markedly plant growth without changing the amount reduces the concentration of sodium, or availability of minerals in soil will result in calcium and magnesium in plants. This depressed mineral concentrations in plants. leads to lower serum magnesium in sheep Therefore, more widespread deficiencies and increases their susceptibility to grass may be expected as crop and pasture pro­ tetany (Mayland and Grunes 1979; Minson ductivity increases. 1990). Overuse of molybdenum fertilizers to improve plant growth may result in reduced Use of fertilizer. The use of fertilizer may absorption of copper by the animal, and raise mineral levels directly by providing an copper deficiency (Langlands et al. 1981). available source to the plant. Such fertilizers Application of phosphate or nitrogen ferti­ have been used successfully to increase lizers to increase the rate of plant growth concentrations of calcium, phosphorus, may cause a dilution and reduced concen­ potassium, sulfur, magnesium, sodium, tration of copper (Reuter et al. 1981), sele­ copper, iodine, zinc, selenium and cobalt in nium and cobalt (Halpin et al. 1981) or may the plant. Simply because mineral fertilizers change mineral status of the grazing sheep increase the concentration of an element in through changes in the proportions of grass the plant does not necessarily mean that and legumes within a pasture. this is an economical method of supple­ mentation. High rates of application to the Pasture species. The type of pasture soil may be needed to provide modest species will influence mineral supply to increases in concentrations in the plant. grazing sheep. Temperate grasses and Judson and McDowell in this publication cereals generally contain less calcium, both advocate more direct methods of sup­ phosphorus, potassium, magnesium, iron, plementation under such circumstances. copper, zinc, molybdenum and cobalt but Fertilizer use may also indirectly affect more selenium than temperate legumes mineral content of plants by changing (Reid and Horvath 1980; Underwood 1981; factors such as soil pH, the availabiHty of Minson 1990), but these differences are not competing elements to the plant, the rate of consistent and the trends may be reversed pasture growth or pasture composition. in tropical pasture species. There are also Application of lime raises the pH of the soil plants termed 'accumulator' plants that and changes the solubility of several miner­ contain high concentrations of some ele­ als. The availability of molybdenum and ments. Plants considered as weeds may selenium increases as soil pH increases also contain Significantly different mineral

8 MINERAL DEFICIENCY PROBLEMS IN GRAZING SHEEP: AN OVERVIEW - D. G. MASTERS

concentrations compared with grass or nium, cobalt and sodium are either not legume species grown on the same site required for plant growth or only required in (Gladstones and Loneragan 1970). small amounts, and concentrations in plants Improvement of pastures that results in a decrease with increasing rates of plant change in the predominant pasture species, growth. Low mineral concentrations in together with applications of fertilizer, will plants and increased incidence of deficien­ change the mineral content of pastures and cies occur when seasonal conditions are may cause signs of deficiency in plants favourable for plant growth. For example, in and/or grazing animals. areas that support only annual species of pasture plants, selenium and cobalt defi­ Supplementary feeds. Supplementary ciencies are more likely when there is an feeds may be conserved fodder such as early start to the growing season, due to silage and hay, or grain and pulses. Silage early rainfall and other conditions that are and hay, if prepared on-farm, will have a favourable to plant growth. Rainfall may also mineral composition similar to the pasture. influence waterlogging of soil, and this may Grains and pulses, however, contain differ­ increase concentrations of cobalt, manga­ ent concentrations of minerals compared to nese and selenium in plants, although the vegetative stage of the plant and also responses are not always consistent. minerals in different relative proportions. The selection of supplement may exacer­ Location. Proximity to the ocean has a bate or alleviate potential deficiencies. For significant impact on minerals in plants, example, dry pasture and hay contain low particularly sodium and iodine. Both sodium concentrations of phosphorus and potas­ and iodine are carried on to pasture in sea sium while cereal grain and some grain spray or, in the case of iodine, through vola­ legume seeds contain higher concentra­ tilisation from sea water. Iodine deficiency is tions of phosphorus, both in absolute terms usually found in mountainous regions, often and relative to calcium and potassium. A with low rainfall and located a long distance deficiency in phosphorus on dry pastures is from the sea. Sodium deficiency is more therefore unlikely if cereal grains or grain common in tropical or inland semi-arid cli­ legume seeds are used as supplements mates. either instead of or with conserved fodder. In environments that have prolonged dry Soil and faecal ingestion periods and high levels of supplementary feeding with little pasture, calcium defi­ Ingestion of soil and faeces by grazing ciency may occur (Langlands et al. 1967) sheep will influence mineral status. Healy due to low calcium intake together with the (1967) reported that faeces from sheep high phosphorus in cereal grains. grazing in New Zealand contained up to 50% soil (corresponding to 0.4 kg/day of Recent rainfall and climatic events. ingested soil) when available feed for Recent rainfall may also be important. Sele- grazing was low. Estimates of the minerals

9 DETECTION AND TREATMENT OF MINERAL NUTRITION PROBLEMS IN GRAZING SHEEP available from the soil indicated that sub­ material ingested by the sheep was faeces. stantial amounts of calcium, magnesium, Faeces can contain a substantial amount of phosphorus, manganese, zinc, iron, copper, calcium, phosphorus, sodium, potassium, molybdenum, cobalt and selenium are iron and zinc (Masters et al. 1993a,b). There absorbed by the sheep. The amounts is little information on the availability of absorbed will depend on the type of soil. minerals from faeces. Ingestion of soils high in iron depresses copper status, probably through an antago­ Efficiency of Pasture Use nistic interaction between copper and the iron supplied in the soil (Suttle et al. 1984). A consistent sign of deficiency of many ele­ Vu et al. (1995) suggested that a lack of ments is a reduction in feed intake and in ,sodium in pasture caused increased soil the efficiency of digestion and utilisation of ingestion in grazing sheep in China. This in ingested nutrients (Table 2). The reduction turn resulted in increased intakes of the iron in intake will mean that a higher proportion in the soil and depressed copper status. of feed consumed will be used for mainte­ Langlands et al. (1982) reported only nance of liveweight and non-productive small changes in selenium status and no processes such as thermoregulation, loco­ changes in copper status when sheep were motion and excretion, and less will be avail­ given approximately 100 gjday of either able for Iiveweight gain. black clay or red sandy loam through a With depressed intake under grazing rumen fistula. conditions, stocking rate would need to Less information is available on rates of increase to utilise all available pasture. This consumption or availability of minerals would result in lower liveweight gain per from faeces. Peter et al. (1987) suggested, hectare (approximately 170 gjhajday in from visual observations on oesophageal the example shown, Table 4) with no samples collected when pasture availability change in total wool production. The diam­ was extremely low, that up to 50% of the eter of wool fibres would be reduced as a

Table 4. Changes in productivity when intake of each sheep is depressed by 17% and stocking rate is increased by 17% to utilise all the pasture.a

Sheep/ha Feed consumed/day Uveweight gain/day Wool growth/day Sheep costs/dayb

kg/head kg/ha g/head g/ha g/head g/ha $/head $/ha

5 1.43 7.15 197 9Bs B.7 43.5 3.00 15.00 6 1.19 7.14 136 BI6 7.2 43.2 3.00 IB.OO a Figures derived from GrazFeed (1993) computer program for 30 kg wether weaners, 12 months of age consuming green pasture. Pasture availability was adjusted within the program to derive intakes. b Costs in A$ derived from shearing. drenching. eartags. vaccines etc. (A. Herbert. Department of Agriculture. Western Australia, pers. comm.).

10 MINERAL DEFICIENCY PROBLEMS IN GRAZING SHEEP: AN OVERVIEW - D. G. MASTERS

consequence of lower production per (Morley et al. 1978) and subsequently lower sheep. This would increase the value of lambing percentages and increased mortal­ wool per kilogram (partially offsetting the ity or a higher requirement for supplemen­ reduction in liveweight gain) in Australia, tary feeds. where diameter is a major determinant of wool price, but not in countries such as Economics of Mineral China, where all wool of less than 25 Supplementation microns is considered fine wool (Longworth 1990). Because the amount of minerals required A rise in the number of sheep per hectare by sheep is generally small relative to increases the total costs for shearing, para­ requirements of protein and energy, the site control and other processes required cost of supplements is often low. This is for each individual animal. Therefore, particularly true for the trace elements that overall production per hectare decreases are required in milligram or microgram but costs increase. Higher stocking rates quantities each day. For example, Masters will also contribute to damage to grasslands et al. (1995) estimated that the actual cost and pastures through soil compaction, of copper and selenium, if supplied as trampling and erosion. copper sulfate and sodium selenate, is Lower efficiency of use of ingested nutri­ approximately 2.5 cents (Australian cur­ ents results from deficiencies or imbalances rency) per sheep each year. Use of these of a number of elements including sele­ elements to correct marginal deficiencies in nium, sodium, calcium/phosphorus (as a China, in the experiments described, had ratio), copper and zinc. This means that increased the value of production by 48 productivity may be decreased without a cents. There are extra costs associated with decrease in voluntary feed intake or that the incorporation of these elements into salt efficiency of use of nutrients may be or other supplements. In countries where decreased in addition to a reduction in salt supplements are used routinely, or intake (Underwood 1981). where sheep are tended continuously by Reduction in either intake or efficiency of herdsmen, these costs would be small. use of ingested nutrients will therefore result The potential return, even from correcting in reduced liveweight and/or wool growth marginal deficiencies, is then many times per unit of pasture available. In environ­ the cost of the supplements. Economic ments that experience prolonged periods of analysis of this earlier research in China (M. dry low quality grazing, any reduction in Fearn, unpublished data) has indicated that weight gains during periods of adequate or an increase in wool production of 7% abundant feed availability will mean that together with a 4% increase in weaning rate, sheep will be in poorer condition at the start achieved at a supplement cost of 19 cents of the dry period, have less body stores to per head each year, would result in a unit buffer against the decrease in nutrient avail­ cost reduction of 4.8% for wool and 0.1% for ability, have decreased ovulation rates meat.

I1 DETECTION AND TREATMENT OF MIf'IERAL NUTRITION PROBLEMS If'I GRAZIf'IG SHEEP

When minerals are supplied as commer­ Dick, A.T. 1953. The control of copper storage in cially prepared supplements marketed for the liver of sheep by inorganic sulphate and sheep, costs will increase substantially but molybdenum. Australian Veterinary Journal, 29, 233-239. returns may still be high relative to costs. Edwards, J.R. 1982. Selenium trials in the Edwards (1982) assessed the results of 14 Albany region. Proceedings of a workshop on selenium trials carried out in the high rainfall trace minerals in grazing livestock in Western areas of Western Australia. Average results Australia. Perth, Western Australian Depart­ over all the trials showed that selenium sup­ ment of Agriculture, 107-121. plementation increased body weight by Gladstones, J.S. and Loneragan, ...I.f. 1970. 3.9%, wool growth by 5% and decreased Nutrient elements in herbage plants in relation mortality by 1.8%. Even with these relatively to soil adaptation and animal nutrition. Pro­ ceedings of the XI International Grassland small responses, supplementing all sheep Congress. St. Lucia, University of Queensland with commercial selenium pellets would Press. 350-354. have provided a return of more than 300% Grace, N.D. 1983. The Mineral Requirements of on funds invested. Grazing Ruminants. Occasional Publication Macromineral supplements are usually No. 9, New Zealand Society of Animal Pro­ more expensive than the trace elements. duction. This is primarily because these elements are Grace, ND. and Lee, J. 1990. Effect of increas­ required in gram quantities each day. ing fe intake on the fe and Cu content of tissues in grazing sheep. Proceedings of the Masters et al. (1995) reported that in north­ New Zealand Society of Animal Production, ern China a I-year supplement of micro­ 50, 265-268. minerals costing 101 cents (Australian GrazFeed 1993. A nutritional management currency) resulted in a gross return of only system for grazing ruminants. Roseville, approximately 50 cents. Therefore the eco­ Horizon Technology Pty Ltd. nomics of correcting marginal deficiencies Halpin, c., Caple, I., Schroder, P. and McKenzie, may not warrant the use of multi-element R. 1981. Intensive grazing practices and sele­ supplements over prolonged periods. nium and vitamin B 12 nutrition of sheep. In: Where deficiencies exist, supplements need Howell, J. McC., Gawthorne, J.M. and White, c.L., ed., Trace Elements in Man and Animals: to be strategically used during the times of 4. Canberra, Australian Academy of Science, the year when sheep will respond. Where 222-225. severe deficiencies exist or where the spe­ Hannam, R. J. and Reuter, D.J. 1987. Trace cific deficiencies are identified, returns will element nutrition of pastures. In: Wheeler, be sufficient to justify treatment. J.L., Pearson, c.J. and Robards, G.E., ed., Temperate Pastures-Their Production, Use and Management. Melbourne, Australian Wool References CorporationjCSIRO, 175-190. Clark, R.G. and Millar, K.R. 1983. Cobalt. In: Healy, W.B. 1967. Ingestion of soil by sheep. Grace N.D., ed., The Mineral Requirements of Proceedings of the New Zealand Society of Grazing Ruminants. Occasional Publication Animal Production, 27, 109-120. No. 9, New Zealand Society of Animal Pro­ Hendricksen, R.E., Gilbert, M.A. and Punter, L.D. duction, 27 -37. 1992. Effect of superphosphate application on

12 MINERAL DEFICIENCY PROBLEMS IN GRAZING SHEEP: AN OVERVIEW - D. G. MASTERS

macro-nutrient and micro-nutrient concentra­ 1967. Observations on the calcium intake and tions in grazed stylo-native grass pasture in serum calcium status of grazing ewes during tropical Australia. Australian Journal of Agri­ drought. Australian Journal of Experimental cultural Research, 43, 1725-1738. Agriculture and Animal Husbandry, 7, 325- Hosking, W.J., Caple, l.W., Halpin, c.G., Brown, 328. A.J., Paynter, 0.1., Conley, D. N. and North­ Lee, H.J. 1951. Cobalt and copper deficiencies Coombes, P.L. 1986. Trace Elements for Pas­ affecting sheep in South Australia. Journal of tures and Animals in Victoria. Melbourne, Agriculture, South Australia, 54, 1-22. Department of Agriculture and Rural Affairs. Lewis, G. 1985. Identification of the high-risk Hunter, R.A., Peter, D.W., Quinn, M.P. and environment for deficiency and excess in Siebert, B.D. 1982. Intake of selenium and animals. In: Mills, C.F., Bremner, I. and Ches­ other nutrients in relation to selenium status ters, J.K., ed., Trace Elements in Man and and productivity of grazing sheep. Australian Animals-5. Slough, Commonwealth Agricul­ Journal of Agricultural Research, 33, 637- tural Bureaux, 913-917. 647. Lewis, G. and Anderson, P.H. 1983. The nature of Langlands, J.P., Bowles, J.E., Donald, G.E. and trace element problems: delineating the field Smith, A.J. 1982. The nutrition of ruminants problem. In: Suttle, N.F., Gunn, R.G., Alien, grazing native and improved pasture. V: W.M., Linklater, K.A. and Wiener, G., ed., Trace Effects of stocking rate and soil ingestion on Elements in Animal Production and Veterinary the copper and selenium status of grazing Practice. British Society of Animal Production, sheep. Australian Journal of Agricultural Occasional Publication No. 7, 1] -16. Research, 33, 313-320. Longworth, J.W. 1990. The Wool Industry in Langlands, J.P., Bowles, J.E., Donald, G.E., China. Mount Waverley, lnkata Press. Smith, A.J. and Paull, D.R. 1981. Copper McDowell, L.R., Conrad, J.H. and Hembry, F.G. status of sheep grazing pastures fertilized with 1993. Minerals for Grazing Ruminants in sulfur and molybdenum. Australian Journal of Tropical Regions, 2nd ed. Gainesville, Animal Agricultural Research, 32, 479-486. Science Department, University of Florida. Langlands, J.P., Donald, G.E., Bowles, J.E. and Masters, D.G., Purser, D.8., Vu, S.X., Wang, l.S., Smith, A.J. 1991 a. Subclinical selenium insuf­ Vang, R.l., Liu, N., Wang, X.L., Lu, D.X., Wu, ficiency. 1: Selenium status and the response L.H., Rang, W.H., Ren, J.K. and Li, G.H. 1990. in liveweight and wool production of grazing Production from fine wool sheep in three areas ewes supplemented with selenium. Australian in northern China. Asian-Australasian Journal Journal of Experimental Agriculture, 31, 25- of Animal Science, 3, 305-312. 3L Masters, D.G., Purser, D.B., Vu, S.X., Wang, l.S., -1991 b. Subclinical selenium insufficiency. 2: Vang, R.l., Liu, N., Lu, D.X., Wu, L.H., Ren, The response in reproductive performance of J.K. and Li, G.H. 1993a. Mineral nutrition of grazing ewes supplemented with selenium. grazing sheep in northern China. I: Macro­ Australian Journal of Experimental Agricul­ minerals in pasture, feed supplements and ture, 31, 33-35. sheep. Asian-Australasian Journal of Animal -1991 c. Subclinical selenium insufficiency. 3: Science, 6, 99-105. The selenium status and productivity of lambs -1993b. Mineral nutrition of grazing sheep in born to ewes supplemented with selenium. northern China. 11: Selenium, copper, molyb­ Australian Journal of Experimental Agricul­ denum, iron and zinc in pasture, feed supple­ ture, 31, 37-43. ments and sheep. Asian-Australasian Journal Langlands, "LP., George, J.M. and Lynch, J.J. of Animal Science, 6, 107 - 113.

13 DETECTION AND TREATMENT OF MINERAL NUTRITION PROBLEMS IN GRAZING SHEEP

Masters, D.G. and White, C.L. 1986. The role of Reid, R. and Horvath, D.J. 1980. Soil chemistry trace elements during pregnancy and early and mineral problems in farm livestock: a growth of lambs. In: On-farm Management of review. Animal Feed Science and Technology, Ewes and Lambs during Autumn. Perth, Aus­ 5,95-167. tralian Society of Animal Production. Reuter, D.J., Robson, A.D., Loneragan, J.F. and Masters, D.G., Vu, S.X., Wang, l.S., Lu, D.X., Wu, Tranthim-rryer, D.J. 1981. Copper nutrition of L.H., Ren, J.K., Li, G.H. and Purser, D.B. 1995. subterranean clover (Trifolium subterran­ Consequences of mineral deficiencies in eum L. cv. Seaton Park). Ill: Effects of phos­ sheep in northern China. In: Anderson, N., phorus supply on the relationship between Peter, D.W., Masters, D.G. and Petch, D.A., copper concentrations in the plant parts and ed., Production of Fine Wool in Northern yield. Australian Journal of Agricultural China: Effect of Nutrition and Helminth Infec­ Research, 32, 283-294. tions. Canberra, Australian Centre for Interna­ Suttle, N.F., Abrahams, P. and Thornton, I. 1984. tional Agricultural Research, Technical Report The role of a soil x sulfur interaction in the No. 32,45-50. impairment of copper absorption by ingested Mayland, H.F. and Grunes, D.L. 1979. Soil­ soil in sheep. Journal of Agricultural Science, climate-plant relationships in the etiology of Cambridge, 103, 81-86. grass tetany. In: Rendig, V.V. and Grunes, D.L., Thornton, I. 1983. Soil-plant-animal interac­ ed., Grass Tetany. Madison, American Society tions in relation to the incidence of trace of Agronomy, 123-175. element disorders in grazing livestock. In: Minson, D.J. 1990. Forage in Ruminant Nutri­ Suttle, N.F., Gunn, R.G., Alien, W.M., Linklater, tion. San Diego, Academic Press. K.A. and Wiener, G., ed., Trace Elements in Morley, F.H.W., White, D.H., Kenney, P.A. and Animal Production and Veterinary Practice. Davis, I.F. 1978. Predicting ovulation rate British Society of Animal Production, Occa­ from liveweight in ewes. Agricultural Systems, sional Publication No. 7, 39-49. 3,27-45. Underwood, E.J. 198 L The Mineral Nutrition of Peter, D.W., Purser, D.B., Buscall, D.J., Hill, J.D., Livestock, 2nd edition. Slough, Common­ Southey, I.N. and Hunter, R.A. 1987. Esti­ wealth Agricultural Bureaux. mates of the apparent absorption and/or Wang, l.S. 1995. Adverse effect of high intakes digestibility of trace elements in g razing sheep of iron in sheep. PhD Thesis, UniverSity of in a mediterranean environment. In: Wheeler, Western Australia. J.L., Pearson, c.J. and Robards, G.E., ed., WilIiams, C.H. 1977. Trace metals and super­ Temperate Pastures-Their Production, Use phosphate: toxicity problems. Journal of the and Management. Melbourne, Australian Wool Australian Institute of Agricultural Science, 43, Corporation/CSIRO, 393-395. 99-109. Purser, D.B. 1980. Nutritional value of mediter­ Vu, S.X., Masters, D.G., Purser, D.B., Wang, l.S., ranean pastures. In: Morley, F.H.W., ed., Yang, R.l., Liu, N., Lu, D.X., Wu, L.H., Ren, Animals. Amsterdam, Elsevier Scien- . J.K. and Li, G.H. 1995. Description of the trace tific Publishing Company, 159-180. element status of sheep in three areas of Purser, D.B. and Southey, ioN. 1984. Fluctua­ northern China. In: Anderson, N., Peter, D.W., tions in nutrient supply in the south-west of Masters, D.G. and Petch, D.A., ed., Production Western Australia. In: Baker, S.K., Masters, of Fine Wool in Northern China: Effect of D.G. and Williams, I.H., ed., Wool production Nutrition and Helminth Infections. Canberra, in Western Australia. Perth, Australian SOciety Australian Centre for International Agricultural of Animal Production, 99-1 11. Research, Technical Report No. 32, 35-39.

14 Understanding the Mineral Requirements of Sheep

Colin L. White

CSIRO Division of Animal Production Private Bag. P.O Wembley, Western Australia 6014 Australia

Outline

What is meant by requirement? What factors affect requirements? Animal factors Genotypiclphenotypic differences Age, physiological state and sex of the animal Rate and type of production Dietary factors Determining the minimum requirement for a nutrient Published tables of requirements Estimating values of requirements Experiments using semi-purified diets Experiments using practical diets The factorial method Conclusions References

IS DETECTION AND TREATMENT OF MINERAL NUTRITION PROBLEMS IN GRAZING SHEEP

roducers and advisers need to know within healthy limits the concentrations and Pthe mineral requirements of sheep in active forms of the mineral in all tissues order to formulate diets and predict and including storage organs, and maintain the detect deficiencies. Published tables of rec­ levels of the mineral in the product, such as ommended mineral requirements for sheep, milk. such as those from the National Research Under practical farming conditions, Council in the USA (NRC 1985), the Agri­ where efficient production is the main aim, cultural Research Council in the U.K. (ARC it is not always necessary to maintain 1980) and the Standing Committee on storage levels because a reduction in this Agriculture in Australia (SCA 1990) are pool of minerals does not immediately useful in determining whether a particular affect production. Reduced productivity diet will meet an animal's requirements. comes at the end of a series of events after There are some problems, however, espe­ dietary depletion of a mineral (Fig. 1). cially when it comes to applying the values Levels within storage organs are the most to grazing animals. For example, many sensitive to changes in intake of the nutri­ published tables of requirements include a ent, followed by levels in transport forms safety margin, the extra amount of which, in and finally enzyme activity and metabolic most circumstances, does not lead to function. Once enzyme activity and meta­ increased production. In intensive produc­ bolic processes are impaired then produc­ tion systems it is a relatively inexpensive tion falls and clinical signs appear. In most task to add minerals above minimum cases storage levels must be almost com­ requirement levels as an insurance policy. pletely depleted before a measurable drop Under extensive grazing systems, however, in production occurs. It follows from this it is usually difficult and costly to provide that requirements are not a fixed value but supplementary minerals, and so it is impor­ vary with the criteria of adequacy adopted. tant to know whether the published tables of For example, dietary copper deficiency in requirements represent minimum values or sheep is characterised as a decline in liver whether they include generous over­ copper reserves from a normal range of allowances. between 1.6 and 4.7 mmol/kg dry matter This chapter summarises the various (DM), to below 0.3 mmol/kg DM. At this methods used to estimate the mineral point plasma copper concentration and requirements of sheep and highlights both plasma caeruloplasmin activity decline to the limitations and usefulness of SUCD about 20% of normal values. Within a methods for identifying and preventing defi- . month the first clinical signs appear, char­ ciencies in practical grazing situations. acterised as defects in wool. The time to appearance of clinical signs What Is Meant by Requirement? depends on the severity of the deficiency and the mineral in question. Some ele­ To meet all mineral requirements the ments, such as magnesium, are not stored minimum dietary supply must maintain to any extent in the body and need to be

16 UNDERSTANDING THE MmERAL REQUIREMENTS OF SHEEP - C. L. WHITE

supplied from the diet continually to What Factors Affect prevent deficiency. Other elements, such as Requirements? calcium and phosphorus, can be drawn from bone which offers a period of protec­ The dietary requirements for a mineral are tion against production losses, albeit at the influenced by both animal and dietary cost of fragile bones. Grazing sheep typi­ factors. cally face environments where mineral supply varies greatly between seasons, and Animal factors in these circumstances it i~ advantageous for the sheep to build up reserves in one Genotypic/phenotypic differences. Ani­ season for use in another. Thus, although mals of similar age, breed and physiological the diet may be technically deficient in state in a common environment can show minerals at certain times of the year, the marked differences in their efficiency of supply of minerals from body reserves such mineral utilisation. For example, the frac­ as liver and bone can provide sufficient tional absorption of copper can vary from quantities to meet requirements for the 0.042 to 0.112 (Suttle 1974). In grazing short period of dietary deficiency. sheep, Wiener and Field (1970) reported heritable differences among three breeds and their crosses in susceptibility to sway­ back and copper poisoning. Age, physiological state and sex of the animal. Age can affect requirement through changes in absorption efficiency. 1 2 Slorage Transport For example, preruminating lambs have an 100 80% absorption efficiency for copper, whereas lambs with a functional rumen have only 3-5% (Underwood 1981). Sex of the sheep affects mineral require­ C ments through differences in growth rates .91 3 and physiological functions. Rams grow z faster than ewes and so require a greater

5 daily supply of minerals; pregnant and lac­ Clinical signs tating ewes require more minerals to meet body demands than non-pregnant females at maintenance (ARC 1980, see Table 1). o Animals compensate for this by increasing Depletion Deficiency Dysfunction Disease absorption of most nutrients during late pregnancy and lactation. Figure I. Temporal stages of deficiency leading to the appearance of deficiency Rate and type of production. Different signs (adapted from Suttle 1987). production systems require different

17 DETECTION AND TREATMENT OF MINERAL NUTRITION PROBLEMS IN GRAZING SHEEP

Table I. Published values for factorially derived estimates for minerals. Values are expressed as amounts per kg dry diet.

Source Type of sheep Type of diet Weight Weight Na Mg Ca P Cu Zn (kg) gain/loss g/kg g/kg g/kg g/kg mg/kg mg/kg

NRC Replacement M/Da = 10, 30 227 g/d 5.3 2.2 ( 1985) ewe lambs 65% forage, 35% concentrate Replacement MID = 10, 40 182 g/d 4.2 1.8 ewe lambs 65% forage Replacement MID =8.8, 50-70 115 g/d 3 1.6 ewe lambs 85% forage Ewes MID =8.4, 70 10 g/d 2 2 100% forage Ewes, first MID =8.4, 70 30 g/d 2.5 2 third gestation 100% forage Ewes, last third MID =8.8, 70 180 g/d 3.5 2.3 gestation 85% forage Ewes, lactation M/D= 10, 70 -25 g/d 3.2 2.6 65% forage ARC Castrate lambs DMlb 0.31 kg/d, 20 o g/d 1.8 1.2 1.5 1.2 ( 1980) qc =0.6 DM10.76 20 200 g/d 1.1 1.1 4.5 2.5 2 32-36 DM10.53 40 o g/d 2.1 1.5 1.8 1.4 3 DMI 1.23 40 200 g/d 1.1 I 3.2 1.8 4 27-48 Ewes, single DMI 1.03 kg/d, 75 2.3 1.3 1.8 1.9 lamb, first third q =0.6 gestation Ewes, last third DMII.4 75 1.7 1.3 2.8 2.2 7 20-24 gestation Ewes, lactation DM12.2 75 2.0 L milk/day 1.4 1.5 3 2.8 5 25-32 All classes 30 Minson Castrate Unspecified 20 o g/d 0.9 (1990) lambs 20 200 g/d 6.6 40 o g/d 1.1 40 200 g/d 3.2 SCA Unspecified MID =6 o g/d I 1.2 ( 1990) MID = 10 o g/d 2 2.1 MID = 10 200 g/d 3.2 1.7 a MID is metabolisable energy in MJ per kg dry matter. A value of ~ 10 represents a good quality diet. A value of 6 represents a poor quality diet of low digestibility. b DI"ll = dry matter intake. C q = diet metabolisable energylgross energy. The gross energy of most ruminant diets is between 18 and 19 MJ/kg.

18 UNDERSTANDING THE MIf'IERAL REQUIREMENTS OF SHEEP- c.L. WHITE

amounts of minerals. Wool contains higher Dietary factors concentrations of sulfur, selenium and zinc than most other body tissues, and is partic­ The form of mineral in the diet and the ularly sensitive to deficiencies of these ele­ presence or absence of synergistic and ments. Likewise, milk contains high levels antagonistic compounds and elements are of calcium and sodium, thereby increasing of prime importance in determining whether the requirement during lactation by almost or not the sheep meets its mineral require­ 50% (AFRC 1991). The requirement ments. Perhaps the best known interaction expressed as the amount per kg of diet is between copper, molybdenum and sulfur. changes to a lesser extent during lactation Figure 2, derived from equations of Suttle than the requirement expressed as amount and McLaughlin (1976), shows that copper per day because of the increased feed availability is a function of sulfur and molyb­ intake associated with lactation. Nonethe­ denum concentration in pasture. This inter­ less, high producing dairy cows are unable action has a larger bearing on the copper , to meet their requirement for calcium from status of sheep than does the copper con­ the diet and draw on calcium from bone centration of pasture. A herbage concentra­ (AFRC 1991). The concentration in milk of tion of 10 mg/kg copper can cause macro elements such as sodium, calcium, swayback in one area and copper toxicosis phosphorus and potassium remains rela­ in another, simply by virtue of the differ­ tively constant, so that these minerals can ences in molybdenum and sulfur status of be spared under conditions of limited the herbage. supply only by reducing milk production 5 ~------~ (McDowell 1992). l Herbage molybdenum (mg/kg) Rapidly growing sheep have a higher ~ 4 15 daily requirement for most minerals than ~ 'ffi 3 sheep of similar age at maintenance by ca> virtue of the demands for mineral accretion 2 &a. o in growing tissues. Since higher growth t.) ~ 1 rates are usually associated with diets of ca Q) higher digestibility, requirements expressed CS 0 on a dietary concentration basis need to be 1.0 1.5 2.0 2.5 3.0 3.5 4.0 specified for each level of production and Sulfur in herbage (g/kg DM) each level of metabolisable energy (Table 1). There is evidence, fQr calcium at least, Figure 2. The effect of herbage concentrations of that rapidly growing sheep compensate for sulfur and molybdenum on the the increased demand by having a higher availability of copper to ruminants (from efficiency of absorption than sheep at Suttle 1983). maintenance (Braithwaite and Riazuddin 1971). Another notable example of an interaction is the effects of potassium fertilizer, protein,

19 DETECTION AND TREATMENT OF MINERAL NUTRITION PROBLEMS IN GRAZING SHEEP

sodium, calcium and fats on magnesium duces magnesium oxide (MgO). If the tem­ availability (Henry and Benz 1995) and perature is too high (> 11 oooe, 'dead burnt') potassium and protein on grass tetany the availability is little different from mag­ (Mayland and Grunes 1979). Poor absorp­ nesite, whereas at temperatures between tion of magnesium from forage is consid­ 800 and 1100°C ('light burn' MgO) the ered to be the most important factor magnesium availability is increased by a causing magnesium deficiency (Wilson and factor of three above unprocessed magnes­ Grace 1978), and the increased use of ite. potassium fertilizer has a large effect on Calcium oxalates have low availability to increasing the incidence of hypomagnesae­ sheep and they are present in high concen­ mia (Grace 1983). The effects of pasture trations in some forages, particularly tropi­ magnesium, potassium, sodium, calcium cal grasses. Oxalates have been suggested and protein on the incidence of grass tetany as a cause of hypocalcaemia in Latin in cattle in the Netherlands are shown in America (Kiatoko et al. 1978) and transit Figures 3 and 4. tetany in Australia (Minson 1990). Lucerne (Medicago sativa) contains 20-30% of 50 calcium as calcium oxalate (Blaney et al. 1982). ~ 40 ;>. c: co § 30 '0 ID 1.20 () 20 c: ID "0 .(3 10 E 1.00 0 :::::J 0.80 1.0 1.5 2.0 2.5 3.0 3.5 ~ E Forage K/(Ca + Mg) E- O> 0.60 ~ E Figure 3. The effect of the pasture concentration :::) Q3 of potassium, calcium and magnesium ({) 0.40 on the incidence of grass tetany in cattle in the Netherlands (Mayland and 0.20 Grunes 1979; Kemp and 't Hart 1957). o

In addition to interactions, the chemical 0.05 0.10 0.15 0.20 0.25 0.30 0.35 form of the mineral is critical in determining Forage Mg (%) availability. Availability of magnesium from ground magnesite and dolomite is less than Figure 4. The effect of protein and potassium on serum magnesium half that from magnesium sulfate (Henry concentration and on the risk of grass tetany in cattle (from Mayland and Benz 1995). Heating magnesite pro- and Grunes 1979). CP =crude protein.

20 UNDERSTANDING THE MINERAL REQUIREMENTS OF SHEEP- c.L. WHITE

Determining the Minimum physiological range. In practice, the critical Requirement for a Nutrient value is expressed as a narrow range, to account for genotypic/phenotypic variabil­ Requirement is a function of some predeter­ ity. In plants, for example, the critical zinc mined measure of response, be it enzyme concentrations for growth of subterranean activity, growth or wool production. The clover, lucerne and perennial ryegrass are initial response of a deficient organism to 12-14, 16-20 and 10-13 mg/kg, respec­ increasing levels of mineral can be tively (Smith 1986). Measurements are described using either a dose-response or made on a specific plant part during a spe­ Mitscherlich relationship (Figs 5, 6). The so­ cific growth phase. In the case of zinc the called clinical range is where signs of defi­ youngest open leaf of early vegetative ciency are easily recognisable. The marginal growth is used. For sheep, critical values or subclinical range is where pathological can be applied to diets but they are most signs of deficiency are not evident but pro­ useful when they refer to concentrations in duction is impaired. Marginal deficiency the target tissue because this accounts for constitutes the majority of cases. The critical most of the variability associated with differ­ value, seen on the shoulder of the curve in ences in availability. Fig. 5, describes the concentration of a From data using semi purified diets, the mineral in a particular feedstuff or animal 95% critical values for zinc for growth of tissue at which growth or production are a sheep are 6.7 Jlmol/L in plasma (Fig. 6) or predetermined proportion of maximum 10 mg/kg DM in the diet based on Mitscher­ (e.g. 90%). Iich relationships (White 1993). For wool The critical value is determined experi­ growth they appear to be about 20% higher, mentally with all other nutrients and condi­ but the data are limited to one experiment tions non-limiting and within the normal (White et al. 1994). In fact few estimates have been made of critical values for miner­ als for sheep because of the cost associated with the purified diets and the need for con­ Deficient Adequate Toxic tamination-free animal facilities. 100

Recom mended Published Tables of requ irements Requirements

Inspection of Table 2 shows that some large differences exist between authorities with value respect to recommended requirements. For o L-____ example, the NRC (1985) requirements for Concentration (in diet or tissue) selenium are between two- and seven-fold Figure S. The dose-response relationship for minerals and animal production, greater than those of other countries. Like­ showing the critical value. wise, the Australian values (SCA 1990) for

21

1-- DETECTION AND TREATMENT OF MINERAL NUTRITION PROBLEMS IN GRAZING SHEEP

phosphorus are significantly lower than There are two main reasons for these dif­ those from other countries, and calcium ferences. The first is the use of different requirements vary greatly between France absorption coefficients. The higher esti­ (INRA 1978) and the U.K. (AFRC 1991) mate of requirement for calcium by INRA (Table 3). (7.3 gjkg) versus the ARC (3.2 gjkg) (Table 3) is due mainly to the adoption of different values for absorption efficien­ 250 '" '" o . cies-INRA using 0.45 and ARC 0.68. The >:; 200 <1l second reason for different values for "0 9 150 requirements between different authorities (J) "§ is the varying interpretations as to what the .r:; 100 tables actually represent. The Australian ~ e • (SCA 1990) values for phosphorus require­ (9 50 • 0 ment are lower than others because they 0 are considered to be minimum requirement 0 3 6 9 12 15 18 21 values. The SCA (1990) attempted to esti­ Plasma or serum zinc (I-lmoI/L) mate true minimum values and considered that those of the ARC (1980) and NRC Figure 6. Mitscherlich relationship for plasma and (1985) were allowances rather than serum zinc concentration versus growth rate of sheep using purified requirements because they included a diets. Symbols for plasma zinc are 0 safety factor. White (1993) and. Mills et al. (1967), In human nutrition a distinction is made and for serum zinc, .& Ott et al. between published tables of daily allow­ ( 1965). ances and the minimum requirement of a

Table 2. Published values for dietary mineral requirements for sheep. Where a range is given the lower values are for maintenance and the higher for growth and lactation.

Sourcea Na K Mg Ca P S Cl Cu Co Se Ib Zn Mn Fe g/kg g/kg g/kg g/kg g/kg g/kg g/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg

N.Z. 0.9 3.6 1.2 2.9 2 1.5 5 0.11 0.03 0.2 25 25 30 u.s. 0.9-1.8 5-8 1.2-1.8 2-8.2 1.6--3.8 1.4-2.6 7-11 0.1-0.2 0.1-0.2 0.1-0.8 20--33 20-40 30--50

Aus 0.7-0.9 5 1.2 1.5-2.6 1.3-2.5 0.7-0.9 5 0.11 0.05 0.5 20--30 15-25 40

U.K. 0.8-2.7c 0.8-1.7 1.4-4.5 1.2-3.5 1-8.6 0.08-0.1 0.03-0.05 0.15-0.5 30 25 30 a N.Z. = New Zealand (Grace 1983). U.S. = USA (NRC 1985). Aus = Australia (SCA 1990). U.K. = United Kingdom (ARC 1980). b Absence of goitrogens.

C For diets of I I MJ/kg metabolisable energy.

22 UNDERSTANDING THE MINERAL REQUIREMENTS OF SHEEP - c.L. WHITE

nutrient. Allowances are designed to meet 2. by supplementing practical diets, includ­ the requirements of practically all people ing pastures, that have a low mineral and so are set well above minimum require­ content and noting whether supplemen­ ments, usually at two standard deviations tation improves animal performance; (Black 1986). This distinction is not so clear 3. by factorial analysis. in animal nutrition. The NRC (1985) and Each method has advantages and disad­ INRA (1978) make no specific reference to vantages, which are summarised in Table 4. safety margins, but apparently regard the values as allowances rather than minimum Experiments using semi-purified diets requirements (see AFRC 1991). The differ­ Animal house experiments using semi­ ences between estimates of dietary require­ purified diets are necessary to determine ments are in fact mainly a reflection of critical values of minerals, such as that differences in safety factors. shown in Figure 6 for zinc. In this type of Table 3. Estimates of dietary calcium and phos­ work it is important to have more than three phorus requirements. treatment levels, at least one of which is close to the critical value. The data can then Source caa pa be described either by a Mitscherlich or g/kg DM g/kg DM dose-response relationship and an estimate made of the critical value. Unfortunately, (1965) ARC 5.5 2.8 many experiments fail to meet these criteria INRA (1978) 7.3 2.9 and the results are of limited value for ARC (1980) 3.2 1.9 determining marginal or critical require­ NRC (1985) 4.6 2.4 SCA (1990) 3.2 1.7 ments. AFRC (1991) 3.2 2.9 Purified diets tend to be expensive, as are the animal facilities required to minimise a For a 40 kg sheep at 200 g/day fed a roughage-based contamination. For this reason there are few diet of approximately 10 MJ metabolisable energy (ME). published data on the critical requirements Values are estimated where specific concentrations are for minerals, and other methods tend to be not given. more frequently used to estimate minimum requirements. Estimating Values of Requir.ements Experiments using practical diets Estimates of requirements in publications In this type of experiment all animals are such as those shown in Table 2 have been typically fed the same base diet or graze the derived in three ways: same area, and a treatment group receives 1. by feeding animals with synthetic diets of a single level of a mineral supplement. If the known mineral concentration and meas­ treated group performs better than the uring their response to different levels of untreated group then the base diet is con­ mineral; sidered to be deficient. This approach

23 DETECTION AND TREATMENT OF MINERAL NUTRITION PROBLEMS IN GRAZING SHEEP cannot define requirements accurately, but (1985) have proposed a method of taking can indicate whether a certain level of this uncertainty into account by plotting mineral is adequate or not. However, when probability of response against a diagnostic the results of several trials are combined, a value, such as blood selenium. This is pattern emerges defining the obviously defi­ shown in Figure 7 using stylised data on cient and adequate levels. An overlapping responses of calves to selenium supple­ area of marginal deficiency may remain ments (taken from LangJands et al. 1989). where responses to supplement are incon­ At a blood selenium concentration of 0.25 sistent or cannot be explained. Clarke et al. /-LmolfL there is a 70% chance of obtaining

Table 4. Advantages and disadvantages of various methods of estimating requirements.

Method Advantage Disadvantage

Animal house experiments Clearly defines requirements under a set of Cost. Experiments require expensive dietary with purified diets conditions where contamination is controlled. ingredients and contamination-free animal facilities.

Suitable for detailed measurements of Results may not apply to the practical situation due absorption and excretion using to the use of artificial diets. radioisotopes.

Experiments using practical Cheaper diets and animal facilities Difficult to produce a severe deficiency because of diets compared with using purified diets. the natural diets. This limits the ability to define critical requirements accurately.

Gives a useful indication of the deficient and Difficult to control and monitor contamination. adequate range of an element in a practical situation. Difficult to control variables (such as disease and weather) which may mask a possible response to the element under investigation.

limit on what metabolic information can be derived. Cannot use radioisotopes and it may be difficult to collect urine and faeces.

Factorial analysis Results can be applied to any breed and Data requirements are high. It requires extensive production system. basic information that can only be derived from animal house experiments.

For several elements the variability associated with the input data make the output predictions of limited value.

24 UNDERSTANDING THE MINERAL REQ(J[REMENTS OF SHEEP- c.L. WHITE

a response of 10 gjday to a supplement, but generally possible with trace elements such only a 15% chance of obtaining a response as cobalt and selenium because individual of 90 gjday. sheep can be treated within a control flock. Both the purified diet approach and prac­ The deficient control sheep should be moni­ tical response trial suffer the disadvantage tored over time for contamination resulting in that results apply only to that type of from excreta from the treated sheep. It is animal under those feeding conditions. To also important to control for other more obtain a complete picture the experiments severe nutritional deficiencies by either have to be repeated for all classes of live­ checking status or supplying supplements. stock under a wide range of. conditions. For example, it is likely that sheep will show Experiments using practical diets require a diminished or nil growth response to a special controls. The experiments must be mineral supplement if the energy intake is carried out using appropriate animals at an also limiting. appropriate time of year (usually when pro­ If macromineral deficiencies are sus­ duction is highest) and using an appropriate pected it is usually not possible to run the experimental design. Ideally the sheep treated sheep within the control flock should be run together in the same paddock because of the difficulty of supplying gram and a subset treated with minerals. This is quantities of minerals every day to individ­ ual grazing animals. In this situation sheep should be allocated to replicated plots or rotated through paddocks at frequent inter­ 0.8 vals to control for possible paddock differ­ ences. The latter method is likely to lead to >- co contamination of the pastures consumed by :!2en x 0.6 deficient control sheep and this must be tU Q) closely monitored. Experiments should be (/) c: 8. repeated over several years to account for (/) 0.4 ~ variations in response due to annual differ­ co ences in rainfall and pasture production. It is '0 also preferable to use more than one geno­ ~ 0.2 15 type in a factorial design to account for ~ a::0 genetic differences in requirements and 0.0 response. A major consideration in this type of

0 63 126 190 253 316 380 experiment is the power of the design. In designing response experiments it is impor­ Whole blood selenium (nmoI/L) tant to consider the expected size of Figure 7. Probability of a response to a selenium supplement in calves at a response and the coefficient of variation given concentration of blood selenium. From Langlands et al. (CV) of the parameter being measured. If ( 1989). too few animals are tested then the results

25 DETECTION AND TREATMENT OF MINERAL NUTRITION PROBLEMS IN GRAZING SHEEP

can be misleading because of a type " sta­ the animal. True absorption is influenced tistical error-falsely accepting the null greatly by the age of the animal, by the hypothesis. An example of the effect of mineral status of the animal and diet, by the sample size on the probability of rejecting level of feed intake and by the presence of the null hypothesis when it is false is given in other interacting factors in the diet. Figure 8. For Iiveweight, if only 15 sheep per The main advantage of the factorial group are compared in a trial where the var­ method is that mineral requirements can be iance is 16 kg, then the probability of calculated for any type and level of produc­ making a type" error is about 75% when tion. The main disadvantage is the paucity treatment differences are 2 kg. Even with of accurate data, especially for absorption n=30 there is only a 50% chance of correctly coefficients of the trace elements. This detecting a true treatment response of 2 kg. means that for some minerals precise esti­ To be 80% confident of not making a type 11 mates of minimum requirements cannot be error a sample size of 70 sheep per group is made, and so safety margins are adopted required (Steel and Torrie 1981). The sim­ which make the estimates of little practical plest way to reduce the number of animals value. Nonetheless, the factorial method is without losing power is to reduce the vari­ a powerful method for estimating mineral ance, preferably by covariance adjustment requirements and a summary table of using pretreatment measurements.

The factorial method 1.0 The factorial method for estimating requirements is based on energy and protein models and estimates the dietary 0.8 need for a mineral by adding up the com­ ponents of maintenance and growth or pro­ Q) 3: 0.6 duction and dividing by the coefficient of 0 Cl.. absorption. Net requirements (amounts/ day) are defined as: 0.4

Mn = Me + Mg + Mw + Mc +- MI·

Me is mineral of endogenous origin lost in 0.2 faeces and urine, and Mg,w,c,1 are minerals sequestered for liveweight gain, wool, con- . o 5 10 15 20 25 ceptus and milk. This is represented sche­ Variance (kg) matically for phosphorus in Figure 9. Gross or dietary requirements are calculated by Figure 8. The effects of variance and sample size on the power of experimental dividing net requirements by the coefficient design. The data are for three flocks of sheep (numbering 15, 30, or of true absorption. This is the fraction of 70) weighing 40 kg and with a minimum detectable difference of 2 kg mineral ingested that can be absorbed by (5% of liveweight).

26 UNDERSTANDING THE MINERAL REQUIREMENTS OF SHEEP - CL. WHITE published requirement values is shown in In practice, a difference in growth between Table 1. animals of the same age is usually due to a The important thing to note is that the difference in diet quality and so mineral dietary need for minerals varies with the requirements for animals at maintenance level of production and quality of the diet. should be assessed in relation to a low Mineral requirements are higher for growth quality diet. than maintenance, and higher for highly digestible diets than for diets of low digesti­ Conclusions bility (when expressed on a per kg of diet basis). For example, the recommended It can be seen that published estimates of dietary concentration for calcium decreases requirements need careful interpretation by half when the metabolisable energy value and should not be applied to grazing sheep of the diet falls from 10 to 6 MJjkg OM (SeA without qualification. Assessing mineral 1990) at liveweight maintenance (Table 1). status by comparing analysed dietary con-

MAINTENANCE PRODUCTION

Faecal Urine Tissue Wool Foetus Milk loss loss growth growth

0.014 g/kg BW

Net requirement

(1.27 glday for pmgnancy) j (Net requlrernenVabsorpUon coefficient)

Gross requirement

(2.2 Wday) I(Gross requlremenVdry matter Intake)

Dietary allowance (1.6 g/kg OM)

Figure 9. Factorial estimation of the phosphorus requirements of the pregnant ewe. The assumptions are that the ewe eats lA kg DM and the absorption coefficient of phosphorus is 0.6. From Grace (1983).

27 DETECTION AND TREATMENT OF MINERAL NUTRITION PROBLEMS IN GRAZING SHEEP centration with published estimates of Clarke, R.G., Wright, D.F. and Millar, K.R. 1985. requirement is of limited value in grazing sit­ A proposed new approach and protocol to uations because of the difficulty in knowing define mineral deficiencies using reference curves. Cobalt deficiency in young sheep is what the sheep selects and how much of the used as a model. New Zealand Veterinary mineral the sheep absorbs. It follows that Journal, 33, 1-5. single estimates of requirement expressed Grace, N.D., ed., 1983. The Mineral Require­ as amounts per kg of diet need to be inter­ ments of Grazing Ruminants. Occasional Pub­ preted as recommendations only and lication No. 9, New Zealand Society of Animal should not be used in isolation to indicate Production. whether a sheep is meeting its requirements Henry, P.R. and Benz, S.A. 1995. Magnesium for a mineral or not. An understanding of bioavailability. In: Ammerman, e.B., Baker, how the values were derived assists in D.H. and Lewis, A.J., ed., Bioavailability of applying the values in practice. Nutrients for Animals: Amino Acids, Minerals and Vitamins. New York, Academic Press, 201-237. References INRA (Institut National de la Recherche Agrono­ mique) 1978. Alimentation des Ruminants. AFRC (Agricultural and Food Research Council) Versailles, INRA Publications. 1991. A reappraisal of the calcium and phos­ Kemp, A. and 't Hart, M.L. 1957. Grass tetany in phorus requirements of sheep and cattle. grazing milking cows. Netherlands Journal of Technical committee on responses to nutri­ Agricultural Science, 5, 4-17. ents, report number 6. Nutrition Abstracts and Kiatoko, M., McDowell, L.R., Fick, K.R., Fonseca, Reviews, Series B: Livestock Feeds and H., Camacho, J., Loosli, J.K. and Conrad, J.H. Feeding Vol. 61, 573-612. 1978. Mineral status of cattle in the San Carlos ARC (Agricultural Research Council) 1965. In: Region of Costa Rica. Journal of Dairy The Nutrient Requirements of Farm Livestock, Science, 61, 324-330. No. ]: Ruminants. London. HMSO, 14-85. Langlands, J.P., Donald, G.E., Bowles, J.E. and - 1980. In: The Nutrient Requirements of Rumi­ Smith, A.J. 1989. Selenium concentration in nant Livestock. Slough, Commonwealth Agri­ the blood of ruminants grazing in northern cultural Bureaux, 256-262. New South Wales. 3. Relationship between Black, A.E. 1986. The use of recommended blood concentration and the response in Iive­ daily allowances to assess dietary adequacy. weight of grazing cattle given a selenium sup­ Proceedings of the Nutrition Society, 45, plement. Australian Journal of Agricultural 369-381. Research, 40, 1075-1083. Blaney, B.J., Gartner, R.J.W. and Head, T.A. McDowell, L.R. 1992. Minerals in Animal and 1982. The effect of oxalate in tropical grasses Human Nutrition. New York, Academic Press. on calcium, phosphorus and magnesium' Mayland, H.F. and Grunes, D.L. 1979. Soil­ availability. Journal of Agricultural Science, climate-plant relationships in the etiology of 99,533-539. grass tetany. In: Rendig, V.V. and Grunes, D.L., Braithwaite, G.D. and Riazuddin, S.H. 1971. The ed., Grass Tetany. Madison, American Society effect of age and level of dietary calcium of Agronomy, 123-175. intake on calcium metabolism in sheep. Metson, A.J., Saunders, W.H.M., Collie,T.W. and British Journal of Nutrition, 26, 215-225. Graham, V.W. 1966. Chemical composition of

28 UNDERSTANDING THE MINERAL REQUIREMENTS OF SHEEP - c.L. WHITE

pastures in relation to grass tetany in beef symposium of the International Network of breeding cows. New Zealand Journal of Agri­ Feed Information Centres. Farnham Royal, cultural Research, 9, 410-436. Commonwealth Agricultural Bureaux. Mills, CF., Dalgarno, AC, Williams, R.8. and -1987. The nutritional requirement for copper in Quarterman, J. 1967. Zinc deficiency and the animals and man. In: Howell, J. McC and zinc requirements of calves and lambs. British Gawthorne, J.M., ed., Copper in Animals and Journal of Nutrition, 21, 751-768. Man, Vol. 1. Boca Raton, CRC Press Inc., 21 Minson, D.J. 1990. Forage'in Ruminant Nutri­ 43. tion. San Diego, Academic Press. Suttle, N.F. and McLaughlin, M. 1976. Predicting the effects of dietary molybdenum and sulphur NRC (National Research Council) 1985. Nutrient on the availability of copper to sheep. Pro­ Requirements of Sheep. 6th edition. Washing­ ceedings of the Nutrition Society, 35, 22A- ton DC, National Academy Press, 19-20. 23A. Ott, E.A., Smith, W.H., Stob, M., Parker, H.E., Underwood, E.J. 1981. The Mineral Nutrition of Harrington, R.B. and Beeson, W.M. 1965. Zinc Livestock. Slough, Commonwealth Agricultu­ requirement of the growing lamb fed a purified ral Bureaux. diet. Journal of Nutrition, 87,459-463. Wiener, G. and Field, AC 1970. Genetic varia­ SCA (Standing Committee on Agriculture) 1990. tion in copper metabolism of In: Mills, Feeding Standards for Australian Livestock: CF., ed., Trace Element Metabolism in Ruminants. Melbourne, CSIRO Publications, Animals. Edinburgh, E&S Livingstone, 92- 175-181. 102. Smith, F.W. 1986. Pasture species. In: Reuter, White, CL. 1993. The zinc requirements of D.J. and Robinson, J.B., ed., Plant Analysis. grazing ruminants. In: Robson, AD., ed., Zinc Melbourne, Inkata Press. in Soils and Plants, Development in Plant and Steel, R.G.D. and Torrie, J.H. 1981. Principles Soil Sciences, Vol 55, London, Kluwer Aca­ and Procedures of Statistics-a Biometrical demic Publishers, 197 -206. Approach. 2nd edition. Singapore, McGraw White, CL., Martin, G.8., Hynd, P.l. and Hill International. Chapman, R.E. 1994. The effect of zinc defi­ Suttle, N.F. 1974. A technique for measuring the ciency on wool growth and skin and wool his­ biological availaility of copper to sheep using tology of male Merino lambs. British Journal hypocupraemic ewes. British Journal of Nutri­ of Nutrition, 71,425-435. tion, 32, 395-405. Wilson, G.F. and Grace, N.D. 1978. Pasture -1983. Assessment of the mineral and trace magnesium levels and milk production in element status of feeds. In: Robards, G.E. and dairy cows. New Zealand Journal of Experi­ Packham, R.G., ed., Proceedings of the second mental Agriculture, 6, 267 -269.

29 Non-dietary Influences on the Mineral Requirements of Sheep

Neville F. Suttle

Moredun Research Institute Edinburgh EH 177JH Scotland, U.K.

Outline

Genetic variation in mineral metabolism Magnesium Phosphorus Copper Impact of nematode infections of pasture on mineral requirements Copper Sodium Phosphorus Effects of demand on critical pathways Exercise Cold stress Other examples Redistribution of minerals within the body Hypocalcaemia prevention in lactating cows Redistribution at parturition Magnesium Sodium Zinc Assessment of mineral status Three-tier assessment system Dose-response trial References

31 DETECTION AND TREATMENT OF MINERAL NUTRITION PROBLEMS IN GRAZING SHEEP

atural selection within livestock popu­ lower mineral intakes than those associated N lations exposed to mineral imbalances with disorders in the field. in local forages and crops has resulted in Likewise, biochemical indices of mineral adaptations which protect most individuals status in the bloodstream or tissues decline from temporary deficiencies or excesses. to limits rarely seen on farms before health Much has been written about the homeo­ is impaired. Since normal ranges for clinical static and homeorhetic processes involved biochemistry are also drawn largely from (e.g. Kirchgessner 1993) but less has been the results of indoor experiments, the basis said about their genetic control or their for defining and controlling mineral­ influence on the incidence, diagnosis and responsive disorders is unsound. The object control of disorders caused by mineral of this paper is to bridge the gap between imbalance. the indoor experiment and field observa­ Such disorders are most likely to arise tions by focusing on the marked influences when sudden environmental or physiologi­ of non-dietary factors on mineral require­ cal changes cause abrupt changes in ments. mineral requirements or when homeostatic mechanisms are not fully functional. The Genetic Variation in Mineral classical methods for studying mineral Metabolism imbalances are of limited relevance to these disorders because experimenters usually Variation in mineral status is often a striking rely on the establishment of a steady state. feature of both experimental and field A refined diet, limiting with respect to a studies with ruminants. Since the variation single mineral, has commonly been fed to is often repeatable and partly heritable individually-penned, castrated male or (Table 1), it should influence the way barren female animals which tolerate far mineral experiments are designed and eval-

Table I. Magnitude (M) of 'genetic' variation in mineral status where M = highest value for breed (B). identical twin (T) or quadruplet (Q) divided by the lowest value.

Element Species Class Parameter M Reference

Mg Cattle T Availapilitya 3.3 Field and Suttle (I 979) Mg Sheep B Availabili,tya 1.3 Field et al. (1986) P Cattle T P in urine 12.3 Field and Suttle (1979) P Sheep Q P in urine 4.0 Field et al. (I 986) Cu Sheep B Cu in liver 2.6 Woolliams et al. (1982) Cu Sheep B Cu in plasmab 2.5 Wiener et al. (1978) a Urine Mg +- intake of Mg. b Rate of repletion.

32 /'ION-DIETARY INFLUENCES ON THE MINERAL REQUIREMENTS OF SHEEP - NF. SUTTLE

uated and also the way field problems are The efficiency of phosphorus absorption in solved. ruminants has a two-fold influence on phos" phorus requirements because it determines Magnesium the efficiency of phosphorus recycling via saliva and hence endogenous losses. The Students of magnesium metabolism in most efficient individual users of phos­ ruminants have long appreciated the need phorus were calculated to have phosphorus to remove repeatable individual variation requirements about 30% below the ARC when looking for treatment effects by the (1980) minimum requirement for ewes use of Latin Square designs (e.g. Suttle and during lactation (Field ] 98]). As with mag­ Field 1967). Experiments with just three nesium, significant differences in urinary pairs of monozygotic twin cows have shown phosphorus excretion were found between clear genetically controlled differences in identical twin heifers (Field and Suttle ] 979) the efficiency of magnesium absorption and between offspring from different rams (Field and Suttle 1979). Awareness of such (Field et al. 1986), and there was a four-fold influences contributed to the Agricultural difference between breeds (Field et al. Research Council's decision (ARC 1980) to ] 986). The precision of experiments with introduce a safety factor whereby dietary phosphorus can also be improved by allow­ allowances of ruminants for magnesium ing for genetic variation in phosphorus were set 70% above estimated minimum metabolism (e.g. Field et al. ]984). requirements to cater for the most vulnera­ ble individual. It would be surprising if prac­ Copper tical magnesium deficiency problems in ruminants could not be reduced by genetic Differences in blood copper concentra­ selection using a simple index such as the tions between breeds of sheep grazing the magnesium:creatinine ratio in urine of the same pastures led to the discovery of sub­ sire. Significant differences in urinary mag­ stantial breed differences in the efficiency of nesium excretion between the offspring of copper absorption (Wiener et al. ] 978; different sires have been reported in sheep Woolliams et al. 1982). The heritability of with an estimated heritability of 0.60 (Field the factor(s) controlling copper absorption et al. 1986). were high enough for substantial increases in copper status to be achieved by sire Phosphorus selection for six male generations based on plasma copper concentrations at a young Studies with sets of four identical, chi­ age (Woolliams et at. 1986a,b). Breeds that maera-derived sheep showed that efficiency used copper efficiently, such as the Texel, of phosphorus absorption ranged from 0.63 were vulnerable to copper poisoning when to 0.79 of phosphorus intake between sets, housed (Woolliams et al. ] 982) whereas and variation within a wider population was those using copper inefficiently, such as the estimated to be similar (Field et al. 1984). Scottish Blackface, were vulnerable to defi-

33 DETECTION AND TREATMENT OF MINERAL NUTRITION PROBLEMS IN GRAZING SHEEP

ciency when grazed (Woolliams et al. mentation of the diet or stock presents eco~ 1986a,b). The requirements of the Texel nomic (e.g. phosphorus) or practical (e.g. and Scottish Blackface probably differ by a sodium) problems. factor of two or more (Suttle 1987). The messages are the same as for magnesium Impact of Nematode Infections and phosphorus: allowing for initial varia­ of Pasture on Mineral tion in and the repeatability of copper status (e.g. use of initial liver biopsy concentra­ Requirements tions and covariance analysis) improves the Pasture nematode infections increase precIsion of experimentation; selection mineral requirements and they are endemic within or between breeds can solve prob­ in all pastoral systems. lems of copper deficiency and excess (Woolliams et al. 1982, 1986a,b). However, Copper selection for improved status for one mineral (e.g. magnesium) may result in In defining the role of continuous larval lowered status of another, e.g. phosphorus nematode infection in the pathogenesis of (Field and Suttle 1979). diarrhoea in a flock of Finnish Landrace The presence of widespread, large genetic (FL) sheep, the effects of discontinuous and variation in mineral metabolism in popula­ continuous anthelmintic (albendazole) tions is unique to ruminants and it is note­ treatment were compared against no treat­ worthy that the rumen plays a vital role, ment. Effects of treatment on diarrhoea directly or indirectly, in the absorption of were small and late to develop (Suttle and each of the elements cited: for magnesium, McLean 1995) but plasma copper the rumen is the principal site of absorption; increased markedly in both young, non­ for phosphorus, rumination is responsible reproducing females and lactating ewes for extensive phosphorus recycling via (Fig. 1), suggesting that copper require­ saliva; for copper, the rumen is the site of ments had been increased by nematode antagonisms which lower availability (e.g. infection. The initial hypocupraemia was Suttle 1987). Genetic variation may be unexpected since the pasture contained linked to selection pressure arising from sufficient copper (8-10 mg copper/kg dry diverse nutritional conditions, endemic defi­ matter) to meet their requirements in the ciency favouring the evolution of efficient absence of antagonisms from molybdenum users, and endemic toxicity the evolution of «2 mg/kg DM) or iron «1 g/kg DM) (e.g. inefficient users of minerals. It would be sur~ ARC 1980). The fact that a continuous prising if there were not marked variations release bolus was more effective than in mineral metabolism within species in drenching with anthelmintic once every 4 many parts of the world, given the vast land weeks suggests that larval infection was areas and the diversity of agricultural contributing to the impairment of copper systems used to grow sheep. Exploitation metabolism. Furthermore, immune year~ could be of particular value where supple- lings benefited as much as immunosup-

34 NON-DIETARY iNFLUENCES ON THE MINERAL REQUIREMENTS OF SHEEP - NF. SUTTLE pressed ewes, suggesting that impairment egg output in the ewes (median count 200 can arise as a consequence of immunity as eggs/g fresh weight) suggests that only low well as by physical damage to a poorly worm burdens are needed to impair copper protected gastro-intestinal mucosa. Low metabolism. The quantitative impact of parasitic infection on copper requirements cannot

10 (a) be gauged from these studies but some • Drench given • interesting comparisons can be made. The 9 Bolus repletion rates in yearlings were equivalent ~ • "0 Drench E • to absorption rates of 0.79 and 1.40 mg 8 Untreated -3 0 copper/d (from Suttle 1974) for those :::l 0 7 (\l given drenches and boluses, respectively, E rJ'J Le. a 77% improvement in availability from (\l 6 CL combating the continuous larval challenge. 5 The faster repletion rate of hog gets over ewes grazing the same pasture confirms o 5 10 that lactation increases the copper require­ Weeks ment in terms of copper concentration in the pasture. In an earlier experiment with 12 (b) the FL flock it was noted that the same • Drench given 11 • dose of cupric oxide particles (CuOp) given ~ to two similar groups of lambs, grazing "0 10 E adjoining fields, protected one from hypo­ ..:; 9 :::l 0 cupraemia for at least 150 days and the (\l 8 E other for only 60 days (Suttle and Brebner rJ'J (\l 7 CL 1995). The poorly protected group was 6 more prone to diarrhoea and had an 5 abnormally high plasma pepsinogen con­ centration v 0.8 U/L) (U units) indi­ o 5 10 (1.1 = Weeks cating abomasal parasitism. In previous experiments, a similar reduction in efficacy Figure I. (a) Repletion of plasma copper in of CuOp was obtained by adding 3 mg lactating ewes was hastened by the molybdenum and 3 9 sulfur/kg to the diet administration of anthelmintics, whether of ewes (Suttle 1981). Thus the impact of given in a slow-release bolus or as a infection was equal to that of known potent drench. Diamond symbols indicate the times of drenching. (b) Comparison of antagonists of copper absorption. the repletion rates of plasma copper in Others have reported positive effects of yearlings treated with bolus or drench. anthelmintic treatment (e.g. Judson et a1. Diamonds indicate the times of 1985) and negative effects of abomasal drenching. parasitism (Bang et al. 1990) on liver

3S DETECTION AND TREATMENT OF MINERAL NUTRITION PROBLEMS IN GRAlfNG SHEEP copper reserves in sheep. The new results sufficient sodium (0.1-0.2 g/kg DM) for show that continuous larval infection can lambs by standards (ARC 1980) which induce copper deficiency in sheep grazing have been criticised as being far too high pastures which would normally meet their (Michel 1985). The criticisms are based on copper requirements and at the same time experiments with penned sheep not decrease the efficacy of a common remedy, subjected to continuous larval nematode CuOp. These effects probably reflect a infection in which hormonally-induced decrease in copper absorption but impaired adaptations conserve sodium and prevent entero-hepatic recycling of copper may ill-health at sodium inputs far below the contribute by increasing faecal endogenous published standards (Michel et al. 1988). losses of copper. The net effect may be to An obvious explanation is that physical more than halve the effective supply of damage to the intestinal mucosa by para­ copper from the pasture or the oral supple­ sites limited the ability to conserve faecal ment. sodium. However, compensatory absorp­ tion of sodium should have occurred in the Sodium large intestine, which is usually unaffected by parasitism. The complete explanation Periodically, lambs from the above natu­ may be found in other contrasts between rally infected flock developed extremely low indoor and pasture experiments-the salivary sodium:potassium ratios indicative former involve feeding dry diets low in of sodium depletion (Suttle and Brebner potassium and in these circumstances 1995; N. Suttle and M. Herrero, unpubt.). sheep reduce their extracellular fluid Sodium deficiency was less pronounced in volume by drinking less to maintain sodium seasons when pasture larval infection was concentrations in the extracellular fluid. low (Suttle 1994a) and it was common to When water is consumed principally in the find relationships between saliva sodium: food (grass) and that food is rich in potas­ potassium or potassium, faecal DM (g/kg sium, which increases water intake (Suttle FDM) and/or plasma pepsinogen (PP, U/L) and Field 1967), homeostatic mechanisms of the following kind: may be far less effective, particularly in abomasal parasitism which causes large K = 22.9 + 4.5 pp 0.47 FDM (r 0.34; 82 df) increases in sodium flow at the duodenum These associations suggested that aboma­ (Wilson and Field 1983). sal parasitism and diarrhoea had induced a sodium deficiency. This view is supported. Phosphorus by evidence that although anthelmintic treatment could raise sodium status, a drug Anthelmintic treatment did not affect whose efficacy is lowered by abomasal par­ plasma phosphorus in the FL flock but asitism (albendazole) was relatively ineffec­ homeostatic mechanisms probably mobil­ tive (Suttle et at. 1996). ised extra phosphorus from the skeleton As with copper, the pastures contained and were not compromised by infection of

36 NON-DIETARY INFLUENCES ON THE MINERAL REQUIREMENTS OF SHEEP HF SUTTLE

the gut. Measurements of phosphorus flows occur in beef cattle in the wet season than along the gastrointestinal tract in parasit­ the dry season on pastures of similar phos­ ised sheep have shown that the efficiency of phorus concentration (Winter et al. 1990). absorption of dietary phosphorus is Heavier infection by parasites in the wet reduced, as is that of salivary phosphorus season may have contributed to that sea­ (Wilson and Field 1983; Sown et al. 1989). sonal difference. The combined effect of these changes in Continuous infections of the gut thus one study was to increase estimated phos­ increase requirements for a trace element phorus requirements by 65% (Table 2). (copper), an anionic (phosphorus) and a Parasitic infections of the gut reduce greatly cationic (sodium) macromineral, and it the phosphorus content of the skeleton in would be surprising if they did not affect lambs (e.g. Sykes et al. 1979) and the requirements for most minerals (magne­ impact of nematodiasis on phosphorus sium may be an exception because it is deficiency might be critical if, prior to larval principally absorbed from the rumen). The challenge, skeletal mineral reserves are work of Judson et al. (1985) suggests that depleted through reduction of dietary zinc and cobalt requirements are increased protein or calcium and by lactation. also by worm infections. Good nematode Cattle may be more vulnerable to nema­ control is an essential part of any program tode-induced phosphorus deficiency than to minimise mineral deficiencies in grazing sheep because they have less time to livestock and a flexible approach must be replenish skeletal reserves of minerals maintained in extrapolating from mineral between lactations (e.g. Read et al. 1986). requirements determined in penned, worm­ Studies in the tropics have shown that free animals to needs and risks of deficiency phosphorus deficiency is more likely to in field situations.

Table 2. Effects of intestinal parasitism by T. colubr;(ormis on the efficiency (E) of phosphorus absorption and reabsorption in two sets of identical quadruplet lambs and average extrapolated phosphorus requirements for lactating ewes (75 kg liveweight and yielding 3 kg milk/d).

E saliva P E dietary P P requirement (g/d)

Infection 0 + 0 + 0 +

Set la 0.76 0.60 0.60 0.39 7.9 12.5 Set 2a 0.84 0.25 0.65 0.39 a Unpublished data from A.c. Field: see also Field (1981) and Wilson and Field (1983).

37 DETECTION AND TREATMENT OF MINERAL NUTRITION PROBLEMS IN GRAZING SHEEP

Effects of Demand on Critical ous changes in diet and muscular activity, Pathways and to determine how these changes con­ tributed to muscular damage the experi­ The factorial derivation of mineral require­ ment was repeated with a group of penned ments takes no account of internal, diurnal animals given grass cut from the field. Only or day-to-day variations in demand. Instead, when the grass-fed calves low in selenium the desired input is that which matches were turned out did plasma CK rise. average output and it is hoped that any Throughout both experiments the sele­ short-term variation in demand can be met nium-depleted calves maintained blood by redistributing the body's mineral levels of activity of the selenium-dependent r~serves. With the possible exception of enzyme glutathione peroxidase, which iodine, all minerals have multiple functions would be regarded as grossly deficient « 15 at diverse sites in the tissues. Two examples Ujg Hb). Only when the extra demand of will be given where redistribution of the muscular activity was superimposed did available body minerals may fail to protect muscle damage occur in the low selenium a critical pathway upon which health may calves. The presence of polyunsaturated depend. fats in the spring grass may have contrib­ uted to the development of myopathy but Exercise without exercise they were obviously harm­ less. It would be surprising if exercise did not It is common to allow for the effects of also influence requirements for other nutri­ activity when calculating energy require­ ents affording protection against oxidative ments for livestock (AFRC 1993). For stress (e.g. copper in superoxide dismu­ example, activity adds 12% to the energy tase). requirement of hill ewes carrying a single lamb in mid-pregnancy, when compared to Cold stress housed ewes. The extra energy is consumed during oxidative metabolism and increases Selenium is essential to the activity of the the demand on numerous mineral­ deiodinase enzymes which influence thy­ dependent metabolic pathways. In a study roxine metabolism (Arthur 1993). of selenium deficiency in calves, Arthur Mammals contain two such enzymes, (1988) fed a low selenium diet (0.01 mgjkg Types I and 11, and activities of both are DM) to penned animals for several months suppressed in selenium deficiency. For the without inducing white muscle disease first few weeks of life, brown adipose tissue (monitored via changes in creatine kinase (BAT) in newborn ruminants shows a high (CK) in plasma). When those calves were level of Type I activity and it is probably turned out to graze, plasma CK increased, important for local thermogenesis and the indicating leakage of the enzyme across export of active T3 from BAT to other sites. damaged muscle membranes. The enzyme is there presumably to protect Turn-out was accompanied by simultane- the newborn from hypothermia to which it is

38 NON-DIETARY INFLUENCES ON THE MIf'IERAL REQUIREMENTS OF SHEEP- N.F. SUTTLE

highly prone (e.g. lambs, Eales et al. 1982). around parturition the mobilisation of Type 11 activity in BAT increases during cold calcium appears to be obligatory and cannot stress in rats but the increased activity be halted by putting even a gross excess of cannot be sustained in selenium-deficient calcium into the diet (AFRC 1991). Live­ animals (Arthur et al. 1991). Although the stock have 'learnt' to become less depen­ critical experiments have yet to be per­ dent on the hands that feed them. formed, the offspring of selenium-deficient livestock born outdoors in cold weather Hypocalcaemia prevention in lactating may be more vulnerable to hypothermia cows than those born indoors in a sheltered envi­ ronment. In this case, survival is at stake Genetic selection for high milk yields in and the benefits of ensuring an adequate dairy cattle has created a health problem selenium status could be particularly high. (milk fever) caused by failure to meet the abrupt and enormous increase in calcium Other examples demand with the onset of lactation. The disease can be prevented by improving the Other examples of abrupt increases in net contribution of calcium from the skele­ demand likely to put strain upon critical ton to the extracellular fluid by increasing pathways are: the respiratory burst in pha­ the 'acidity' or anion:cation balance of the gocytes during microbial infection (sele­ diet (Block 1984; Goff et at. 1991; Phillippo nium, Boyne and Arthur 1979; copper, et al. 1994). The 'acid' diet works by modu­ Jones and Suttle 1981); the contraction of lating one of the hormones (1 hydroxy­ the uterine wall during parturition (sele­ cholecalciferol) which controls calcium nium, Suttle 1992); transportation (organic resorption from the skeleton (and calcium chromium, Wright et al. 1994); weaning absorption). However, efficacy may depend ( copper, Suttle 1975). on non-dietary factors. Susceptibility to milk fever increases with age because the Redistribution of Minerals absorption and partitioning of dietary within the Body calcium is changed by a reduction in recep­ tors for 1,25 hydroxy vitamin D in the intes­ The ability of animals to accumulate tine and bone with age (Horst et al. 1990). reserves of minerals during times of plenty Increasing the acidity of the diet of young and to mobilise those reserves during times (1st-3rd parity) cows did not increase their of scarcity lessens the need to ,meet mineral resistance to hypocalcaemia (Van Mosel et requirements on a day-to-day basis and al. 1993). A switch from hay to the more partly explains the tolerance of livestock acidic silage as roughage source should towards diets which 'on paper' are mineral also reduce milk fever in aged cows. deficient. A classic example is the mobilisa­ Other species are less vulnerable than tion of calcium and phosphorus reserves the dairy cow to hypocalcaemia immedi­ from the skeleton. Less well known is that ately after parturition because the require-

39 DETECTION AND TREATMENT OF MINERAL NUTRITION PROBLEMS 11'1 GRAZING SHEEP

ment for calcium in late pregnancy can 14.5±0.4 to 12.0±1.2 mg/L in dry sheep equal that for lactation (e.g. sheep, AFRC given a diet very low in magnesium for 5 1991). Nevertheless, the feeding of acidic days. However, an increase in diet acidity diets (e.g. in sheep, Abu Damir et al. 1990) did not prevent a post-parturient fall in or the culling of older animals may reduce plasma magnesium in dairy cows (Phillippo the risk of disorders associated with hypo­ et al. 1994). Gardner (1973) increased the calcaemia in species such as the sheep, rate of removal of magnesium from the goat and yak. skeleton of sheep by peritoneal dialysis against calcium-free medium but the effect Redistribution at parturition was not reflected by a change in plasma magnesium. Thus, magnesium may have While the skeleton is pre-eminently a been redistributed by a change in acid:base store for calcium and phosphorus, it also balance of the diet but not seen as a change contains most of the body magnesium and in plasma magnesium. substantial fractions of its total sodium and Sodium. There appears to be a shift in the zinc (Table 3). Obligatory resorption of set-point for salivary sodium:potassium bone prior to and after parturition must from 18 to 32 associated with lactation in result in the release of significant amounts sheep (Morris and Peterson 1975). The of these elements in terms of the total mechanism is unclear but the purpose may demand for lactation. be to trap sodium released from the skele­ Magnesium. In milk fever, hypocalcaemia ton in the recycling pool of sodium in the is usually accompanied by hypomagnesae­ rumen and facilitate its transfer to offspring mia which may indicate a parallel shortfall via the sodium-rich milk. Marked reductions in magnesium mobilisation from the skele­ in body sodium after lactation have been ton. Using a pyrophosphate analogue to reported in hill ewes (Field et al. 1968) and inhibit bone resorption, Matsui et al. (1994) such redistribution of body sodium may decreased plasma magnesium from explain the tolerance of ewes to sodium

Table 3. Amounts of mineral which may be mobilised from the skeleton during lactation in sheep and the proportion of the total lactational demand which they would sustain.

Na (g) Mg (g) Ca (g) P (g) Zn (mg)

T otala in skeleton 18.4 10.6 659 280 237 Amount mobilised for lactation 3.8 2.2 135 b 5.7 49 Proportion' (%) of yield sustained 40 69 465 248 181 a From Grace (1983). b From Braithwaite (1983): amounts of other elements calculated pro rata.

C Assuming a total lactational yield in the Merino of 18 kg milk containing 0.4 g Na. 0.18 g Mg. 1.6 g Ca. 1.3 g P and 1.5 mg Zn/kg.

40 NON-DIETARY INFLUENCES ON THE MINERAL REQUIREMENTS OF SHEEP - NF. SUTTLE

depletion (e.g. Michel et al. 1988). Impair­ Clarke et al. 1985; Suttle 1994b; see also ment of sodium recycling by gastrointesti­ Tables 2 and 3 in Paynter in this publica­ nal parasites may limit the effectiveness of tion). The approach is not new but adoption this adaptive mechanism. has not been consistent, and it is not used in the U.K. at present. Adoption of such a Zinc. The tolerance of the in-Iamb ewe to system will slow down the rate at which a zinc depletion (e.g. Masters and Moir 1983) diagnOSiS is made but greatly improve the may depend also partially on the distribu­ precision of that diagnosis and greatly tion of body zinc. If mobilisation of one-fifth reduce the number of recorded diagnoses of of the skeleton's major minerals (calcium 'mineral deficiencies'. and phosphorus) releC\sed a similar propor­ tion of bone zinc, as much as 50 mg zinc could be released, enabling the secretion of Dose-response trial zinc-rich colostrum and supplementing the The best diagnosis of a mineral defi­ less efficient dietary supply route for zinc. ciency is obtained when specific mineral By reducing the mineralisation of bone (e.g. supplements improve health or productivity Sykes et al. 1979), gastrointestinal parasit­ (Suttle 1994b). However, there is room for ism may reduce the skeletal reserve of considerable improvement in the way that zinc. such responses are sought. Failure to sig­ nificantly improve group performance by a Assessment of Mineral Status given treatment could arise because the mineral deficiency was: (1) irreversible; The influence of 'non-dietary' factors on the (2) not fully reversed; (3) not affecting the mineral status of livestock, whether they be whole group; (4) not the only factor limiting related to infection, upsurge in demand or performance. redistribution of reserves, must affect the Factors that need to be considered in approach to the diagnosiS, anticipation and dose-response trials include: (1) the dele­ prevention of disorders. Relationships terious effect of the deficiency on milk yield between mineral composition of the whole in the dam cannot be overcome by treating diet or of accessible parts of the animal suckling animals; (2) bolus treatments may (plasma, erythrocytes, liver biopsy and rib be regurgitated; (3) flocks and herds are biopsy) and health are bound to be impre­ rarely uniformly affected; (4) there may be cise. more important influences on production than mineral deficiency such as genetic Three-tier assessment system potential, infectious disease, supply of Uncertainties should be recognised by digestible organic matter. To overcome using a three-tier system to classify the such problems, the improved dose­ mineral status of both diets and animals response trial needs: sustained alleviation of with a 'marginal' band to separate the 'defi­ deficiency; removal of as many 'non­ cient' from the 'normal' mineral status (e.g. mineral' constraints on performance as

41 DETECTION AND TREATMENT OF MINERAL NUTRITION PROBLEMS IN GRAZING SHEEP

possible; use of information on prior perfor­ Bang, K.S., Familton, AS. and Sykes, AR.C. mance (Joyce and Brunswick 1975) and 1990. Effects of ostergiasis on copper status subsequent mineral status (by covariance in sheep: a study involving use of copper oxide wire particles. Research in Veterinary analysis) to reduce or interpret within-group Science, 49, 306-14. variability in performance. Careful compari­ Block, E. 1984. Manipulating dietary anions and son of biochemical indices of mineral status cations for pre-partum dairy cows to reduce with improvement in performance will incidence of milk fever. Journal of Dairy justify and extend the three-tier approach to Science, 67, 2939-2949. assessment described above. Bown, M.D., Poppi, D.P. and Sykes, A.R. 1989. The effects of concurrent infection of Trichos­ References trongylus coLubri{ormis and Ostertagia cir­ cumcincta on calcium, phosphorus and Abu Damir, H., Scott, D., Thompson, J.K., magnesium transactions along the digestive Topps, J.H., Buchan, and Pennie, K. 1990. W. tract of lambs. Journal of Comparative The effect of change in blood acid base status Pathology, 101, 11-20. on body composition and mineral retention in Boyne, R. and Arthur, J.E. 1979. Alterations in growing lambs. Animal Production, 51, 527- neutrophil function in selenium deficient 34. cattle. Journal of Comparative Pathology, 89, AFRC (Agricultural and Food Research Council) 151-8. 1991. A reappraisal of the calcium and phos­ Braithwaite, G.D. 1983. Calcium and phos­ phorus requirements of ruminants. Technical phorus requirements of the ewe during preg­ Committee on to Nutrients. Nutri­ nancy and lactation. 1. Calcium. Journal of tion Abstracts and Reviews, 61, 573-612. Agricultural Science, Cambridge, 50, 711 -1993. Energy and protein requirements of ruminants. An advisory manual prepared by 722. the AFRC Technical Committee on Responses Clarke, R.G., Wright, D.F. and Millar, K.R. 1985. to Nutrients. Wallingford, UK, CAB Intema­ A proposed new approach and protocol to tional, 1-8. defining mineral deficiencies using reference ARC (Agricultural Research Council) 1980. The curves. Cobalt deficiency in young is Nutrient Requirements of Ruminant Livestock. used as a model. New Zealand Veterinary Farnham Royal, Commonwealth Agricultural Journal, 32, 1-5. Bureaux. Eales, A, Gilmour, J.S., Barlow, R.M. and Small, Arthur, ...J.R. 1988. Effects of selenium and J. 1982. Causes of hypothermia in 89 lambs. vitamin E status on plasma creatine kinase Veterinary Record, 110, 118-120. activity in calves. Journal of Nutrition, 118, Field, A C. 1981. Some thoughts on dietary 747-755. requirements of macro elements for rumi­ Arthur. J.R. 1993. The biochemical functions of nants. Proceedings of the Nutrition Society, selenium: relationships to thyroid metabolism 40, 267 -272. and antioxidant systems. Annual Report of Field, AC. and Suttle, N.F. 1979. Effect of high Rowett Research Institute, 11-20. potassium and low magnesium intakes on the Arthur, J.R., Nicol, F. and Beckett, G.J. 1991. mineral metabolism of monozygotic twin The roles of selenium in thyroid hormone cows. Journal of Comparative Pathology, 89, metabolism. In: Momcilovic, B. ed., Trace 431-439. Element Metabolism in Man and Animals-7. Field, AC., Suttle, N.F. and Gunn, R.G. 1968. IMI, 7-3 to 7 -6. Seasonal changes in the composition and

42 NOI'I-DIETARY II'IFLUEI'ICES 01'1 THE MII'IERAL REQUlREMEI'ITS OF SHEEP - N.F. SUTTLE

mineral content of the body of hill ewes. Commonwealth Agricultural Bureaux, 549- Journal of Agricultural Science, Cambridge, 551. 71,303-310. Kirchgessner, M. 1993. Homeostasis and home­ Field, AC, Woolliams, J.A, Dingwall, R.A and orhesis in trace element metabolism. In: Anke, Munro, CS. 1984. Animal and dietary varia­ K., Meissner, D. and Mills, C. F., ed., Trace tion in the absorption and metabolism of Element Metabolism in Man and Animals-8 . phosphorus by sheep. Journal of Agricultural Verslag Media Touristik, 4-21 Science, Cambridge, 103,283-291. Masters, D.G. and Moir, R.J. 1983. Effect of zinc Field, AC., Woolliams, J.A. and Woolliams, C. deficiency on the pregnant ewe and develop­ 1986. The effect of breed of sire on the urinary ing foetus. British Journal of Nutrition, 49, excretion of phosphorus and magnesium in 365-372. lambs. Animal Production, 42, 349-354. Matsui, T., Yano, H., Kawabata, T. and Haru­ Gardner, J.AA 1973. Control of serum Mg moto, T. 1994. The effect of suppressing bone levels in sheep. Research in Veterinary resorption on Mg metabolism in sheep (Gvis aries). Comparative Biochemistry and Bio­ Science, 15, 149-157. physiology, 107 A, 233-236. Goff, J.P., Horst, R.L., Mueller, J.K., Miller, G., Michel, A.R. 1985. Sodium in health and disease: Kiess, A and Dowlen, H.H. 1991. Addition of a comparative review with the emphasis on chloride to pre-partal diets high in cations herbivores. Veterinary Record, 116, 653-657. increases 1,25 dihydroxy vitamin D response Michel, A.R., Moss, P., Hill, R., Vincent, I.C and to hypocalcaemia, preventing milk fever. Noakes, DE. 1988. The effect of pregnancy Journal of Dairy Science, 74,3863-3871. and sodium intake on water and electrolyte Grace, N.D. 1983. Amounts and distribution of balance in sheep. British Veterinary Journal, mineral elements associated with fleece-free 144, 147-157. empty body weight gains in the grazing sheep. Morris, J.G. and Peterson, R.G. 1975. Sodium New Zealand Journal of Agricultural requirements of lactating ewes. Journal of Research, 26, 59-70. Nutrition, 105, 595-598. Horst, R.L., Goff, J.P. and Reinhart, T.A. 1990. Phillippo, M., Reid, G.W. and Nevison, I.M. 1994. Advancing age results in reduction of intesti­ Parturient hypocalcaemia in dairy cows: nal and bone 1,25--dihydroxy vitamin D recep­ effects of dietary acidity on plasma mineral tor. Endocrinology, 126, 1063-1057. and calciotropic hormones. Research in Vete­ Jones, D.G. and Suttle, N.F. 1981. Some effects rinary Science, 56, 303-309. of copper deficiency on leucocyte function in Read, M.V.P., Engels, E.AN. and Smith, W.A sheep and c;:attle. Research in Veterinary 1986. Phosphorus and the grazing ruminant: Science, 31, 151-156. 2. The effects of supplementary P on cattle at Joyce, J.P. and Brunswick, I.C.F. 1975. Sodium Glen and Armoedsvlakte. South African supplementation of sheep and cattle fed Journal of Animal Science, 16, 7-12. lucerne in New Zealand. New Zealand Journal Suttle, N.F. 1974. A technique for measuring the of Experimental Agriculture, 3, 299-304. biological availability of copper to sheep. Judson, G.J., Brown, T.H., Beveridge, l. and British Journal of Nutrition, 32, 395-405. Ford, G.E. 1985. Effect of anthelmintic treat­ - 1975. Changes in the availability of dietary ment on trace element and vitamin B 12 status copper to young lambs associated with age of young sheep. In: Mills, C.F., Bremner, I. and and weaning. Journal of Agricultural Science, Chesters J.K., ed., Trace Element Metabolism Cambridge, 84, 255-261. in Man and Animals-5. Farnham Royal, UK, 1981. Effectiveness of orally administered

43 DETECTION AND TREATMENT OF MINERAL NUTRITION PROBLEMS IN GRAZING SHEEP

cupric oxide needles in alleviating hypocu­ Van Mosel, M., van 't Klooster, A. Th., van Mosel, praemia in sheep and cattle. Veterinary F. and van der Kuilen, J. 1993. Effects of Record, 108, 417 -20. reducing dietary [(Na++ K+) - (CI- + SOi-)] 1987. The nutritional requirement for copper on the rate of calcium mobilisation by dairy in animals and man. In: Howell, J. McC., and cows at parturition. Research in Veterinary Gawthorne J.M., ed., Copper in Animals and Science, 54, 1-9. Man, Vol 1. Boca Raton CRC Press, 22-43. Wiener, G., Suttle, N.F., Field, A.C., Herbert, J.G. -1992. Trace element disorders. In: Andrews, and Woolliams, J.A 1978. Breed differences AH., Blowey, R.W., Boyd, H. and Eddy, R.G., in copper metabolism in sheep. Journal of ed., Bovine Medicine: Diseases and Hus­ Agricultural Science, Cambridge, 91, 433- bandry in Cattle. Oxford, Blackwell Scientific 441. Publications, 261-270. Wilson, W.D. and Field, AC. 1983. Absorption -1994a. Seasonal infections and nutritional and secretion of calcium and phosphorus status. Proceedings of the Nutrition Society, from the alimentary tract of lambs infected 53, 545-555. with daily doses of Trichostrongylus colubri­ formis or Ostertagia circumcincta larvae. -1994b. Meeting the copper requirements of Journal of Comparative Pathology, 93, 61- ruminants. In: Gamsworthy, P.C and Cole, 71. D.J.A, ed., Recent Advances in Animal Nutri­ Winter, W.H., Coates, D.B., Hendricksen, R.E., tion. Nottingham, Nottingham University Kerridge, P.c., McLean, R.W. and Miller, c.P. Press 173-187. 1990. Phosphorus and beef production in Suttle, N.F. and Brebner, J. 1995. A putative role northern Australia, 4. The response of cattle to for larval nematode infection in diarrhoeas of fertilizer and supplementary phosphorus. lambs which did not respond to anthelmintic Tropical Grasslands, 24, 170-184. treatment. Veterinary Record, 137, 311-316. Woolliams, J.A., SuttIe, N.F., Wiener, G., Field, Suttle, N.F., Brebner, J., McLean, K. and AC. and Woolliams, C. 1982. The effect of Hoeggel, F.V. 1996. Failure of mineral supple­ breed and sire on the accumulation of copper mentation to avert apparent sodium defi­ in lambs with particular reference to copper ciency in lambs associated with abomasal toxicity. Animal Production, 35, 299-307. parasitism. Animal Science, 62 (in press). Woolliams, c., Suttle, N.F., Woolliams, J.A, Suttie, N.F. and Field, A.C. 1967. Studies on Jones, D.G. and Wiener, G. 1986a. Studies on magnesium in ruminant nutrition, 8. Effect of lambs from lines genetically selected for low increased intakes of potassium and water on and high copper status. 1) Differences in the metabolism of magnesium, phosphorus, mortality. Animal Production, 43, 293-303. sodium, potassium and calcium in sheep. Woolliams, J.A, Woolliams, C., Suttle, N.F., British Journal of Nutrition, 21, 819-831. Jones, D.G. and Wiener, G. 1986b. Studies on Suttie, N.F. and McLean, K. 1995. Anthelmintic lambs from lines genetically selected for low unresponsive diarrhoeas in ewes and hoggs. and high copper status. 2) Incidence of hypo­ Animal Science, 60, 526A. cuprosis on improved hill pasture. Animal Sykes, A.R., Coop, R.L. and Angus, K.W. 1979. Production, 43,304-313. Chronic infection with Trichostrongylus vitri­ Wright, A.J., Mowat, D.N. and Mallard, B.A nus in sheep. Some effects on food utilisation, 1994. Supplemental chromium and bovine skeletal growth and certain serum constitu­ respiratory disease vaccines for stressed ents. Research in Veterinary Science, 26, feeder calves. Canadian Journal of Animal 372-377. Science, 74, 287-295.

44 Diagnosis of Mineral Deficiencies

David I. Paynter

RMB 1413 Warrenbayne, Victoria 3670 Australia

Outline

Soil indicators of mineral status Sampling Analysis Interpretation Dietary indicators of mineral status Sampling Analysis Interpretation Animal indicators of mineral status Sampling Analysis Interpretation References

45 DETECTION AND TREATMENT OF MINERAL NUTRITION PROBLEMS IN GRAZING SHEEP

J\JI ineral deficiencies in sheep often posed as the definitive diagnosis. However, J W Ipresent as part of a multifactorial carefully controlled response trials cannot disease problem. In diagnosing these defi­ always be conducted on-farm, due to the ciencies, it is essential to consider them as seasonal nature of mineral deficiencies and part of an overall differential disease diag­ the time frames required to reach a diagno­ nosis, along with the potential for infectious, sis. Therefore, an approach based on meas­ genetic, metabolic and non-mineral dietary urement of specific indicators of mineral contributions to a disease condition. Clinical nutrition and the likely response to supple­ signs presenting in the animal should be mentation may be more beneficial (Grace considered foremost. These clinical signs 1983; SCA 1990). Using this approach, an should be compared to the well docu­ indicator of mineral nutrition should be rec­ mented clinical effects associated with the ognised for what it represents-a reflection various mineral deficiencies (Underwood of overall nutrition for that mineral. It may 1977). This examination should consider not accurately reflect the actual biochemi­ whether the signs appear to be acute or cal impairment which leads to a specific chronic in form, what tissues are predomi­ disease lesion. nantly affected and the age or class of This is well demonstrated in the case of animal affected. For example, an apparent copper, which is required for activity of a ataxic condition confined to lactating number of enzymes in most tissues. Each mature ewes may suggest possible calcium copper enzyme in each tissue has a different or magnesium deficiency. In contrast, an rate of depletion or repletion with changes in ataxic condition confined to young lambs copper intake. Rates of depletion also vary may indicate copper or selenium defi­ with the mechanism by which a deficiency is ciency. induced, i.e. simple or thiomolybdate, with Where clinical signs are relatively specific, some copper enzymes in some tissues the possibilities in the differential diagnosis being affected by thiomolybdates far more may be greatly simplified. Examples include than others (Paynter 1984). Decreases in white muscle disease associated with sele­ plasma copper concentration reflect nium and/or vitamin E deficiencies, and decreases in plasma caeruloplasmin activ­ goitre associated with iodine deficiency. ity, which in turn reflect decreases in liver Where signs are non-specific (e.g. ill thrift) copper reserves and the capacity of the liver a number of mineral and non-mineral to synthesise this enzyme (Paynter 1986). factors may need to be considered in the Plasma copper is therefore highly correlated differential diagnosis. This includes the with depletion of liver copper reserves, but is presence of subclinical deficiencies, where only indicative of the changes that may be reduced animal production may be tran­ occurring with other copper enzymes in sient and associated with few, if any, spe­ other tissues. cific signs. In assessing mineral status, the terms In determining mineral nutrition of marginal and deficient are often used to dif­ animals, response to treatment is often pro- ferentiate sub-optimal mineral intakes.

46 DIAGNOSIS Of MINERAL DEFIUt:.NCJES 0.1. VAYNItcf~

These terms are defined as follows: soil types and plant species. Few indicators, • deficient-indicates depleted reserves apart from phosphorus, potassium, and associated with impairment of biochemi­ possibly sulfur, fit this category, and even calor physiological processes, and these are restricted to periods when plants responses to treatment are expected; are actively growing. Soil classifications based on type and pH marginal-indicates reduced reserves, may provide limited general information on and production responses to treatment mineral availability. Similarly, associations may be observed. of local soil types with a specific mineral In using these definitions, it should be problem may be useful in estimating the noted that a deficient level of an indicator extent of a problem at a local level. Granite should not be taken to indicate that clinical derived soils and leached sands may be low disease is present. Onset of clinical disease in minerals such as copper and selenium. is often triggered by other dietary or non­ Highly acid soils may have low availability of dietary factors; the mineral deficiency is a the major cations and molybdenum but be predisposing requirement to the clinical high in manganese. In contrast, alkaline disease condition. In a diagnostic sense, an soils may have low availability of manga­ example is white muscle disease and sele­ nese, zinc and cobalt (Grace 1983; Hosking nium nutrition. White muscle disease should et al. 1986) and high availability of molyb­ not be diagnosed solely on the basis of low denum (Leech and Thornton 1987), and are concentrations of blood selenium or glu­ unlikely to produce selenium deficiency tathione peroxidase; elevated plasma crea­ (Reuter 1975). tine kinase activities should be used to determine the presence of significant Sampling muscle damage. For assessment of the major nutrients in In the remainder of the review, the relative relation to pasture requirements, soil cores merits and uses of various indicators in of the top 10 cm soil profile are commonly soils, diets and tissues for determining used. The final sample for each area usually mineral status in sheep are discussed. comprises 15-30 cores, representing each soil type. These samples may be then air Soil Indicators of Mineral Status dried (max. 40°C) prior to subsampling for further analysis (Rayment and Higginson Soil indicators have limited direct applica­ 1992). bility in determining mineral nutrition of grazing animals, their principal use relating Analysis to defining requirements for plant growth (Grace 1983; Hosking et al. 1986). Specific As many of the analytical procedures soil tests are of most use where there is a used for soils are based on extractable high correlation of the soil indicator with the (rather than total) mineral concentrations, mineral supply to the plant, over a range of results are highly method-specific. Rayment

47 DETECTION AND TREATMENT OF MINERAL NUTRITION PROBLEMS IN GRAZING SHEEP and Higginson (1992) have documented minerals and eliminating them from a diffe­ individual standard methods of analysis rential diagnosis in the animal. Where other commonly used for Australian soils. dietary factors may interact and affect availability of a mineral to the animal, Interpretation dietary analysis is important in defining the extent of these interactions and, in some Interpretation of soil results is highly cases, the most appropriate form of treat­ dependent on the analytical method used. ment. However, for all minerals where In general, soil analytical measurements for dietary interactions may occur, a diagnosis macrominerals are calibrated against plant of deficiency should be based, where possi­ responses, rather than any specific animal ble, on animal rather than on dietary meas­ responses, and any extrapolations to urements. animal nutrition are based on animal dietary requirements. Soil measurements of trace Sampling minerals have a generally poor correlation to animal requirements (Hosking et al. All dietary sources, including pastures, 1986). supplements and water, should be accounted for when dietary mineral intakes Dietary Indicators of Mineral are measured. This may not be achievable Status with sheep on free choice diets where selective intakes of dietary components For many minerals, determination of total may occur, particularly where these dietary dietary mineral concentrations provides a components are highly variable in compo­ useful overall indicator of the adequacy of sition and palatability. In these situations, mineral nutrition to the animal (Table 1). pasture samples should be representative Dietary analysis also forms the basis for of those being selected by the animal and understanding the seasonal nature of the area being grazed, and also reflect mineral deficiencies in grazing sheep. and stocking rate. Separation of pasture may be the preferred measure of mineral samples into the main species, e.g. clovers nutrition to the animal where direct animal and grasses, allows the assessment of sea­ indicators are of limited value or where sonal variations in mineral concentrations dietary interferences in availability to the within and between species composing animal are minimal. Examples include pastures, and enables predictions of calcium, sodium, potassium, manganese mineral nutrition to be made between and zinc (SeA 1990). seasons on the basis of pasture sward It should be emphasised that while dietary composition. This is particularly important measurements of these and other minerals where large seasonal species variations may not accurately correlate with their clin­ occur in pasture composition at marginally ical deficiencies, they do form a strong deficient sites. basis for screening for adequacy of these

48 DIAGNOSIS OF MINERAL DEFICIENCIES - D.f. PAYf'lTER

Analysis dietary interactions may occur with magne­ sium and copper availabilities in diets. For Analytical methods used for determining example, dietary sodium, potassium, nitro­ dietary minerals are principally based on the gen and phosphorus have all been impli­ determination of total mineral concentra­ cated in affecting magnesium nutrition tions. A number of methods and instru­ (SCA 1990). Critical values for magnesium ments is available for single or multi­ availabilities from diets and soils have been element assays. All assays should be veri­ proposed that empirically account for at fied by the use of appropriate standard ref­ least some of these interactions (Kemp and erence materials, which are readily available 't Hart 1957; Lewis and Sparrow 1991). For commercially. copper, where the main interferences in uptake are associated with increased dietary Interpretation molybdenum and sulfur concentrations, Minimum dietary mineral requirements critical values for copper availability can be for sheep are shown in Table 1. Note that calculated (Suttle and McLauchlan 1978) these values are approximate only, even for which appear to closely correlate to copper those minerals where availability may not nutrition in the sheep (Givens and Hopkins be affected by other dietary factors. Their 1978; Paynter, unpubl.). principal use should be to determine the Considerable differences may occur in level of adequacy of minerals. When dietary mineral concentrations of different pasture indicators are used to assess mineral nutri­ species. Direct extrapolation of results from tion of animals, the reserves available in the one pasture species to others is not possi­ animal should be considered. Where animal ble. Examples of pasture species mineral reserves are minimal, deficiency may be variations include: the large differences in induced within a few days. Magnesium is an sodium concentrations measured in natro­ example. In contrast, where there are con­ philes (sodium-tolerant plants that include siderable reserves or conservation of nutri­ many perennial grasses) and natrophobes ents by the animal, deficiency may not be (sodium-intolerant plants that include reached for several months. Examples fescue, lucerne, and sorghums) (Smith et al. include calcium, sodium, cobalt and sele­ 1983); the lower magnesium, molybdenum nium (SCA 1990). and sulfur concentrations in many subterra­ For minerals essential for rumen function, nean clover cultivars compared to other particularly sulfur, dietary estimates of clover species (Evans et a!. 1990); and the requirements may be improved by the decreased copper availability in cruciferous inclusion of dietary nitrogen (SCA 1990). species (Merry et al. 1983) and in annual This inclusion is particularly relevant when grasses versus clovers (Paynter 1989). the nitrogen content of the diet is outside Superimposed over all these dietary that seen with green pasture-based diets, as measurements are the variable effects of occurs with senescent pastures and diets soil intake with sheep grazing at pasture supplemented with nitrogen. More complex (Grace 1983). In particular, soil ingestion

49 DETECTION AND TREATMENT OF MINERAL NUTRfTlON PROBLEMS IN GRAZING SHEEP

may be a major source of cobalt and iodine analyses are now available for the majority (SCA 1990). Direct assessment of these of minerals shown to be essential and com­ elements in the animal is therefore recom­ monly affecting nutrition of the sheep. Most mended. of these indicators have been well calibrated against production or clinical responses to Table I. Minimum dietary mineral requirements treatment, over a range of environmental for sheep (dry matter basis). conditions. For many minerals, several dif­ ferent indicators are available for assess­ Mineral Unit Dietary ment of nutrition; each has advantages and requirementa disadvantages, depending on the situation (Tables 2 and 3). Calcium b g/kg 1.5-2.6 Phosphorusb g/kg 1.3-2.5 This review does not cover all these indi­ Magnesium b.c g/kg 1.2 cators extensively. For this, the reader is K/(Ca + Mg) <2.2 referred to reviews by Grace ( 1 983), Potassium b g/kg 5.0 Hosking et al. (1986), Caple and Halpin Sodiumb g/kg 0.7-0.9 (1985) and SCA (1990). Instead, the indi­ Sulfurb g/kg 2.0 cators listed below are those found by this gig Nb 0.08 reviewer to be currently in use for practical b Cobalt mg/kg 0.07 diagnostic purposes for those minerals Copperd mg available Cu/kg 0.24 principally affecting production. For these lodineb mg/kg 0.5 reasons, animal indicators of manganese Ironb mg/kg 40 status are not covered. Blood manganese Manganeseb mg/kg 15-25 Selenium b mg/kg 0.05 concentrations are very low and other Zincb mg/kg 20-30 tissues show relatively small changes with deficiency (Paynter 1987). a Lower values for maintenance. Upper values or single Similarly, while determination of mineral values are for rapidly growing/lactating sheep. concentrations in faeces potentially pro­ b Values derived from SCA (1990). vides an indication of mineral intake from all C Critical ratio derived from Kemp and 't Hart (1957). d Estimated from copper, molybdenum, sulfur dietary sources including soil, and over­ concentrations (Suttle and McLauchlan 1978). comes dietary sampling problems asso­ ciated with selective intakes, final faecal Animal Indicators of Mineral concentrations are dependent on feed Status digestibility and may not account for true availability of minerals from complex Direct animal measurements potentially sources such as soils. These two major vari­ offer the best indicator of mineral nutrition ables alone limit the defining of critical in the sheep, as they account for dietary faecal concentrations as direct measures of selection and the variable uptake and avail­ mineral nutrition in the animal. ability of minerals. Indicators of mineral Several mineral indicators used for sheep nutrition based on tissue or body fluid show a relatively wide range of values in

50 DIAGNOSIS OF MINERAL DEFICIENCIES D.I. PAYNTER

their correlation with dietary uptake. Others sodium and magnesium as possible indica­ have a limited range of application, princi­ tors for sodium and magnesium. Examples pally relating to nutrition below adequacy. of the latter include plasma copper, zinc, Examples of the former include blood sele­ magnesium and phosphate, all of which nium concentrations or glutathione peroxi­ plateau with adequacy due to homeostatic dase activities with selenium nutrition, mechanisms such as urinary thresholds or plasma vitamin B12 with cobalt nutrition, controls on enzyme synthesis. Applicability plasma sulfate with sulfur nutrition, liver of each of the major indicators is shown in copper with copper nutrition and urine Tables 2 and 3.

Table 2. Summary of significant macro-mineral indicators in the sheep.

Indicator Range Applicability

Deficient Marginal Adequate

Calcium plasma Cab mmollL (mg/L) < 1.25 «50) 1.25-2.12 (50-85) 2.12-2.87 (85-1 15) Metabolic defiCiency eye fluid Cab mmollL (mg/L) < 1.0 «40) 1.0-2.5 (40-100) Post mortem urine Cac J.1mollmosmol 1 Single urine samples

Magnesium plasma Mgb mmollL (mg/L) <0.33 «8) 0.33-0.74 (8-18) 0.74-1.44 (18-35) eye fluid Mgd mmollL (mg/L) <0.5 « 12) 0.5-1.44 (I 2-35) Suitable <48 hours post mortem urine Mgc !lmollmosmol 2 Single urine sample

Phosphorus plasma inorganic pb mmol/L (mg/L) < 1.3 «40) 1.3-2.7 (40-85) faecal P mmollkg DM (g/kg DM) <64.5 «2) >64.5 (>2)

Sodium urine Nac !lmollmosmol 10 Single urine sample parotid saliva mmol/L:mmollL <5 5-14 >14 Na/Kc,e

Sulfur plasma inorganic Sb mmollL (mg/L) <0.3 « 10) 0.3-0.8 (10-25) 0.8-1.9 (25-60) a Alternative units with corresponding values are shown in parentheses. b Paynter (unpublished data).

C Caple and Halpin (1985). d Lincoln and Lane (1985). e SCA (1990).

SI DETECTION AND TREATMENT OF MINERAL NUTRITION PROBLEMS IN GRAZING SHEEP

Sampling should be taken from both affected and normal animals. If the sampling is for moni­ Samples taken for analysis must be rep­ toring purposes, the number of sheep to be resentative of the presenting disease or the sampled depends on the expected normal flock. In a disease investigation, samples variance for the indicator being measured.

Table J. Summary of Significant trace mineral indicators in the sheep.

Indicator Unitsa Range Applicability

Deficient Marginal Adequate

Cobalt plasma B12b nmol/L (Jig/L) 0.18 «0.25) 0.18-0.52 (0.25-0.7) >0.52 (>0.7) sheep> 10 weeks old

Copper plasma Cuc Jimol/L (mg/L) <4.7 «0.3) 4.7-904 (0.3-0.6) >904 (>0.6) Dietary Mo <8 mg/kg DM Lambs> I week old plasma caeruloplasminc U/L <5 5--40 >40 Lambs> I week old

red cell SODc.g U/g Hb <200 200--400 >400 liver Cuc J1mol/kg wet (mg/kg wet) <80 «5) 80-240 (5-15) >240 (> 15) Extent of adequacy

Iodine plasma T4 g lamb/eweb.d 2 Lambs <2 weeks old milk Ib.d J1mol/L (J1g/L) <0.6 «80) >0.6 (>80) thyroid/body g/kg >004 <004 Dead lambs weightb.d

Selenium whole blood Seb Jimol/L (Jig/L) <0.25 «20) 0.25-0.76 (20-60) >0.76 (>60) whole blood GSHpxd,g U/g Hb <30 30-50 >50 plasma Seb.e Jimol/L (J1g/L) <0.15 «12) 0.15-0.51 (12--40) >0.51 (>40)

Zinc plasma Znb Jimol/L (mg/L) <6.1 «004) 6.1-9.2 (0.4-0.6) >9.2 (>0.6) a Alternative units with corresponding values are shown in parentheses. b seA (1990).

C Paynter (1986). d Hosking et al. (1986). e Paynter et al. (1993). f Whelan et al. (1994). g SOD =superoxide dismutase. T4 thyroxine. GSHpx = glutathione peroxase.

52 DIAGNOSIS OF MINERAL DEFICIENCIES - DJ PAYNTER

For blood selenium or glutathione peroxi­ storage of samples should also be consid­ dase, the minimum is 5-7 animals (Paynter ered. Haemolysis may interfere with colori­ et al. 1993). A minimum of 10 animals is metric end point assays; the subsequent suggested for blood copper, vitamin 612 hydrolysis of red cell phosphate esters may (Grace 1983) and for urine sodium and increase free phosphate concentrations in magnesium (Caple and Halpin 1985). For plasma. monitoring purposes, samples should pref­ erably be taken at the time of year when Analysis lowest nutrition of a mineral is expected. Prior to sampling, sheep iihould not be Many of the major mineral assays suitable subjected to extended periods of starvation. for assessment of mineral nutrition in sheep This has been shown to affect the concen­ are now well defined analytically, with com­ trations of several mineral indicators includ­ mercial kit methods available for most. In ing plasma vitamin 612 (Millar et al. 1984) addition, commercial quality control mate­ and plasma phosphate (SeA 1990). Age of rials, suitable for use in both internal and the sheep being sampled also may have an external quality assurance programs, are effect. Plasma vitamin 6 12 concentrations now available for most blood, urine and are normally low in preweaned lambs; tissue mineral assays. Analytical methods weaned or adult sheep should be sampled and results should be verified by using these to assess flock cobalt nutrition (Hosking et materials. al. 1986). Similarly, plasma copper and Where there is a high correlation between caeruloplasmin are normally lower in neo­ two indicators in assessing nutrition of a natal lambs than in older lambs or ewes, but mineral, the indicator used is often deter­ not red cell copper superoxide dismutase mined on the basis of suitability of equip­ (Paynter 1986). In the sheep there are also ment and expertise available. The assay of significant differences between serum and glutathione peroxidase activity or total sele­ plasma copper concentrations and caerulo­ nium in whole blood, and caeruloplasmin plasmin activities, as caeruloplasmin is activity or total copper in plasma are exam­ sequestered into the clot during clot forma­ ples. In each case, there is a high correlation tion (Paynter 1982). between indicators (Caple et al. 1980; Contamination associated with sampling Paynter 1986). Each has advantages or dis­ can be a major problem where minerals are advantages in relation to stability, contami­ assayed directly, particularly at trace con­ nation, equipment requirements etc., and centrations. Sample collection tubes and indicators should be chosen which most suit associated processes should be checked to these particular requirements. ensure that contamination is negligible. Haemolysis in samples can be a major Faecal contamination of urines may present source of interference in some colorimetric major errors in urinary magnesium and endpoint assays. This potential interference sodium determinations (CapJe and Halpin should be removed by appropriate sample 1985). Post collection treatment and pretreatment or appropriate sample blank-

53 DETECTION AND TREATMENT OF MINERAL NUTRITION PROBLEMS IN GRAZING SHEEP

ing in the assay. Potential interference in SCA 1990). However, using the correlation vitamin 8 12 assays by inactive analogues of established between glutathione peroxidase vitamin B 12 is not a significant factor in activity and selenium concentrations in sheep plasma. Only minor amounts of ana­ whole blood of sheep (Caple et aL 1980), logues appear to be absorbed and present 0.76 JlmoJjL is similar to that established in the plasma of sheep relative to that independently using glutathione peroxidase measured with cattle (Halpin et al. 1984). as an indicator of selenium nutrition In the determination of mineral concen­ (Paynter et al. 1993). In the practical sense, trations in single urine samples, variations the between- and within-seasonal variations in mineral concentrations associated with in these indicators with sheep grazing at changes in water intake may be greatly pasture overshadow these apparent differ­ reduced by the inclusion of a measure of ences in defining deficient or marginal total urine solute concentration, using either nutrition. osmolarity or specific gravity in the deter­ For several minerals, the phase of defi­ mination (Caple and Halpin 1985). ciency, i.e. depletion or repletion, can be determined at a single sampling time point. Interpretation This determination is possible where indica­ tors for the same mineral have different Summaries of mineral indicators in the turnover rates. For copper, red cell copper sheep and the ranges associated with defi­ or red cell superoxide dismutase provide a cient and marginal nutrition of these miner­ longer term reflection of copper intake than als are shown in Tables 2 and 3. It is plasma copper. Simultaneous measure­ emphasised that the values in these tables ment of both these indicators can be used to are approximate. Correlations and calibra­ determine if an animal is in a depletion, tions of mineral indicators with field treat­ repletion or steady-state phase of copper ment response trials are often nutrition (Paynter 1986). compromised by the large seasonal varia­ A similar approach is possible for deter­ tions apparent with mineral nutrition mining selenium nutrition. Whole blood (Hosking et al. 1986). Few indicators, par­ selenium concentrations and glutathione ticularly in trace minerals, have been exten­ peroxidase activities reflect selenium intake sively calibrated against production from several months previously. In contrast, responses under true steady-state equilib­ plasma selenium concentrations respond rium conditions. more rapidly to selenium intake (SCA 1990; Thus, Whelan et a1. (1994), on the basis Paynter et al. 1993). of their field responses in wool growth in Interpretation of results should always sheep, suggest that critical values for whole reflect the seasonal nature of mineral defi­ blood and plasma selenium concentrations ciencies. For mineral indicators well corre­ may be 0.76 and 0.50 I-lmol/L, respectively, lated with dietary mineral intake over a wide somewhat higher then the values derived in range, the expected mineral nutrition previous reviews (e.g. Hosking et al. 1986; through successive seasons can often be

S4 DIAGNOSIS OF MINERAL DEFICIENCIES - D.I. PAYNTER

broadly predicted. This is not possible for Leech, AF. and Thornton, I. 1987. Trace ele­ indicators with a range of applications ments in soil and pasture herbage of farms largely confined to nutrition below ade­ with bovine hypocupraemia. Journal of Agri­ cultural Science, Cambridge, 108, 591-597. quacy, and interpretation of these indicators should be confined to the period of sam­ Lewis, D.e. and Sparrow, L.A 1991. Implications of soil type, pasture composition and mineral pling only. content of pasture components for the inci­ dence of grass tetany in the south east of References South Australia. Australian Journal of Experi­ mental Agriculture, 31, 609-615. Caple, I.W., Andrewartha, K.A., Edward, S.J.A. Lincoln, S.D. and Lane, V.M. 1985. Postmortem and Halpin, e.G. 1980. An examination of the magnesium concentration in bovine vitreous selenium nutrition of sheep in Victoria. Aus­ humor: comparison with antemortem serum tralian Veterinary Journal, 56, 160-167. magnesium concentration. American Journal Caple, I.W. and Halpin, e.G. 1985. Biochemical of Veterinary Research, 46, 160-162. Assessment of Nutritional status. The Post­ Merry, R.H., Reuter, D.J., Tiller, K.G. and Young, graduate Committee in Veterinary Science, G.L. 1983. Possible contributions of nutritional Australian Dairy Production Course, Univer­ interactions to copper deficiency in ruminants sity of Sydney. Proceedings No. 76,307-337. in South Australia. Australian Journal of Evans, J., Dear, B. and O'Connor, G.E. 1990. Experimental Agriculture and Animal Hus­ Influence of an acid soil on the herbage yield bandry, 23, 24-29. and nodulation of five annual pasture Millar, K.R., Albyt, AT. and Bond, G.e. 1984. legumes. Australian Journal of Experimental Measurement of vitamin B12 in the livers and Agriculture, 30, 55-60. sera of sheep and cattle and an investigation Givens, D.1. and Hopkins, J.R. 1978. The availa­ of factors influencing serum vitamin B12 bility of copper to grazing ruminants in parts levels in sheep. New Zealand Veterinary of north Yorkshire. Journal of Agricultural Journal, 32, 65-70. Science, Cambridge, 91, 13-16. Grace, N.D. 1983. The Mineral Requirements of Paynter, D.I. 1982. Differences between serum Grazing Ruminants. Occasional Publication and plasma ceruloplasmin activities and No. 9, New Zealand Society of Animal Pro­ copper concentrations: investigation of possi­ duction. ble contributing factors. Australian Journal of Biological Science, 35, 353-361. Haipin, e.G., Harris, D.J., Caple, I.W. and Petter­ son, D.S. 1984. The contribution of cobalamin -1984. Copper-containing enzymes in the analogues to plasma vitamin B12 concentra­ sheep: factors affecting their activities and tions in cattle. Research in Veterinary Science, requirements. In: Baker, S.K., Gawthorne, 37,249-251. J.M., Mackintosh, J.B. and Purser, D.B., ed., Hosking, W., Caple, I.W., Halpin, e.G., Brown, Ruminant Physiology: Concepts and Conse­ AJ., Paynter, D.I., Conley, D.N. and North­ quences. Proceedings of a symposium at Uni­ Coombes, P.L. 1986. Trace Elements for Pas­ versity of Western Australia, May 1984, 329- tures and Animals in Victoria. Melbourne, Vic­ 336. torian Government Printing Office. -1986. The diagnosis of copper insufficiency. In: Kemp, A. and 't Hart, M.L. 1957. Grass tetany in Howell, J. Mce. and Gawthorne, J.M., ed., The grazing milking cows. Netherlands Journal of Metabolism of Copper in Man and Animals, Agricultural Science, 5,4-17. Vol. 1. CRC Press, Florida, 101-119.

ss DETECTION AND TREATMENT OF MINERAL /'/(JTRITION PROBLEMS 11'1 GRAZING SHEEP

-1987. Effect of high dietary manganese on South Australia. Agricultural Record, 2, 44- body and wool growth of sheep. In: Wheeler 50. J.L., Pearson, CJ. and Robards, G.E., ed., SCA (Standing Committee on Agriculture) 1990. Temperate Pastures: their Production, Use Feeding Standards for Australian Livestock: and Management. Australian Wool Corpora­ Ruminants. Ruminant Subcommittee. Mel­ tionjCSIRO, Australia, 390-392. bourne, CSIRO. -1989. Differences in mineral concentrations of Smith, a.s., Young, P.W. and O'Connor, M.B. pasture species; effect of season and site. In: 1983. Some effects of topdressing pasture Hirth J. and Bennison, L., ed., The Feed with sodium chloride on plant and animal Quality of Pasture. Proceedings of Pastures nutrition. Proceedings of the New Zealand Specialist Conference, Department of Agricul­ Grasslands Association, 44, 179-185. ture, Victoria, 59-64. Suttle, N.F. and McLauchlan, M. 1978. Predicting Paynter. D./., Halpin, ca. and Caple /'W. 1993. the effects of dietary molybdenum and Selenium nutrition: assessment using glutath­ sulphur on the availability of copper in rumi­ ione peroxidase. Standing Committee on nants. Proceedings of the Nutrition Society, Agriculture and Resource Management, Aus­ 35,22A. tralian Standard Diagnostic Techniques for Underwood, E.J. 1977. Trace Elements in Animal Diseases. Melbourne, CSIRO. Human and Animal Nutrition. New York, Aca­ Rayment, G.E. and Higginson, F.R. 1992. Aus­ demic Press. tralian Laboratory Handbook of Soil and Whelan B.R., Barrow, N.J. and Peter, D.W. 1994. Water Chemical Methods. Melbourne, Inkata Selenium fertilizers for pastures grazed by Press. sheep 11: wool and liveweight responses to Reuter, D.J. 1975. Selenium on soils and plants: selenium. Australian Journal of Agricultural a review in relation to selenium deficiency in Research, 45, 877-887.

56 Trace Element Supplements for Sheep at Pasture

Geoffrey J. Judson

Central Veterinary Laboratories' Primary Industries S.A. 33 Flemington Street Glenside, South Australia 5065 Australia

Outline

Oral supplements Drenches Copper oxide particles Intraruminal pellets Large intraruminal boluses Intraruminal devices of variable geometry Injectable supplements Indirect methods of supplementation Fertilizers and foliar sprays Mineral licks and blocks Water medication Detrimental effects and interactions Concluding comments Acknowledgments References

57 DETECTION AND TREATMENT OF MINERAL NUTRITION PROBLEMS iN GRAZING SHEEP

arious methods are available for sup­ mentation and such responses also may be V plying trace elements to grazing sheep. impaired by the anthelmintic (Suttle et al. A survey of stock owners in South Australia 1988). showed that injections were regarded as the Cobalt drenches are short-acting although most convenient means of administering the animal can store vitamin B12, the physi­ trace elements to grazing animals (Judson ologically active form of cobalt, in the liver. and Taylor 1993). Soil or plant treatments, The major limitation is the poor retention of mineral licks or blocks, drenches and intra­ the cobalt in the rumen to permit its incor­ ruminal pellets are also convenient means poration into the vitamin by the rumen of providing trace elements. microorganisms. For young rapidly growing Once the need for a trace element sup­ sheep, weekly drenches of cobalt were plement has been established (Paynter, this needed to maintain optimum growth rate p'ublication), the choice of treatment will be but larger and less frequent doses of cobalt influenced by a number of factors including were not as effective (Stewart et al. ] 955; the likely duration of the deficiency, addi­ Lee and Marston ] 969). tional management procedures required, Although the liver of sheep can readily the cost of the supplement and whether the store selenium and copper, the maximum pasture may also respond to the trace single oral dose is limited by consideration element. Table 1 gives a summary of the of toxicity. Sodium selenate and sodium common supplements used to correct or selenite are widely used as selenium sup­ prevent trace element deficiencies in sheep. plements and both are equally effective in Figure 1 shows some of the delivery raising blood selenium concentrations when systems available. given orally or subcutaneously, although the latter method is more effective (Meads Oral Supplements et al. ] 980). Most of the selenium in a salt given by mouth is reduced in the rumen to Drenches elemental selenium which is unavailable. Drenches are generally cheaper than The suggested dose of selenium for sheep, other supplements but they are usually based on blood analysis rather than growth short-acting, particularly for elements such rate, is 0.1 mg/kg liveweight and the dura­ as zinc and manganese (Egan 1972) which tion of effect has varied from 0.5-3.0 the animal does not have the capacity to months (Hosking et al. 1986; Tasker 1992). store in physiologically significant quanti­ The variation in estimates of the effective ties. In practice, the inconvenience of fre­ life of the supplement is due in part to the quent treatments can be reduced if the trace severity of the deficiency and to the method element can be given with other supple­ of assessment, whether responses to the ments such as an anthelmintic. However, supplement are measured in plasma or the reliance on infrequent anthelmintic whole blood and the concentration of sele­ drenches as the sole vehicle may result in nium accepted as indicative of adequate variable and transient responses to supple- status (Langlands et al. 1990b).

58 TRACE ELEMENT SUPPLEMENTS FOR SHEEP AT PASTURE - G.J. JUDSON

Figure I. Delivery systems for trace elements. The scale shown is centimetres. Intraruminal pellets

(a) Selenium pellets (lOg) containing 5% (b) Cobalt pellets (lOg) containing 30% by (c) Salt encrusted cobalt pellets recovered by weight elemental selenium in an iron weight cobaltic oxide in an iron from the rumen of sheep. matrix. matrix.

(e) Steel grub screws (lOg) are given orally (f) An applicator used to administer cobalt with selenium or cobalt pellets to and selenium pellets, steel grub screws reduce salt deposition on the pellet. and copper oxide capsules to sheep.

Copper oxide particles

(d) Demonstration of the use of an (g) Copper oxide particles (2.5 g) in a applicator in administering pellets to soluble capsule. The particles are sheep. composed of a mixture of cupric and cuprous oxide coating a copper core.

59 D ETECTION AND TREA TMENT OF M INERA L N UTRITION P ROBLEMS IN G RAZING SHEEP

Figure I. Cont'd

Large intraruminal boluses Injectable supplements

(h) Controlled-release glass boluses (35 g) (i) Sustained-release rumen bolus (80 g) (I) Barium selenate powder suspended in for use in sheep. The bolus contains by for cattle. The bolus is composed of a a viscous carrier (50 mg selenium/mL) weight 13.4% copper. 0.5% cobalt and compressed mixture of copper. cobalt. suitable for subcutaneous injection. 0.3% selenium in a soluble glass selenium. manganese. zinc. iodine and matrix. vitamins A. D and E. The round end of one bolus has been removed to show the 25 g high density weight.

Intraruminal devices of variable geometry

(j) Iodine capsules for use in the rumen of (k) The Laby device developed for the (m) Solution of vitamin B 12 (2 mg/mL) sheep. Regurgitation of the capsule is sustained delivery of substances in the administered subcutaneously to sheep. prevented by arms on each side of rumen of sheep. It consists of a plastic capsule. barrel which contains the substance and a spring loaded plunger. and folded wings that spring outward after dosing to prevent it leaving the rumen.

60 TRACE ELEMENT SUPPLEMENTS FOR SHEEP AT PASTURE - G.J. JUDSOI'I

Oral doses of copper, usually as copper et al. 1991). The effectiveness of the supple­ sulfate, were evaluated in early studies as a ment is due in part to the relative inertness of means of preventing copper deficiency in the copper oxide particles in the reticulo­ sheep (Cunningham 1949; Lee 1950; rumen, the slow clearance of the dose from Dunlop 1951). Copper drenching is not this segment of the gut and the subsequent effective in increasing liver copper stores retention of the dose in the abomasum. since the rapid absorption of significant The response in liver copper to copper quantities of copper is toxic (Howell, this oxide supplement is affected by a number publication). There is little evidence to of factors including the breed of sheep and suggest that drenching with other forms of diet (Suttle 1987), nematode infestation soluble copper is significantly more effec­ (Bang et al. 1990) and physical properties tive than copper sulfate in correcting copper of the particles (Judson et al. 1984, 1991 a). inadequacy in sheep. Merino sheep tolerate single doses of between 16 and 32 g of copper oxide parti­ Copper oxide particles cles without signs of copper toxicity, although British breeds of sheep appear to Dewey (1977) showed that a single oral have a lower tolerance to copper oxide dose of 10 g cupric oxide needles (labora­ needles (Suttle 1987). The suggested doses tory reagent) when given to sheep increased of copper oxide particles for sheep (see liver copper concentrations. The needles Table 1) are based on studies with Merino which were retained in the alimentary tract sheep which show that these doses should for at least one month lodged in the walls of not raise liver copper above the level per­ the abomasum, and in this acidic environ­ mitted for human consumption (Langlands ment copper was readily released and sub­ et al. 1986b). Although the recommended sequently stored in the liver. Copper oxide doses are higher for cupric oxide needles in particles, a cheaper form of the supplement, the United Kingdom (Anon. 1984), these are produced commercially from copper higher doses for the needles do not appear wire. The particles, which are about 3 mm to be warranted for sheep in Australia long, 1 mm in diameter and have a specific (Judson et al. 1985). gravity of about 6.4, are composed of a Recent studies with sheep at pasture (G.J. mixture of cupric and cuprous oxide coating Judson and P.J. Babidge, unpubl.) have a copper core (Judson et al. 1984). Oral shown for wire particles 1.5-12 mm long doses of the particles (Langlands et al. and 0.5-2 mm in diameter that the diameter 1986a) or the needles (Suttle 1987) are an and density of the particle were the most effective means of providing copper to important physical characteristics which sheep. Single oral doses of the particles raise determined their retention in the alimentary liver copper reserves of sheep for 6- 12 tract: retention was unaffected by the length months even when sheep are on diets of of the particle. Particles with a diameter of moderately high molybdenum and sulfur 0.5 mm and a specific gravity of 6.1 or less content (Langlands et al. 1986a; McFarlane were poorly retained.

61 DETECTION AND TREATMENT OF MINERAL NUTRITION PROBLEMS IN GRAZING SHEEP

Table I. Dose rate and duration of effect of supplements used for the prevention and correction of trace element deficiencies in sheep at pasture.

Supplement and suggested dose Duration Comments (dose/animal or kg liveweight) of effecta

Copper

Copper sulfate drench 9 mg Cullamb 2-3 days Risk of toxicity if dose exceeded, not recommended. 10 mg Cu/kg I month Diethylamine cupro-oxyquinoline sulphonate 0.5 mg Cu/kg subcutaneous injection < 2 months Rapidly mobilised from injection site, risk of toxicity if dose exceeded Copper glycinate I mg Cu/kg subcutaneous injection > 6 months Slight tissue reaction at injection site. Copper calcium ethylenediaminetetraacetic acid I mg Cu/kg subcutaneous injection > 6 months As for copper glycinate. Copper methionate 4 mg/kg subcutaneous injection > 6 months Slowly mobilised, low risk of toxicity, tissue reaction at injection site. Copper oxide particles and needles 1.25 g/Iamb oral in soluble capsule 6 months little risk of toxicity. 2.5 g/sheep oral in soluble capsule 6-12 months

Selenium

Sodium selenate or selenite 0.1 mg Se/kg drench 1-3 months Risk of toxicity if dose exceeded, especially if given by injection: 0.1 mg Se/kg subcutaneous injection 2-4 months selenate is the preferred supplement. Barium selenate powder 1.0 mg Se/kg subcutaneous injection > 12 months Low risk of toxicity. persists at injection site, slight tissue reaction. Heavy selenium pellet, 5% w/w selenium I x 109 pellet orally > 12 months Suitable for weaned sheep. I or 2 grub screws given with pe "et may be beneficial.

Cobalt

Cobalt sulfate or chloride drench 7 mg Co/sheep I week Optimum growth rate with weekly drench, monthly drench prevents 250 mg Co/sheep I month clinical signs of deficiency.

Continued on next page.

62 TRACE ELEMENT SUPPLEMENTS FOR SHEEP AT PASTURE - G.J. JUDSON

Table I. Cont'd.

Supplement and suggested dose Duration Comments (dose/animal or kg liveweight) of effecta

Cobalt - cont'd

Vitamin B'2' 2 mg hydroxocobalamin/mL 2 mg/sheep subcutaneous injection 2 months Ensure aqueous preparation injected well under the skin to reduce leakage to skin surface. Heavy cobalt pellet, 30% w/w cobaltic oxide I x 109 pellet orally > 12 months As for selenium pellet.

Iodine

Potassium iodide or iodate drench 200 mg I/ewe 2-3 months Drench given to ewes 2 and I month before lambing. Iodised oil, 475 mg I/mL 475 mg IIsheep subcutaneous injection 2 years Recommended for use in severe iodine deficient areas. Iodine capsule, lA g iodine I capsule orally/sheep > 3 years Commercial product to be released in 1996.

Manganese

Manganese sulfate drench 6 mg Mn/kg I week Approximate dose and duration of effect.

Zinc

Zinc oxide or sulfate drench 3-10 mg Zn/kg I week As for manganese.

Multi-elements

Soluble glass bolus, 1304% Cu, 0.5% Co, 0.15% Se I x 16 g bolus orally to lambs 6 months Approximate effective life of supplement. I x 33 g bolus orally to sheep 8 months a The duration of effect will depend on the severity of the deficiency.

63 DETECTION AND TREATMENT OF MINERAL NUTRITION PROBLEMS IN GRAZING SHEEP

These studies suggest that increasing the pellet was variable, from less than 1 year to specific gravity and mass of the copper almost 8 years (Wilkins and Hamilton 1980; oxide particles by oxidising the surface of 2 Hunter et al. 1981; Langlands et al. 1990a). mm instead of 1 mm copper wire particles The amount of selenium in the pellet is would improve the retention of the particle probably the major factor determining the in the alimentary tract and, presumably, effectiveness of the pellet-increasing the increase the effectiveness of this source of selenium content of the pellet increases its copper. longevity (Donald et al. 1993; Langlands et Oral doses of cupric oxide or cuprous al. 1994). The effective life of a pellet con­ oxide powder to sheep at pasture were taining 15% by weight elemental selenium found to be poorly retained in the alimen­ was about 4 years whereas the life of the tary tract and resulted in a transient increase commercial pellet, containing 5% selenium, in liver copper reserves (Judson et al. was about 2 years (Langlands et al. 1990a). 1989a; Langlands et al. 1989). In these Two pellets containing lower selenium con­ studies the grain size of the powder used centrations were not as effective as a single was usually less than 80 microns. In other pellet containing double the quantity of studies powder of larger grain size (250- selenium (Langlands et al. 1994). The grain 350 microns) was retained in the alimentary size of elemental selenium also influences tract for up to 13 days in penned sheep and the effectiveness of the pellet (Hudson et al. markedly increased the liver copper 1981; Peter et al. 1981 a; Donald et al. reserves (Cavanagh and Judson 1994). It 1993); pellets containing coarse grains of was suggested that the use of the larger elemental selenium were more effective in grains of copper oxide powder may be a releasing biologically active forms of sele­ cheap supplement for preventing seasonal nium than pellets containing fine grains copper deficiencies in sheep. «10 Jlm). Hudson et al. (1981) suggested that the pellet operated as a voltaic cell, the Intraruminal pellets elemental selenium in the presence of iron being reduced to iron selenide with the The continuous supply of cobalt in the release of hydrogen selenide (elemental rumen of sheep provided by a heavy pellet selenium is biologically inert) (Langlands et was devised by Dewey et al. (1958). This al. 1990b). method was also effective in providing a Initial studies showed that the effective life continuous supply of selenium to sheep of the cobalt pellet (10 g pellet containing (Kuchel and Buckley 1969). Early proto­ 60% by weight cobaltic oxide in an iron types of the selenium pellet (10 g pellet matrix) was greater than 5 years (Dewey et containing 5% by weight elemental sele­ at. 1969). In the late 1970s the cobaltic nium in an iron matrix) lasted for at least 4 oxide content of the commercially available years (Hunter et al. 1981). However, studies pellet was reduced from 60 to 30% due to with the commercially prepared selenium the increasing cost of the cobaltic oxide, pellets showed that the effective life of the and this also increased retention by raising

64 TRACE ELEMENT SUPPLEMENTS FOR SHEEP AT PASTURE G.J. JUDSON the specific gravity of the pellet. The effec­ cobalt or selenium, implying that the effec­ tive life of the pellet containing the lower tive life for the zinc pellet will be shorter than cobalt content was found to vary from 1 to the cobalt and selenium pellets. The princi­ 3 years: the source of the cobaltic oxide ple of the copper pellet is based on contact used in the pellet appears to be a major electrolysis, a process which occurs when determinant of the effective life (Judson et one metal is corroded through aqueous al. 1995). The effective life of this pellet in contact with another metal of higher elec­ preventing phalaris staggers, a disorder in tromotive force. Bray (1994) has suggested sheep responsive to cobalt (Lee et al. 1957), this technique may be suitable for long-term is not known. supply of copper and perhaps zinc. Problems of regurgitation and deposition of calcium phosphate salts have been Large intraruminal boluses encountered with heavy pellets (Millar and Andrews 1964). It has been suggested that The density and overall size of a pellet are pellets are more likely to become encrusted probably the most important properties with calcium salts when ruminal pH rises to expected to influence retention in the rumen between 7 and 8 (Owen et al. 1960) or after (Dewey et al. 1958). The heavy intraruminal extended periods of sheep grazing lush pellets have a specific gravity of about 6. pasture growth (Langlands et al. 1990a). For boluses of lower density, retention is Salt deposition can be reduced by the intro­ aided by increasing the size of the bolus; duction of a steel grub screw with the pellet increasing the size is also important if a (Lee and Smith 1976) and in instances of greater release rate of the active constituent severe salt deposition the administration of is required, as is the case with the slow­ a second grub screw may be beneficial release magnesium boluses developed for (Judson et al. 1995). Dewey et al. (1969) use in sheep and cattle (Davey 1968). reported that the abrasive action of the These boluses consist of 86% by weight grinder also increased the release of cobalt magnesium, 12% aluminium and 2% from pellets given to penned sheep. The copper. To improve retention in the reti­ heavy pellet appears to be well retained by culo-rumen, the boluses are weighted with Merino sheep (Lee and Smith 1976) but this iron shot dispersed throughout the matrix of high retention has not always occurred with the bolus. The sheep bolus weighs about 35 other breeds of sheep (Millar and Andrews g and is designed to erode in the rumen to 1964; Poole and Connolly 1967). release the magnesium; the effective life of Other high density pellets investigated the bolus appears to be less than 5 weeks include a copper pellet (Bray 1994) and a (House and Mayland 1976). zinc pellet (Masters and Moir 1980). The Boluses of glass have been developed to zinc pellet, comprising 5 g zinc shot and 5 g carry trace elements. The solubility of the iron filings, released about 10 mg zinc daily glass can be controlled by altering the major for about 7 weeks. The daily release rate for constituents-calcium, phosphorus and zinc is more than 10 times that required for sodium ions. Telfer et al. (1984) reported

65 DETECTION AND TREATMENT OF MINERAL NUTRITION PROBLEMS IN GRAZING SHEEP

that oral dosing of a soluble glass bolus was has been reduced from 0.3 to 0.15%. The an effective means of providing an approxi­ lamb bolus weighs about 16 g and the mately consta nt supply of additional trace sheep bolus 33 g and, according to com­ elements to the grazing animal for many mercial claims, the effective life of each months. The glass bolus was retained in the bolus is 6 and 8 months, respectively. reticule-rumen and dissolved at a controlled Lawson et al. (1989) developed a sus­ rate in the ruminal fluid: the trace elements tained-release rumen bolus for cattle. It is incorporated in the glass matrix were cylindrical with one rounded end and is released as the glass dissolved. A bolus, composed of a compressed mixture of containing by weight 13.4% copper, 0.5% copper, cobalt, selenium, manganese, zinc cobalt and 0.3% selenium, was developed and iodine, and vitamins A, D and E. The for use in sheep and cattle in the United surface, apart from the flat end, is coated Kingdom (Knott et al. 1985). Two sizes of with a polymer resin. Loss of active material bolus were developed for sheep-17 g for occurs from the exposed flat end of the lambs and 35 g for weaned sheep. The bolus in the reticulo-rumen. The coating boluses were effective for up to 6 months in progressively breaks off to maintain a con­ lambs and 12 months in older sheep (Care stant exposed surface area. To improve et al. 1985; Carlos et al. 1985). retention of the bolus a 25 g high-density Because the surface of the bolus dis­ weight was incorporated into the round end solves, coating of the pellet was not of the bolus (Parkins et al. 1994b). The rec­ encountered. The glass boluses (density of ommended dose is two 80 g boluses for about 3) were larger than the intraruminal cattle over 150 kg liveweight. The reported pellets (density about 6) to ensure retention release rate of most of the elements (Hem­ in the reticulo-rumen. Problems encoun­ ingway et al. 1993) is similar to the tered with glass boluses induded surface minimum dietary allowances for young deterioration during packaging and frag­ cattle; the release rate of copper of 138 mentation of the bolus in the rumen mg/day appears excessive for young cattle (Judson et al. 1988; MiIlar et al. 1988). The when on diets of high available copper (SCA bolus was withdrawn from the British 1990). The effective life of the supplement is market in 1986 but has been replaced by a 8 months, although evidence for this has reformulated bolus (S.B. Telfer, pers. only been substantiated for selenium (Allan comm.) prepared by pressing ground glass et aL 1993; Parkins et al. 1994b). An experi­ containing copper and cobalt with sodium mental prototype has been developed for selenate. The bolus is heated to fuse the use in sheep (Parkins et al. 1994a). glass particles together with the sodium sel­ en ate bound into the spaces between the Intraruminal devices of variable glass, and to prevent surface deterioration geometry prior to use the bolus is sealed in foil. The trace element content of the reformulated A range of intraruminal devices (Laby bolus is unaltered except for selenium which 1980; Graham 1989) has been developed

66 TRACE ELEMENT SUPPLEMEf'I7S FOR SHEEP AT PASTURE - G.J. JUDSON

for the controlled delivery of substances in escape. The reservoir is surrounded by a the rumen of sheep and cattle. The release saturated osmotic agent that is contained of the active substance is by diffusion, dis­ within a rigid semi-permeable outer casing. solution or by a galvanic effect. The magne­ As ruminal fluid enters the rigid outer layer, sium bolus is an example of the last the expanding osmotic agent squeezes the process. It consists of two half cylinders of flexible inner reservoir, delivering the sele­ magnesium alloy hinged together with nium at a constant rate. rubber. Following administration the half The Laby device employs a dissolution cylinders open out to prevent regurgitation, process. It consists of a plastic barrel the magnesium being released by electro­ housing tablets of the active constituent lytic action over a period of about 90 days. and a spring loaded plunger. The device is The magnesium bolus is available commer­ fitted with folded wings that spring outward cially for the prevention of magnesium defi­ after oral dosing to prevent it from leaving ciency in cattle. the reticulo-rumen. The barrel is open at The iodine capsule employs a diffusion one end to expose the surface of the tablet process to supply iodine to sheep (Mason to the ruminal fluid. The surface in contact and Laby 1978; ElIis and Coverdale 1982). with the fluid forms a gel and the expulsion Solid iodine, which is contained in a poly­ rate of the gel from the barrel is equal to the ethylene envelope, is in equilibrium with rate of entry of the ruminal fluid to give a iodine vapour which diffuses through the continuous rate of delivery of the active plastic at a constant rate. The plastic offers constituent. The composition of the tablets enough resistance to the diffusion of the can be varied to incorporate inert material vapour to limit its escape to an amount suf­ which permits a break in the delivery of the ficient to meet the iodine needs of sheep for active substance. The Laby capsule has up to 6 years (P. Costigan, pers. comm.); been developed as a faecal marker capsule the maximum duration of effectiveness of a using chromic oxide for estimating feed single injection of iodised poppy seed oil is intake of grazing ruminants (Ellis et al. about 2 years (Statham and Koen 1982). 1982) and for the sustained delivery of an Regurgitation of the capsule is prevented by anthelmintic (Anderson et al. 1980). Small arms on each side of the capsule which amounts of sodium selenate incorporated spring out once in the rumen. This device is in the anthelmintic matrix have been suc­ due for release commercially in the near cessful in preventing selenium inadequacy future. in lambs for at least 26 weeks (Grace et al. The osmotic pump also uses a diffusion 1994). The Laby device has been used process. The pump has been shown to experimentally in sheep for the controlled release physiologically significant quantities delivery of a number of other trace ele­ of selenium in cattle for at least 30 weeks ments including copper, cobalt, manganese (Campbell et al. 1990). The pump consists and zinc at rates sufficient to meet their of a flexible reservoir that contains one hole requirements for 12 weeks (Panggabean et to allow the sodium selenite matrix to al. 1984).

67 DETECTION AND TREATMENT OF MINERAL NUTRITION PROBLEMS IN GRAZING SHEEP

Injectable Supplements Methods used to provide a slow and sus­ tained release of selenium subcutaneously Supplements vary from those that are have included the administration of sodium rapidly mobilised from the injection site to selenate or selenite in a viscous carrier replenish physiological stores to those that (Hidiroglou et al. 1971) or in a soluble glass are constrained by a variety of chemical and pellet (Alien et al. 1981) and of barium se 1- physical methods at the injection site to enate in a viscous carrier (Kuttler et al. provide a slow or sustained-release of the 1961). Barium selenate powder suspended element. Considerable attention has been in a viscous carrier has been developed given to the development of copper prepar­ commercially for use in livestock (Cawley ations which can be given in non-toxic and McPhee 1984). Single subcutaneous amounts to provide long-term protection doses of barium selenate provide a slow, .against deficiency (Alien and Moore 1983; sustained release of selenium in sheep for Alien 1987). A number of the organic com­ 2-4 years (Ovemes et al. 1985; Judson et plexes of copper have been evaluated and al. 1991b). are available for use in sheep: they include The recommended dose of selenium of copper di-ethylamine oxyquinoline sulpho­ 1 mgjkg liveweight is 10 times the dose nate (CuDOS). copper glycinate. copper recommended for sodium selenate or methionate and copper-calcium ethylene selenite, the more soluble forms of sele­ diamine tetraacetic acid (CuCaEDTA). nium. Selenium when given as a single sub­ These complexes differ in the rate the cutaneous dose of 0.5 mgjkg liveweight as copper is translocated from the injection sodium selenate to sheep can result in sele­ site to the liver, and it appears that this rate nium residues in tissues above those rec­ of mobilisation is directly related to the tox­ ommended for human consumption, but icity of the complex and its efficacy in cor­ such an accumulation of selenium residues recting copper deficiency and inversely is unlikely to occur with barium selenate related to the severity of tissue reaction at injections when given at the recommended the injection site (Camargo et al. 1962; dose. except at the injection site (Archer Suttle 1981). Copper methionate is the and Judson 1994a,b). safest complex. CuDOS the most toxic and Significant quantities of vitamin B12 are the other two complexes are intermediate in sold in southern Australia for subcutaneous their toxicity. Sheep appear to tolerate administration to livestock for the correc­ doses up to about 13 mg copper/kg live­ tion and prevention of cobalt deficiency. weight when given as copper methionate The commercial product is a mixture of ([shmael and Howell 1977) but toxicity has hydroxocobalamin (80%) and cyanocobal­ been observed with doses of 0.7 mg amin (20%). A major limitation with this copper/kg when given as CuDOS (Mason et form of therapy is the short duration of al. 1984). The suggested therapeutic doses effect-up to 2 months in young sheep when of these complexes for sheep differ mark­ given at the suggested dose of 1 mg (Hogan edly (see Table 1). et al. 1973; Hannam et al. 1980). The

68 TRACE ELEMENT SUPPLEMENTS FOR SHEEP AT PASTURE - G.J. JUDSON

vitamin is relatively non-toxic but larger humans (Bastrup-Madsen et al. 1983). It is doses are unlikely to increase the effective a cyanocobalamin-tannin complex sus­ life. pended in a sesame oil aluminium­ When given subcutaneously as an monostearate gel. Studies with this product aqueous solution of either 2 mg hydroxo­ have shown that it was no more effective cobalamin or 2 mg cyanocobalamin to than the aqueous preparation of vitamin young sheep, the vitamin was rapidly mob­ B12 in raising the vitamin B12 status of ilised and a significant proportion of the lambs at pasture (Judson et al. 1989b) or in dose excreted in the urine within 6 hours penned sheep fed a cobalt deficient diet (see Figure 2; Judson et al. unpubl.). The (Figure 3; Judson et al. unpubl.). hydroxocobalamin, which is less readily excreted and more effective in raising liver Indirect Methods of vitamin B12 reserves than cyanocobalamin, Supplementation is the preferred analogue (see Figure 3). A depot vitamin B12 was developed for use in Fertilizers and foliar sprays

100 The minimum concentrations (mgjkg dry matter) of trace elements in legume-based ffi[J Cyanocobalamin o Hydroxocobalamin pastures for optimum growth of pasture

80 plots are about 0.04 for cobalt,S for copper, -g o for iodine, 15-20 for manganese, 0 for 1ii selenium and 20-25 for zinc (Reuter and Ux Q) Robinson 1987). The respective minimum ~ 60 o "0 dietary allowances for sheep are 0.11, 5, '5 0.5, 15-20, 0.05 and 20-30 (SeA 1990). -J!. From this comparison it appears that if . ~ 40 ]1 sheep are at risk of copper and zinc defi­ ::J E ciency then pastures may also respond to o::J the trace element supplementation. In such 20 instances the use of trace element fertilizers may be the most economical means of o meeting the needs of both plant and animal. 0.25 1.0 2.0 4.0 14.0 Days after lrealmenl The persistence of trace elements applied to soils can vary markedly and depend on Figure 2. Mean values (with their standard deviations) for the cumulative interactions between soil conditions, the excretion of 57Co in urine, expressed as a percentage of the dose trace element applied and placement of the given, from sheep given subcutaneous injections of 2 mg fertilizer in the soil (Hannam and Reuter cyanocobalamin-57Co (three sheep) or 2 mg hydroxocobalamin_57Co 1987). The residual value of applied zinc (four sheep). can vary from 2 to 10 years on calcareous

69 DETECTION AND TREATMENT OF MINERAL NUTRITION PROBLEMS IN GRAZING SHEEP soils and greater than 10 years on acid soils silage can raise the trace element concen­ (R.J. Hannam, pers. comm.). The residual trations in feed supplements for livestock. value of copper applied to soils can be con­ Selenium topdressing of pasture was first siderable. For example, a copper dressing used in New Zealand in the early 1980s of 2 kg/ha to mineral soils provided ade­ (Watkinson 1994); the maximum permitted quate copper for pasture and sheep pro­ was 109/ha of selenium as sodium sele­ duction for at least 23 years (Hannam et al. nate. Although there was some concern 1982). However, responses in copper con­ about the risk of selenium toxicity to stock, centrations in pasture to copper topdressing Watkinson reported that there had been no appear to plateau at concentrations of cases of toxicity after 10 years of topdress­ about 8-10 mg/kg dry matter (McFarlane ing pasture with sodium selenate granules et al. 1990). Therefore, where copper defi­ mixed with fertilizer. Studies by Whelan and ciency in sheep is induced by excess levels Barrow (1994) have shown that in a medi­ of dietary molybdenum, sulfur or iron, then terranean environment a single application direct supplementation of the animal may be more effective than copper topdressing. 600 Plant analysis for copper and the interfering o Untreated agents is valuable in deciding the most • Cyanocobalamin appropriate means of treatment. 500 1: Hydroxocobalamin 0) In areas where sheep are at risk to cobalt "iii 3: 400 • Depot B12 or manganese deficiency the topdressing of Q5 these elements to soils, as a means of pro­ 3: 0) ~ viding these elements to the animal, is not (5 300 E generally encouraged because the residual c c\; effect of applied cobalt or manganese is aJ usually short and variable due to the ability (jj 200 > of soils to adsorb these elements (Adams et :.::J al. 1969; Reuter et al. 1988). Cobalt misting 100 of the pasture is an alternative means of providing cobalt to the animal. The cobalt is o applied in strips across the grazed site but -20 o 20 40 60 80 100 120 regular applications are required during inclement weather. However, when the Days after treatment cobalt is applied with a wetting agent at a Figure 3. Response in liver vitamin B12 concentrations in untreated sheep and in rate of about 10 g cobalt/ha to leafy pasture sheep given 2 mg vitamin B 12 subcutaneously as cyanocobalamin, it can prevent phalaris staggers and cobalt hydroxocobalamin or depot B12. Mean values are for four sheep, deficiency in sheep for up to 3 months (J.D. except for the cyanocobalamin treatment (three sheep). The least McFarlane, pers. comm.). Foliar sprays significant difference for all comparisons (P = 0.05) was 120. Liver containing one or more trace elements vitamin BI2 concentrations (nmol/kg wet weight) > 200 adequate, applied to herbage before cutting for hay or 100-200 marginal, and < 100 deficient.

70 TRACE ELEMENT SUPPLEMENTS FOR SHEEP AT PASTURE - G.J. JUDSON

of the slow-release fertilizer, barium sele­ limiting production should be identified and nate, at 10 g selenium/ha maintained ade­ supplied instead of the whole suite of ele­ quate blood selenium concentrations in ments. In areas where the trace element sheep for 4 years, whereas a single applica­ deficiency is associated with deficiencies of tion of sodium selenate fertilizer at the same one or more major elements, the use of a rate was effective for 15 months. Selenium complete mineral mix may be the most fertilizer containing a mix of the slow-release appropriate form of supplementation form of selenium as barium selenate and (McDowell, this publication). It is unrealistic quick-release selenium as sodium selenate to expect that the mix will meet the addi­ has been developed. To reduce costs only tional trace element needs of sheep on dry part of the grazed area needs to be top­ pasture in a variety of regions. The limita­ dressed, since sheep do not have to graze tion of using a single mix for different selenium topdressed pasture continuously regions has been shown for copper. The in order to maintain an adequate selenium supplement failed to correct copper inade­ status (Millar and Meads 1987). quacy of sheep on dry pasture of moder­ ately high molybdenum levels (Good et at. Mineral licks and blocks 1992).

Free-access minerals are often conven­ Water medication ient and simple for providing one or more minerals to sheep (McDowell, this publica­ Water medication may prove an effective tion). The ideal supplement is one that is means of providing trace elements to all consumed by all livestock and will provide sheep during dry seasons in areas where all only those elements, in non-toxic amounts, water supplies are controlled. In the more which are insufficient in pasture to meet extensive grazing areas of northern Austra­ the needs of the animal. As it is often lia water medication is a recommended impractical to determine those minerals method of providing phosphorus to cattle which are limiting productivity, mineral during the dry seasons (McCosker and licks and blocks have been produced to Winks 1994). Water medication for provid­ meet the perceived additional needs of ing cobalt or copper to cattle has also been selected minerals for livestock under a successful when using a dispenser to meter range of environmental and management the addition of the trace element to the conditions. water trough (MacPherson 1983). The use White et al. (1992) have developed a of slow-release tablets of copper or cobalt, loose mineral mix containing all the known designed to be placed in water troughs, was essential minerals for sheep on dry pasture found to be ineffective as a means of pro­ in a mediterranean environment. Their viding these elements to cattle (MacPher­ initial findings indicate that the supplement son 1983)-most of the copper released is readily consumed and has increased pro­ from the tablet was retained in the sludge at ductivity. In such instances the element(s) the bottom of the trough. A slow-release

71 DETECTfON AND TREATMENT OF MINERAL NUTRITION PROBLEMS IN GRAZING SHEEP tablet of selenium, however, was shown to 1966). It was suggested that the selenium markedly increase the selenium status of supplement was adversely affecting the cattle, but of concern was the risk of sele­ pregnant ewe during periods of cold stress. nium toxicity if the water selenium concen­ Increased somatic cell counts in milk from tration cannot be maintained at the dairy cows of marginal selenium status intended level (MacPherson 1983). The have been reported when cows were given addition of trace element supplements to a subcutaneous injection of barium selenate water of high salt content, particularly (Whelan et al. 1992). calcium, may result in precipitation of the Interaction between trace element sup­ supplement. plements can reduce the efficacy of the supplement or result in adverse effects on Detrimental Effects and animal health. The efficacy of copper oxide Interactions particles in raising liver copper levels in cattle was shown to be reduced when the Although supplements are given to provide particles were administered with an intra­ physiologically significant quantities of the ruminal selenium pellet (Koh and Judson element in non-toxic amounts to the animal 1987). Intra-muscular injections of selenium there have been instances of adverse effects have been reported to enhance the toxic from supplementation. Depressed live­ effects of oral copper sulfate supplements in weight gains were recorded in lambs given sheep (Hussein et al. 1985). 2 g instead of 1 g copper oxide particles Chronic selenium poisoning was (Langlands et al. 1986b). Depressed live­ observed in dairy cows, previously given weight and fleece weight were observed in two intra-ruminal selenium pellets (30 g young sheep at one of three sites given an pellets containing 10% by weight elemental injection of 12 mg copper as CuDOS selenium in an iron matrix), when given two (Hannam et al. 1982) and reduced tensile high density magnesium pellets (Gill 1993). strength of wool occurred in sheep given It was suggested that an electrochemical injections of 50 mg copper as CuCaEDTA reaction between the two supplements may (Masters and Peter 1990). Depressed have caused a sudden and massive release growth rates due to parenteral injections of of selenium from the pellets-cattle can tol­ copper have also been observed in young erate single oral doses of multiple selenium beef cattle of marginal copper status (Black pellets without signs of selenium toxicity 1982). Clinical signs of copper toxicity were (Judson and McFarlane 1984; Wilson et al. not observed in these studies, although the 1991). An increased release of available possibility of transient sub-clinical copper selenium from high density pellets has been toxicity cannot be discounted. recorded when the selenium pellet was Increased weight loss of ewes associated given to sheep with another heavy pellet with lambing was observed when ewes were containing zinc, zinc/iron, zinc/nickel or given parenteral injections of 3 mg selenium iron (Peter et al. 1981 b). In practice, heavy every 2-3 months (Quarterman et al. pellets of selenium and cobalt are often

72 TRACE ELEMENT SUPPLEMENTS FOR SHEEP AT PASTURE - G.J. JUDSON

given together, yet this combination has period required for the least cost and without little effect on the release of available sele­ risk of undesirable side effects or residues in nium. the animal. There is an ongoing need to monitor the efficacy of the supplement in Concluding Comments preventing trace element disorders. For example, changes in the composition or Our experience in South Australia has source of constituents used in high density shown that even the most vigilant stock intraruminal pellets can significantly reduce owners can become complacent about the effective life of these supplements. Sup­ ensuring livestock productivity is not limited plements for parenteral use, particularly by a mineral deficiency. Part of this compla­ those such as barium selenate which are cency can be attributed to marginal defi­ restrained at the injection site (Archer and ciencies, which are not readily identified, Judson 1994b), should be restricted to sub­ and to the seasonal and year-to-year varia­ cutaneous administration and to sites of the tion in the appearance of a deficiency. This animal not sold for human consumption. variation was shown by Lee (1951) in an Multi-element boluses have considerable area where sheep were at risk to cobalt defi­ appeal to stock owners as a simple means ciency. Sheep were unthrifty as a result of of preventing a number of trace element cobalt deficiency in only 8 of the 13 years of deficiencies. They have the potential to the study, and the severity of the deficiency deliver a number of trace elements, includ­ varied from a marginal depression in growth ing zinc and manganese, at rates to meet rate of the lambs to 100% mortality of the the needs of sheep for many months. lambs. In many instances a marginal trace Although the use of such supplements con­ element deficiency may go undetected yet it taining selenium and copper in areas where may result in up to a 10% depression in sheep are adequate in these elements may growth rate and fleece weight (Judson et at. pose little risk of toxicity there is the risk that 1987). the copper and selenium concentrations in It is important to encourage stock owners the liver of these animals may be above the to adopt recommended methods for the maximum permitted level for human con­ prevention of trace element and mineral sumption (Judson et al. 1988; Langlands et disorders by identifying areas where stock al. 1990a; Masters and Peter 1990). are at risk, by recognising factors contribut­ ing to the disorders, by demonstrating the Acknowledgments cost-benefits of supplementation and making available appropriate diagnostic The author thanks his colleagues at Primary tests for the detection of the disorders. Industries S.A. and Dr Jim Langlands, Armi­ The ideal supplement is one that fits dale for their helpful comments on a draft of easily into management procedures while this paper. providing enough of the element for the

73 DETECTION AND TREATMENT OF MINERAL NUTRITION PROBLEMS IN GRAZING SHEEP

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Element Group. Canterbury, Lincoln College grazing ruminants. I. Degree of oxidation, diet, Printery, 207-213. frequency of dosing and location in the Judson, G.J., Shallow, M. and Ellis. N.J.S. gastro-intestinal tract as factors affecting the 1989b. Evaluation of a depot vitamin B12 ability of oxidized copper wire to promote supplement for lambs. In: McLaren, R.G., hepatic copper storage. Australian Journal of Haynes, R.I.J. and Savage, G.P., ed., Trace Agricultural Research, 37, -179-188. Elements in New Zealand: Environment, - 1986b. Trace element nutrition of grazing Human and Animals. New Zealand Trace ruminants. 11. Hepatic copper storage in young Element Group. Canterbury, Lincoln College and adult sheep and cattle given varying Printery, 225-229. quantities of oxidized copper particles and Judson, G. and Taylor, G. 1993. Detection and other copper supplements. Australian Journal presentation of trace element deficiencies in of Agricultural Research, 37, 189-200. cattle: knowledge, attitudes and practices of 1990a. Selenium supplements for grazing S.A. beef producers. In: Proceedings of the sheep. 2. Effectiveness of intra-ruminal pellets. Sixth J.S. Davies Beef Research Forum. The Animal Feed Science and Technology, 28, University of Adelaide, 1-7. 15-28. Judson, G.J., Woonton, T.R., McFarlane, J.D. Langlands, J.P., Donald, G.E., Bowles. J.E. and and Mitsioulis, A. 1995. Evaluation of cobalt Smith, A.J. 1989. Trace element nutrition of pellets for sheep. Australian Journal of Exper­ grazing ruminants. Ill. Copper oxide powder imental Agriculture, 35, 41-49. as a copper supplement. Australian Journal of Knott, P., Algar, B., Zervas, G. and Telfer, S.B. Agricultural Research, 40. 187-193. 1985. Glass- a medium for providing animals 1990b. Selenium supplements for grazing with supplementary trace elements. In: Mills, sheep. 1. A comparison between soluble salts C.F., Bremner, I. and Chesters, J.K., ed., Trace and other forms of supplement. Animal Feed Elements in Man and Animals-TEMA 5. Science and Technology, 28, 1-13. London, Commonwealth Agricultural - 1994. Selenium supplements for grazing Bureaux, 708-713. sheep. 4. The use of intraruminal pellets con­ Koh, T-S. and Judson, G.J. 1987. Copper and taining elevated quantities of selenium. selenium deficiency in cattle: an evaluation of Animal Feed Science and Technology, 46, methods of oral therapy and an observation of 109-118. a copper-selenium interaction. Veterinary Lawson, D.C., Ritchie, N.S., Hemingway, R.G. Research Communications, 11, 133-148. and Parkins, J.J. 1989. A novel, sustained­ Kuchel, R.E. and Buckley, R.A. 1969. The provi­ release rumen bolus for cattle, containing sion of selenium to sheep by means of heavy trace elements and vitamins. Proceedings of pellets. Australian Journal of Agricultural the Nutrition Society, 48, 89A. Research, 20, 1099-1107. Lee, H.J. 1950. The occurrence and correction Kuttler, K.L., Marble, D.W. and Blincoe, C. 1961. of cobalt and copper deficiency affecting Serum and tissue residues following selenium sheep in South Australia. Australian Veteri­ injections in sheep. American Journal of Vete­ nary Journal, 26, 152-159. rinary Research. 22, 422-428. - 1951. Cobalt and copper deficiencies affecting Laby, R.H. 1980. Modern technology develop­ sheep in South Australia. Part 1. Symptoms ments. Proceedings of the Australian Society and Distribution. Journal of Agriculture, South of Animal Production, 13, 6-10. Australia, 54, 475-490. Langlands, J.P., Bowles, J.E., Donald, G.E. and Lee, H.J., Kuchel, RE., Good, B.F., and Trow­ Smith, A.J. 1986a. Trace element nutrition of bridge, R.F. 1957. The aetiology of phalaris

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staggers in sheep. Ill. The preventive effect of Masters, D.G. and Moir, R.J. 1980. Provision of various oral dose rates of cobalt. Australian zinc to sheep by means of an intraruminal Journal of Agricultural Research, 8, 494-501. pellet. Australian Journal of Experimental Lee, H.J. and Marston, H.R. 1969. The require­ Agriculture and Animal Husbandry, 20, ment for cobalt of sheep grazed on cobalt­ 547-551. deficient pastures. Australian Journal of Agri­ Masters, D.G. and Peter, D.W. 1990. Marginal cultural Research, 20, 905-918. deficiencies of cobalt and selenium in weaner Lee, H.J. and Smith, R. M. 1976. Trace elements sheep: response to supplementation. Austra­ in animal nutrition. In: Lee, H.J., ed., Animal to lian Journal of Experimental Agriculture, 30, Human Nutrition. Achievements and Pros­ 337-341. pects. Melbourne, CSIRO, 1-23. Meads, W.J., Osborn, J. and Grant, A.B. 1980. The effect of single doses of selenium salts on McCosker, T. and Winks, L. 1994. Phosphorus whole blood levels of selenium in ewes on a nutrition of beef cattle in northern Australia. selenium-deficient diet. New Zealand Veteri­ Meat Research Corporation, Department of nary Journal, 28, 20-22. Primary Industries, Queensland, 86 p. Millar, K.R. and Andrews, E.D. 1964. A rnethod McFarlane, J.D., Judson, G.J. and Gouzos, J. of preparing and detecting radioactive cobal­ 1990. Copper deficiency in ruminants in the tic oxide pellets and an assessment of their south east of South Australia. Journal of retention by sheep. New Zealand Veterinary Experimental Agriculture, 30, 187 -193. Journal, 12, 9-12. McFarlane, J.D., Judson, G.J., Turnbull, R.K. Millar, K.R. and Meads, W.J. 1987. Blood sele­ and Kempe, B.R. 1991. An evaluation of nium levels in sheep transferred from sele­ copper-containing soluble glass pellets, nium topdressed to selenium deficient pasture copper oxide particles and injectable copper and vice versa. New Zealand Journal of Agri­ as supplements for cattle and sheep. Austra­ cultural Research, 30, 177-181. lian Journal of Experimental Agriculture, 31, Millar, K.R., Meads, W.J., Albyt, AT., Scahill, 165-174. B.G. and Sheppard, A D. 1988. The retention MacPherson, A. 1983. Oral treatment of trace and efficacy of soluble-glass boluses for pro­ element deficiencies in ruminant livestock. In: viding selenium, cobalt and copper to Suttie, N.F., Gunn, R.G., Alien, W.M., Linklater, New Zealand Veterinary Journal, 36, 11-14. K.A and Wiener, G. ed., Trace Elements in Owen, E.C., Ellis, S.E., Wilson, A.L. and Robert­ Animal Production and Veterinary Practice. son, J. 1960. The occurrence of phosphates British Society of Animal Production, Occa­ of calcium on cobalt oxide 'bullets' adminis­ sional Publication No.7, 93-103. tered to lambs to prevent pining. Proceedings Mason, R.W. and Laby, R. 1978. Prevention of of the Nutrition Society, 19, xxi-xxii. ovine congenital goitre using iodine-releasing Overnes, G., Moksnes, K. and Froslie, A 1985. intraruminal devices: preliminary results. Aus­ Barium selenate: a long-acting selenium prep­ tralian Journal of Experimental Agriculture aration for subcutaneous injection. Acta Vete­ and Animal Husbandry, 18,653-657. rinaria Scandinavica, 26, 164-168. Mason, R.W., McManus, T.J., Henri, D., Middle­ Panggabean, T., Moir, R.J., Purser, D.B. and ton, M. and Sloan, C. 1984. Death in sheep Laby, R. 1984. Multi-element effects in sheep. following dosing with copper diethylamine In: Proceedings of a Symposium on Ruminant oxyquinoline sulphonate as a commercial Physiology. Concepts and Consequences. injectable copper preparation. Australian Vet­ Perth, University of Western Australia, 347- erinary Journal, 61, 38-40. 355.

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Parkins, J.J., Hemingway, R.G., Lawson, D.C. Experimental Agriculture and Animal Hus­ and Ritchie, N.S. 1994a. The effectiveness of bandry, 22, 29-34. copper oxide powder as a component of a SCA (Standing Committee on Agriculture) 1990. sustained-release multi-trace element and Feeding Standards for Australian Livestock: vitamin rumen bolus system for cattle. British Ruminants. Melbourne, CSIRO Publications, Veterinary Journal 156, 547-553. 266 p. Parkins, J.J., Hemingway, R.G., Talty, P.J., Stewart, J., Mitchell, I.W. and Young, F.J. 1955. McSweeney, C. and Crilly, J. 1994b. Intraru­ Cobalt therapy in farm practice with special minal treatment of trace ele,rnent deficiency. reference to Hill farms. The Veterinary Record, Irish Veterinary Journal, 47,253-256. 67,755-757. Peter, D.W., Hunter, R.A and Hudson, D.R. Suttle, N.F. 1981. Comparison between paren­ 1981 a. Optimum Se grain size for selenium terally administered copper complexes of their pellets. In: Howell, J.McC., Gawthorne, J.M. ability to alleviate hypocupraemia in sheep and White, ed., Trace Element Metabo­ c.L., and cattle. The Veterinary Record, 109, 304- lism in Man and Animals-TEMA 4. Canberra, 307. Australian Academy of Science, 218-221. Suttle, N.F. 1987. Safety and effectiveness of Peter, D.W., Mann, AW. and Hunter, R.A 1981b. cupric oxide particles for increasing liver Effect of Zn-containing pellets on selenium copper stores in sheep. Research in Veterinary pellet function. In: Howell, J.McC., Gawthorne, Science, 42,219-223. J.M. and White, c.L., ed., Trace Element Metabolism in Man and Animals-TEMA 4. Suttie, N.F., Brebner, J., Munro, C.S. and Canberra, Australian Academy of Science, Herbert, E. 1988. Towards an optimum oral 199-201. dose of cobalt in anthelmintics in lambs. Pro­ ceedings of the Nutrition Society, 48,87A Poole, D.B.R. and Connolly, J.F. 1967. Some observations on the use of the cobalt heavy Tasker, J.B. 1992. Current options in selenium pellet in sheep. Irish Journal of Agricultural supplementation. In: Trace Elements in Rumi­ Research,6,281-284. nants. Massey University, Veterinary Continu­ ing Education, Publication No. 145, 53-59. Quarterman, J., Mills, C.F. and Dalgarno, A.C. 1966. Strain differences in the response of Telfer, S.B., Zervas, G. and Carlos, G. 1984. Blackface sheep to injections of sodium sele­ Curing or preventing deficiencies in copper, nate. Proceedings of the Nutrition Society, 25, cobalt and selenium in cattle and sheep using xxiii. tracerglass. Canadian Journal of Animal Science, 64, Supplement, 234-235. Reuter, D.J., Alston, AM. and McFarlane, J.D. 1988. Occurrence and correction of manga­ Watkinson, J.H. 1994. Applications of selenium nese deficiency in plants. In: Graham, R.D., to pasture. In: Mineral Nutrition Seminars. Hannam, R.J. and Uren, N.C. ed., Manganese Massey University, Veterinary Continuing in Soils and Plants. Boston, Kluwer Academic Education, Publication No. 157, 125-131. Publishers, 205-224. Whelan, B.R. and Barrow, N.J. 1994. Slow­ Reuter, D.J. and Robinson, J.B., ed. 1987. Plant release selenium fertilizers to correct selenium Analysis: An Interpretation Manual. Mel­ deficiency in grazing sheep in Western Aus­ bourne, Inkata Press, 224 p. tralia. Fertilizer Research, 38, 183-188. Statham, M. and Koen, T.B. 1982. Control of Whelan, N.C., Bruce, R.A, Samson, D.H., Alex­ goitre in lambs by injection of ewes with ander, A.M. and Tasker, J.B. 1992. Evaluation iodised poppy seed oil. Australian Journal of of the production-enhancing effects of

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80 Free-choice Mineral Supplements for Grazing Sheep in Developing Countries

Lee R. McDowell

Department of Animal Science University of Florida Gainesville, Florida 32611 USA

Outline

Factors affecting consumption of mineral mixtures Soil fertility and forage type Season Energy and protein supplements Individual requirements Salt content of drinking water Palatability Availability of fresh minerals Physical form of minerals Biological availability of mineral sources Selecting a free-choice mineral supplement Data and calculations for mineral supplement formulation Evaluation Manufacture of mineral mixes References

81 DETECTION AND TREATMENT OF MINERAL NUTRITION PROBLEMS IN GRAZING SHEEP

or direct supplementation to sheep, the minerals, and would have the advantage of Fobvious advantage of the various not requiring change in the traditional methods of single or limited element sup­ methods of sheep management. An addi­ plementation (e.g., pellets or injections) is tional advantage for a free-choice salt-based the almost certain assurance that each mixture is that the salt can serve as a vehicle animal is receiving the needed element(s), for providing anthelmintics (e.g. phenothia­ compared to the voluntary consumption of zine) or growth promoters. a free-choice (free access) method where There are definite disadvantages to the intakes of individual animals cannot be well free-choice mineral supplementation meth­ controlled. The major disadvantage of od, the major concern being lack of uniform single or limited element administration to consumption by animals. Observations grazing livestock in most parts of the world indicate that some animals may consume is that there are other minerals (e.g., phos­ double their needs while others may eat phorus and sodium) that cannot be admin­ practically none of a supplement. Using the istered in this way (McDowell 1992). In most free-choice method does provide some sheep grazing regions of the world there minerals that are not required, which may also will be deficiencies of sodium and result in higher supplementation costs. phosphorus which must be corrected, and Also, sometimes an injectable mineral may then use of a mixture of salt, calcium, phos­ be preferred to dietary sources to counter­ phorus and trace elements offered free­ act antagonism. In areas of severe molyb­ choice is the probable system of choice. denum toxicity, injections of copper Cost is an additional disadvantage of the compounds are often the preferred method pellets or injections, and elements provided of administration, since the primary site for in a free-choice mixture would generally be copper and molybdenum interaction is the cheaper. gut. In most countries where sheep are raised Intakes offree-choice mineral mixtures by farmers attempt to meet mineral require­ grazing ruminants are highly variable and ments of their flocks through use of free­ not related to mineral requirements choice dietary minerals. Sheep are particu­ (McDowell 1985). Most mammals exhibit larly fond of salt and consume considerably little nutritional wisdom and will select a more per kg of Iiveweight than do cattle palatable but poor quality diet in preference (sheep consume about 5 times more salt to an unpalatable, nutritious diet, even to per kg liveweight than cattle.) This method the point of death. Some researchers have of providing minerals would seem most noted daily consumption of salt-based sup­ appropriate in China. Masters et al. (1995) plements in sheep to be as low as 2-3 noted that many farms in northern China g/animal (Money et al. 1977; Ullrey et al. currently use a salt supplement and 1978) while White et al. (1992) in Australia research indicated that all sheep in northern reported average consumption of 29 g for a China should be given salt regularly. Salt salt-gypsum mixture. A number of re­ provides the vehicle for provision of other searchers report daily mineral consumption

82 FREE-CHOICE MINERAL SUPPLEMENTS FOR GRAZING SHEEP IN DEVELOPING COUNTRIES - L.R. MCDOWELL for sheep of between 10 and 15 g. Fre­ ments that also provide minerals will quently, a proportion of animals in a flock decrease both the need and desire for free­ make little or no use of free-choice mixture; choice minerals. hence, intake of the supplement varies greatly between animals. Ullrey et al. (1978) Individual requirements reported that salt consumption varied widely in ewes (2-14 gjday) and lambs Growth rate, percentage of lamb crop, (1.5-19 gjday). The between-animal varia­ quantity and quality of wool and milk pro­ tion from the Australian study was 22-35 duction influence mineral needs. Added gj day, with variability in intake greatest at requirements of gestation and lactation shorter time periods of less than 6 months increase mineral needs and, thereby, con­ (White et al. 1992). After 6 months the sumption. The higher the level of productiv­ between-sheep variability in intake was esti­ ity, the more important an adequate level of mated to be less than two-fold. mineral intake.

Salt content of drinking water Factors Affecting Consumption of Mineral Mixtures Naturally high salt concentration of drink­ ing water decreases mineral supplement Factors that affect the consumption of intake. Livestock have a natural craving for mineral mixtures have been listed by Cunha salt. However, if that desire is fulfilled from et al. (1964), Cunha (1987) and McDowell drinking water high in salt, grazing livestock (1985, 1992). will consume less or none at all of a free­ choice mineral mixture based on salt. Soil fertility and forage type Where naturally occurring salt content of Usually, the higher the level of soil fertility, water is high, mineral supplements cannot the lower the consumption of minerals. be based on salt and should be reformulated Sheep on low-quality or overgrazed pas­ with other palatability stimulators such as tures consume more mineral supplements. cottonseed meal and molasses. Season Palatability Mineral intake is often greatest during the winter or dry season when forages stop Ruminants have no particular desire for growing, lose green colour and become the majority of minerals, with the exception high in fibre and lignin and low in digestibil­ of common salt. Common salt, because of ity and mineral availability. its palatability, is a valuable 'carrier' of other minerals. If mixtures contain 300-400gjkg Energy and protein supplements salt or more, they are generally consumed The kind and level of protein-energy sup­ on a free-choice basis in sufficient quantities plementation will influence mineral supple­ to supply supplementary needs of other ment intake. Protein and energy supple- minerals. When bonemeal and salt were

83 DETECTION AND TREATMENT OF MINERAL NUTRITION PROBLEMS IN GRAZING SHEEP

mixed together, bonemeal consumption appetite stimulators is important when con­ increased eight-fold (Dew et al. 1954). Many sidering the keeping value of a supplement. reports testify to the beneficial effects of Cornmeal is a good appetite stimulator bonemeal in free-choice supplements. when included in a mineral mixture but is Improperly processed bonemeals can emit more easily fermentable than a protein­ an unpleasant odour, which reduces con­ aceous product such as cottonseed meal. sumption. Also, there is a danger of botu­ The use of 200-400 gjkg salt prevents lism and other disease conditions that can moulding and blowing. be transmitted from inadequately pro­ Mineral feeders will be used more fre­ cessed bone meal. quently by sheep if they are located near Palatability and appetite stimulators such water tanks, shaded loafing areas and areas as cotton seed meal, dried molasses, dried of best grazing. Mineral feeders should be yeast culture and fat help achieve more constructed low enough so that lambs can uniform consumption. Some of these prod­ also consume minerals. They should be ucts not only give the supplement a dust­ located on dry ground accessible for free, moist, and free-flowing character, but checking and servicing throughout the also provide energy and protein. Ingredients year. Mineral boxes should be filled often that increase palatability must be used in and not allowed to get empty. Keeping the moderation, or they will cause overcon­ mineral supply fresh increases its con­ sumption. sumption. In some regions with vast grazing areas, Availability of fresh minerals there are great difficulties in locating feeders Previous diet or access to mineral supple­ so that animals have constant access to ments is a factor affecting short-term con­ minerals. This is a particular problem where sumption of minerals. When sheep have animals graze over large areas with no been deprived of salt for any length of time, central location for drinking water. As with and then get access to it, they may overin­ the water source, the location of the mineral dulge and suffer salt poisoning (treatment­ supplement will affect the movement of the access to water). Under these conditions, sheep in the grazing area and so the siting they will consume 2-20 times the normal of both of these can be used in managing daily quantities of minerals until appetite is the grazing. satisfied. Mineral feeders for sheep should be con­ Physical form of minerals structed so that 1) they cannot be easily Intakes of loose salt-based supplements pushed over, 2) sheep cannot get into them by sheep are substantially higher than and 3) they have a roof to protect the min­ where the same material is offered in a erals from rain. Rainproof mineral feeders compressed form (mineral block). For help increase mineral intake by preventing sheep consuming both loose and block caking, moulding, and blowing away during forms of salt, intake was 7.2 times greater windy weather. The choice of palatability or for the loose form and 2.3 times greater in

84 FREE-CHOICE MINERAL SUPPLEMENTS FOR GRAZING SHEEP IN DEVELOPING COUNTRIES - L.R. McDoWELL a second experiment compared to block Excellent reviews on the significance of forms (Rocks et al. 1982). Likewise, individ­ chelates and complexes for the feed indus­ ual variation in intake from week to week by try have been prepared (Nelson 1988; wethers was considerably less among Spears et al. 1991). Spears et al. (1991) groups offered loose vs block salt mixtures; concluded that the use of certain organic a coefficient of variation of 58% for a loose trace mineral complexes or cheJates in salt mix and 115% for a salt block. Apart ruminant diets has increased performance from a greater uniformity in intake, the use (growth and milk production), carcass of loose instead of compressed salt has a quality and immune responses, and substantial advantage in cost per unit. decreased somatic cell counts in milk com­ Mineral blocks can be developed on the pared with animals fed inorganic forms of basis of degree of hardness to take into the mineral. Trace minerals sequestered as consideration rainfall, humidity and other amino acid or polysaccharide complexes environmental conditions. Rain will dissolve have the highest biological availability and too soft a block causing mineral losses, and also have a higher stability and solubility. yet livestock experience difficulty consum­ These mineral forms also have a lack of ing enough of a hard block to fulfil mineral interaction with vitamins and other ions and requirements. If the animals remain only a are effective at low levels. In cases where limited time in the vicinity of mineral blocks, there is high dietary molybdenum, copper in then excessive block hardness will result in chelated form would have an advantage reduced mineral consumption. Providing a over an inorganic form as it may escape the supplement in block form has the advan­ complexing that occurs in the digestive tages of convenience and much greater system between copper, molybdenum and resistance to rain and dew. Also, the control sulfur (Nelson 1988). of excessive intakes by the use of blocks Some studies have shown no benefit from may be a significant advantage. chelated and complexed minerals, but most have shown positive responses when com­ Biological Availability of Mineral pared to inorganic sources. Spears (1989) Sources showed that zinc-deficient lambs retained zinc from zinc-methionine better than from The bioavailability and percentage of zinc oxide. Zinc in the form of zinc-lysine mineral elements in some inorganic sources fed to sheep resulted in the highest levels of commonly used in mineral supplements are metallothionein in liver, pancreas and shown in Table 1. These variations in bio­ kidney compared to other zinc sources, availability of sources must be taken into thus indicating a more bioavailable source consideration when evaluating or formulat­ of zinc (Rojas et al. 1995). Dietary require­ ing a mineral supplement. Calculations are ments for minerals may be greatly reduced required to account for both the amount of by the addition of chelating agents to animal element in mineral salts as well as bioavail­ diets, but cost to benefit relationships need ability. to be established.

85 DETECTION AND TREATMENT OF MINERAL NUTRITION PROBLEMS IN GRAZING SHEEP

Table I. Percentage of mineral element and relative bioavailability.a

Element Source compound Element in Sio-availability compound (%)

Calcium Steamed bonemeal 29.0 (23-37) High Defluorinated rock phosphate 29.2 (19.9-35.7) Intermediate Calcium carbonate 40.0 Intermediate Soft phosphate 18.0 Low Ground limestone 38.5 Intermediate Dolomitic limestone 22.3 Intermediate Monocalcium phosphate 16.2 High Tricalcium phosphate 31.0-34.0 Dicalcium phosphate 23.2 High Hay sources 23.3 Low

Cobalt Cobalt carbonate 46.0-55.0 - b Cobalt sulfate 21.0 - b Cobalt chloride 24.7 - b

Copper Cupric sulfate 25.0 High Cupric carbonate 53.0 Intermediate Cupric chloride 37.2 High Cupric oxide 80.0 Low Cupric nitrate 33.9 Intermediate

Iodine Calcium iodate 63.5 High Ethylenediamine dihydroiodide 80.0 HighC Potassium iodide, stabilised 69.0 High Cuprous iodide 66.6 High

Iron Iron oxide 46.0-60.0 Unavailable Ferrous carbonate 36.0-42.0 Lowd Ferrous sulfate 20.0-30.0 High

Magnesium Magnesium carbonate 21.0-28.0 High Magnesium chloride 12.0 High Magnesium oxide 54.0-60.0 High Magnesium sulfate 9.8-17.0 High Potassium and magnesium sulfate I 1.0 High

Continued on next page.

86 FREE-CHOICE MINERAL SUPPLEMENTS FOR GRAZING SHEEP IN DEVELOPING COUNTRIES - L.R. McDoWELL

Table I. Cont'd.

Element Source compound Element in Bio-availability compound (%)

Manganese Manganous sulfate 27.0 High Manganous oxide 52.0-62.0 High

Phosphorus Defluorinated rbck phosphate 13.1 (S.7-21.0) Intermediate Calcium phosphate IS.6-21.0 High Dicalcium phosphate IS.5 Intermediate Tricalcium phosphate 18.0 Phosphoric acid 23.0-25.0 High Sodium phosphate 21.0-25.0 High Potassium phosphate 22.8 Soft phosphate 9.0 Low Steamed bonemeal 12.6 (8-18) High

Potassium Potassium chloride 50.0 High Potassium sulfate 41.0 High Potassium and magnesium sulfate IS.O High

Selenium Sodium selenate 40.0 High Sodium selenite 45.6 High

Sulfur Calcium sulfate (gypsum) 12.0-20.1 Low Potassium sulfate 2S.0 High Potassium and magnesium sulfate 22.0 High Sodium sulfate 10.0 Intermediate Anhydrous sodium sulfate 22.0 Sulfur, flowers of 96.0 Low

Zinc Zinc carbonate 52.0 High Zinc chloride 4S.0 Intermediate Zinc sulfate 22.0-36.0 High Zinc oxide 46.0-73.0 High a From Ellis et al. (1988). b Critical tests not done. but source effective.

C Some liberation of free iodine when mixed with trace elements. d Some samples are fairly high in availability-but not as available as ferrous sulfate.

87 DETECTION AND TREATMENT OF MINERAL NUTRITION PROBLEMS IN GRAZING SHEEP

Selecting a Free-choice Mineral level falls below normal (5-8 mg/kg) or the Supplement dietary sulfur level is high (4 mg/kg), molybdenum intake as low as 1-2 mg/kg Though it has been found that grazing live­ may prove toxic. Lactating ewes require stock do not balance their mineral needs 14-17 mg/kg copper when dietary molyb­ perfectly when consuming a free-choice denum is greater than 3 mg/kg. but only mixture, there is often no other practical 7 -8 mg/kg when dietary molybdenum is way of supplying mineral needs under less than 1 mg/kg (Suttle 1983). Thus, the grazing conditions. As a low cost insurance exact level of copper to use in counteracting to provide adequate mineral nutrition, a molybdenum or sulfur antagonism is a modified 'complete' mineral supplement complex problem and should be worked out should be available free-choice to grazing for each area. sheep. A 'complete' mineral mixture usually Table 2 lists characteristics of a 'good' includes salt, a low fluoride-phosphorus (complete or 'shotgun') mineral mix for source, calcium, cobalt, copper, iodine, and sheep. A number of 'authorities' feel there is zinc. Selenium could be included as many no justification for the use of 'shotgun' free­ sheep-grazing regions are selenium defi­ choice mineral mixtures that are designed cient, however, selenosis is also a problem to cover a wide range of environments and in some areas so caution is necessary. feeding regimens and that contain a margin Often sulfur should be included, being more of safety as an insurance against deficiency. important for sheep than cattle. Additional These people feel that 'shotgun' mixtures elements which may be required include are economically wasteful and can also be magnesium, potassium and manganese. harmful. This viewpoint is valid for devel­ Most frequently, iron is not required, with oped countries which have access to ana­ grazing sheep often consuming excesses. lytical laboratories which can easily The modified 'complete' mineral mixture determine mineral status for ruminants. needs to be flexible and readily modified as However, this author believes that in devel­ new information suggests different needs or oping countries or for countries with vast possible excesses. extensive grazing regions, 'shotgun' mix­ Calcium, copper, or selenium, when in tures have been highly successful in excess, can be more detrimental to rumi­ improving ruminant productivity. There is nant production than any benefit derived by little danger of toxicity or excessive cost in providing a mineral supplement. Copper relation to the high probability of increased requirements are greatly influenced by production rates for sheep from administer­ dietary concentrations of molybdenum and ing a complete 'shotgun' free-choice sulfur. With sheep, great care has to be mineral mixture following the guidelines in taken to avoid over-supply of copper Table 2. because of the extreme sensitivity of this Copper, selenium, iron and fluorine would species and even breed differences to be the minerals of most concern for toxicity copper toxicity. When the dietary copper to sheep. Even without mineral analyses,

88 FREE-CHOICE MINERAL SUPPLEMENTS FOR GRAZING SHEEP IN DEVELOPING COUNTRIES - L.R. MCDOWELL

the likelihood of toxicities of copper and conclusion, it is best to formulate free­ selenium in specific regions would be sus­ choice mixtures on the basis of analyses or pected (e.g. clinical signs and high soil pH). other available data. However, when no Iron should be avoided in complete mineral information on mineral status is known for mixtures unless evidence suggests other­ a given region, a free-choice complete wise, and safe sources of phosphorus prin­ ('shotgun') mineral supplement is definitely cipally used to avoid fluorine toxicity. In warranted.

Table 2. Characteristics of a 'good' semi-complete free-choice sheep supplement.

An acceptable complete sheep mineral supplement should be as follows:

I. Contains a minimum of 3-5% total phosphorus. In areas where forages are consistently lower than 0.20% phosphorus, mineral supplements in the 5-7% phosphorus range are preferred.

2. Has a calcium:phosphorus ratio not substantially over 2: I.

3. Provides a significant proportion (e.g., about 50%) of the trace mineral requirements for cobalt, copper, iodine, and zinc.a In known trace-mineral-deficient regions. 100% of specific trace elements should be provided.

4. Sulfur should be provided if forages are consistently lower than 1.5 g/kg sulfur and/or if urea is fed. Due to wool growth, the nitrogen:sulfur ratio should not exceed 10: I.

5. Magnesium and potassium would only be provided when a need is shown.

6. Includes high-quality mineral salts that provide the best biologically available forms of each mineral element, and avoidance or minimal inclusion of mineral salts containing toxic elements. As an example. phosphates containing high fluorine should be either :lvoided or formulated so that breeding sheep would receive no more than 30-50 mg/kg fluorine in the total diet. Fertilizer or untreated phosphates could be used to a limited extent for finishing sheep or in combination with safe sources.

7. Is sufficiently palatable to allow adequate consumption in relation to requirements.

8. Is backed by a reputable manufacturer with quality control guarantees as to accuracy of mineral-supplement label.

9. Has an acceptable particle size that will allow adequate mixing without smaller size particles settling out.

10. Is formulated for the area involved, the level of animal productivity, the environment (temperature, humidity. etc.) in which it will be fed, and is as economical as possible in providing the mineral elements used. a For most regions it would be appropriate to include selenium. unless toxicity problems have been observed. Iron may be included in temperate region mixtures but often both iron and manganese can be eliminated for acid soil regions. In certain areas where parasitism is a problem iron supplementation may be beneficial.

89 DETECTION AND TREATMENT OF MINERAL NUTRITION PROBLEMS IN GRAZING SHEEP

An oral magnesium supplement is of been used to obtain optimal magnesium value only during seasonal occurrences of intakes. For special tetany-preventing mix­ grass tetany (Allcroft 1961). Outbreak of tures, high levels of magnesium are tetany occurs most frequently in nursing required (e.g. 100-200 g magnesium/kg). ewes shortly after they are turned out to pasture in the spring, with the highest inci­ Data and Calculations for dence in the 4-5 weeks following lambing. Mineral Supplement Unfortunately, many commercial magne­ Formulation sium-containing, free-choice mineral sup­ plements are often of little value for sheep To evaluate a free-choice mineral supple­ because (1) they contain inadequate ment, one needs an approximation of: amounts of magnesium to protect against 1) sheep requirements for the essential tetany during susceptible periods, and (2) minerals, which include the age of the provision of such supplements to normal animals involved, stage of current produc­ animals during nonsusceptible periods is tion or reproduction cycle, and intended useless as a prophylactic measure, since purpose for which the animals are being fed; additional magnesium will not provide a 2) relative biological availability of the min­ depot of readily available magnesium for erals in the sources from which they will be emergency use. Some producers feed mag­ provided; 3) approximate daily intake per nesium supplements about a month before head of the mineral mixture and total dry the magnesium tetany season, to decrease matter that is anticipated for the target the amount of magnesium needed daily animals; and 4) concentration of the essen­ during the susceptible period. Various com­ tial minerals in the free-choice mixture. binations of magnesium oxide with salt, The calculations for free-choice mineral protein supplements, molasses, other con­ supplement evaluations are shown below. centrate ingredients, and other feeds have

Sample calculation for free-choice mineral supplement evaluation

element in mineral mixture (g/g) x daily intake of mineral mix (g) element from mineral ------xl00 mixture expressed as total daily dry matter intake (g) percent of the diet. If, for example, copper in mineral mixture 0.0008 gig Daily intake of mineral mixture (g) 15 Total daily intake of dry matter (g) 1800 then: 0.0008 x 15 x 100 = 0.00066% or 6.6 mg/kg 1800

If 8 mg/kg is considered the allowance, then 82.5% of the copper requirement would thus be supplied by this mixture.

90 FREE-CHOICE MINERAL SUPPLEMENTS FOR GRAZING SHEEP IN DEVELOPING COUNTRIES - L.R. McDoWELL

Table 3 illustrates the estimated trace 1) insufficient chemical analyses and bio­ mineral requirements and percentages of logical data to determine which minerals are each element required in a sheep mineral required and in what quantities; 2) lack of mixture to meet 25, 50 or 100% of the mineral consumption data needed for for­ requirements. These figures are based on mulating supplements; 3) inaccurate and/or an estimated daily mineral consumption of unreliable information on mineral ingredient 15 g. With less consumption, the mineral labels; 4) supplements that contain inade­ supplement should contain a higher per­ quate amounts or imbalances; 5) standar­ centage of each mineral. Likewise, a lower dised mineral mixtures that are inflexible for intake of dry matter would reduce the per­ diverse ecological regions (e.g., supple­ centage of minerals required in the mixture. ments containing selenium distributed in a Each producer should determine mineral selenium toxic region); 6) farmers not sup­ consumption for his flock and change plying mixtures as recommended by the products if higher consumption rates are manufacturer (e.g., mineral mixtures diluted required (e.g., increase the cottonseed meal 10: 1 and 100: 1 with additional salt; 7) from 5 to 10%). farmers not keeping their animals continu­ ously supplied with minerals; and 8) difficul­ Evaluation ties involved with transportation, storage, and cost of mineral supplements. Many of Problems concerned with mineral supple­ these problems are more related to develop­ mentation programs in diverse world ins regions, as in more developed countries regions (McDowell et al. 1993) include: there is better quality control of products.

Table 3. Percentage of trace minerals required in an adequate trace mineral supplement for sheep.a

Element Requirementb Percent in mixture for: (mg/kg) 25% 50% 100%

Cobalt 0.1 0.0004 0.0007 0.0014 Copper 8 0.024 0.048 0.095 Iodine 0.8 0.003 0.005 0.01 Manganese 25 0.075 0.15 0.3 Zinc 25 0.075 0.15 0.3 Iron 40 0.12 0.24 0.48 Selenium 0.2 0.0007 0.0013 0.0026 a This assumes an average consumption of 15 g/day of mineral mixture and 1.8 kg/day of total dry feed per animal. As an example. this could be equivalent to the needs of a 70 kg ewe during the last 4 weeks of gestation or last 4-6 weeks lactating suckling Singles. b NRC (1985).

91 DETECT/ON AND TREATMENT OF MINERAL NUTRITION PROBLEMS IN GRAZING SHEEP

Responsible firms that manufacture and nants and monogastric animals with the sell high-quality mineral supplements same mixture. This unbalanced mineral provide a great service to individual mixture, which is extremely high in calcium farmers. However, there are companies that (294 g/kg) and low in phosphorus (18 are responsible for exaggerated claims of g/kg), would likely be more detrimental to advertising and some that produce inferior grazing sheep than having no access to products that are of little value-or worse, supplemental minerals, and may actually those likely to be of detriment to animal contribute to a phosphorus deficiency. production. Table 4 provides an example of an inferior mineral mixture available in Latin Manufacture of mineral mixes America. This particular mineral supple­ ment is recommended for cattle, sheep, Mineral elements exist in many chemical pigs, and chickens. It is impossible to ade­ forms including sulfates, carbonates, chlo­ quately meet requirements of both rumi- rides, oxides and organic forms (e.g., amino

Table 4. An inferior mineral mixture available for sheep in Latin America.a,b,c

Element Mineral Amount in Allowance Proportion of dietary mixture provided from allowance provided allowance mineral mixture from mineral mixture (%)

Sodium chloride 5 g/kg 200 g/kg 1.7 g/kg 34.0 Calcium 4 g/kg 294 g/kg 2.5 g/kg 62.5 Phosphorus 2 g/kg 18 g/kg 0.15 g/kg 7.5 Magnesium 1.5 g/kg 32 g/kg 0.27 g/kg 17.8 Iron 40 mg/kg 8800 mg/kg 73.3 mg/kg 183.3 Zinc 25 mg/kg 200 mg/kg 0.16 mg/kg 0.6 Cobalt 0.1 mg/kg 20 mg/kg 0.16 mg/kg 60.0 Iodine 0.8 mg/kg 10 mg/kg 0.08 mg/kg 10.0 Copper 8.0 mg/kg 150 mg/kg 0.125 mg/kg 1.6 Manganese 25 mg/kg 750 mg/kg 0.62 mg/kg 2.5 Selenium 0.2 mg/kg 5 mg/kg 0.041 mg/kg 20.5 a Modified for sheep: from McDowell et al. (1993). b Mineral mixture is recommended for cattle. sheep, pigs, and chickens. It is assumed that mineral consumption will average approximately 0.5% of the total dietary intake. This is based on an estimated intake of 15 g of mineral mixture for sheep and 1.8 kg of total dry feed per head daily.

C Criticisms of mineral mixture are as follows: I) mixture extremely low in phosphorus and exceptionally high in calcium (the calcium:phosphorus ratio is 16.4: I); 2) the supplement does not provide a significant proportion (Le. 50%) of the trace mineral requirements of copper. iodine. zinc. manganese and selenium; 3) the majority of the iron is from ferric oxide. an unavailable form of this element; 4) since this diet contains 294 g/kg calcium and only 200 g/kg salt (NaCI). it is likely to be of low palatability.

92 FREE-CHOICE MINERAL SUPPLEMENTS FOR GRAZING SHEEP IN DEVELOPING COUNTRIES - L.R. McDoWELL acid complexes}. The form chosen for use Masters, D.G .• Yu, S.X., Wang, Z.S., Lu, D.X. Wu, should depend on its biological value, cost, L.H., Ren, J.K., Li, G.H. and Purser, D.B. 1995. availability in the area, its stability and effect Consequences of mineral deficiencies in sheep in northern China. In: Anderson, N., Peter, in the type of diet used and other functions. D.W., Masters, D.G. and Petch, D.A., ed., Pro­ It is important to know what combinations duction of Fine Wool in Northern China: Effect of mineral salts to mix together to avoid their of Nutrition and Helminth Infections. Canberra, reacting with each other and causing Australian Centre for International Agricultural adverse effects in a mineral mixture (Cunha Research, Technical Report No. 32,45-50. 1987). Both loose and block mineral forms McDowell, L.R. 1985. Nutrition of Grazing Rumi­ also need to be stored and fed under a wide nants in Warm Climates. New York, Academic range of weather conditions and under Press, 443 p. - 1992. Minerals in Animal and Human Nutri­ varying levels of rainfall or snow. A particu­ tion. San Diego, California, Academic Press, lar expertise is required to produce mineral 524 p. blocks; if the block is too hard, consumption McDowell, L.R., Conrad, J.H. and Hembry, F.G. will be reduced, if not hard enough, the 1993. Minerals for Grazing Ruminants in T rop­ product will crumble. The user of mineral ical Regions, 2nd ed. Gainesville, Florida, Uni­ supplements must rely on the reputation versity of Florida, 78 p. and integrity of the mineral feed manufac­ Money, D.F.L., Meads, W.J. and Morrison, L. turer. Safe, biologically available and palat­ 1977. Selenised compressed salt blocks for able forms of the minerals, at a fair price, selenium-deficient sheep. New Zealand Veteri­ nary Journal, 34, 81-84. allow both the user and manufacturer to Nelson, J. 1988. Review of trace mineral chelates realise a profit from their use. and complexes available to the feed industry. Western Nutrition Conference. Winnipeg, References Manitoba, Canada, 19 p. Allcroft, R. 1961. The use and misuse of mineral NRC 1985. Nutrient requirements of domestic supplements. Veterinary Record, 73, 1255- animals. Nutrient Requirements of Sheep (5th 1266. ed.), Washington, D.e. National Academy of Cunha, T.J. 1987. Salt and Trace Minerals. Alex­ Sciences-National Research Council, 99 p. andria, Virginia, Salt Institute, 42 p. Rocks, R.L., Wheeler, J.L. and Hedges, D.A. Cunha. T.J., Shirley. R.L.. Chapman, Jr. H.L.. 1982. Labelled waters of crystallization in Ammerman. e.B., Davis. G.K., Kirk. W.G. and gypsum to measure the intake by sheep of J.F. 1964. Minerals for Beef Cattle in loose and compressed mineral supplements. Florida. Florida Agriculture Experiment Australian Journal of Experimental Agricul­ Station Bulletin. 683, Gainesville. 60 p. ture and Animal Husbandry, 22, 35-42. Dew, M.I., Stoddard, G.E. and Bateman, G.O. Rojas, L.X., McDowell, L.R., Cousins, R.J., Martin, 1954. Phosphorus supplements made more F.G., Wilkinson, N.S., Johnson, A.B. and palatable with salt. Utah Farm and Home Velasquez, J.B. 1995. Relative bioavailability Science, 15, 36. of two organic and two inorganic zinc sources Ellis, G.L., McDowell, L.R. and Conrad, J.H. fed to sheep. Journal of Animal Science, 73, 1988. Evaluation of mineral supplements for 1202-1207. grazing cattle in tropical areas. Nutrition J.W. 1989. Zinc methionine for rumi­ Reports International, 38,1137 -1147. nants: relative bioavailability of zinc in lambs

93 DETECTION AND TREATMENT OF MINERAL NUTRITION PROBLEMS IN GRAZING SHEEP

and effects on growth and performance of (Jllrey. D.E., Light, M.R., Brady, P.S., Whetter, growing heifers. Journal of Animal Science, P.A., Tilton, J.E., Henneman, H.A. and Magee, 67,835-843. W.T. 1978. Selenium supplements in salt for Spears, J.W., Kegley, E.B. and Ward, J.D. 199]. sheep. Journal of Animal Science, 46, 1515- Bioavailability of organic, inorganic trace min­ 1521. erals explored. Feedstuffs, 27, 12-20. White, CL., Masters, D.G., Peter, D.W., Purser, Suttle, N.F. ] 983. The nutritional basis for trace D.B., Roe, S.P. and Barnes, M.J. 1992. A element deficiencies in ruminant livestock. In: multi-element supplement for grazing sheep. I. Trace Elements in Animal Products and Vete­ Intake, mineral status and production rinary Practice. British Society Animal Pro­ responses. Australian Journal of Agricultural duction, Occasional Publication No. 7, ] 9-25. Research, 43. 795-808.

94 Toxicities and Excessive Intakes of Minerals

John McC. Howell

School of Veterinary Studies Murdoch University Perth, Western Australia 6150 Australia

Outline

Exposure and interactions Diagnosis History of exposure Clinical features Morphological change Biochemical tests Analyses of diet, tissues and body fluids Toxic syndromes Zinc Copper Manganese Cobalt Molybdenum Selenium Fluorine Arsenic Lead Cadmium Miscellaneous minerals Limitations for human consumption Acknowledgments References

9S DETECTION AND TREATMENT OF MINERAL NUTRITION PROBLEMS If'/ GRAZING SHEEP

ost of the information in this publica­ performance, ill health and possibly death M tion is about deficiencies of certain may occur when the concentration of the minerals. These minerals have to be present element within the tissues is markedly in the diet if animals are to develop, produce increased. There can be no doubt that a little and survive. They are essential minerals. of an essential element in an animal's diet is For many of the essential elements the good, but it is not true that a lot of that amount required for survival and production element in the animal's diet is even better. is very small. They are required in trace Thus there is the paradox of certain ele­ amounts. They are known as the essential ments being both necessary for, and dam­ trace elements. Even though the elements aging to, the proper functioning of cells, are essential for health, the concentration of tissues and animals. This has led to con­ the element within the tissues must be kept flicting statements such as: 'toxic elements within fairly narrow limits if normal body do not exist' or 'everything is poisonous', structure and function are to be maintained. The paradox of essentiality and toxicity is Deviation from these limits may result in resolved once it is realised that it is the con­ damage to the tissues. centration of the element within the biologi­ The limits for the concentration of the cal system that determines the type of element within tissues are determined by reaction that occurs, the efficiency of the homeostatic mecha­ Particular concentrations of trace ele­ nisms of the animal. If the homeostatic ments may result in three types of biological mechanisms can no longer handle the con­ activity: centration of the element present within the 1) low concentrations at which the element tissues, the metabolic processes within the is necessary for life; cells are disturbed, the cells are damaged 2) higher concentrations at which the and the animal is no longer normal. This element may reduce the productive may result in overt clinical illness or it may capacity of the animal and may increase result in subclinical disease manifesting as susceptibility to inter-current disease; poor performance in such things as weight 3) concentrations at which a toxic clinical gain, fleece growth, the ability to carry a syndrome is clearly recognisable foetus to term or milk production. In addi­ (Howell 1983). tion the animal may have an enhanced sus­ ceptibility to other diseases such as those Exposure and Interactions produced by toxins or infectious agents. If the concentration of an essential The requirements for trace elements element within an animal's tissues is depend upon a variety of factors including reduced it is entirely predictable that the the overall constitution of the diet, the stage animal would no longer function normally of growth, magnitude of production, stage and might show a drop in production or of pregnancy and the genetic makeup of the become clinically ill or die. It is not always animal. Changes to any of these factors understood that the development of poor may influence whether a particular concen-

96 TOXIClTlES AND EXCESSIVE INTAKES OF MINERALS - J.McC HOWELL tration of a mineral is deficient, sufficient or prevented by the oral administration of zinc toxic. supplements. This treatment is widely used Animals may become exposed to toxic but has sometimes resulted in the develop­ concentrations of minerals in a variety of ment of zinc toxicity. The development of ways, but the two most important by far are zinc toxicity seems to be particularly by administration as a therapeutic sub­ common when the zinc solution is given by stance or by ingestion with the feed. Iatro­ drenching gun, as this may stimulate the genic, or therapy induced, damage may rumeno-reticular groove and the dose may occur following attempts to treat or prevent go straight into the abomasum from where deficiency states and the therapy for copper it is absorbed quickly (Smith et al. 1979). deficiency in sheep is a good example. A The most common way in which an great number of ways have been developed animal becomes exposed to toxic concen­ to administer copper so as to prevent the trations of minerals is by ingesting them in development of copper deficiency in rumi­ the feed. This may be due to environmental nants and one of these ways involves the contamination which most frequently arises subcutaneous injection of copper com­ when animals are grazing pastures close to plexes. smelters, mineral processing plants or old However, use of these copper complexes mine sites, or are consuming foods har­ has sometimes been followed by the death vested from their vicinities. The two most of a variable proportion of the injected commonly cited toxicities that arise in this sheep. Some of these animals developed a way are those of fluorine and lead (Lloyd haemolytic crisis and examination of their 1983) but copper toxicity in ruminants may tissues revealed the changes of copper poi­ also be due to industrial contamination of soning. It was found that the organic com­ pasture (Gummow et al. 1991; Vrzgulova ponents of the complexes in which the 1993). copper was given markedly increased its Alternatively, the toxic concentration may absorption and toxicity (Ishmael et al. 1971; have resulted from the incorrect formulation Mahmoud and Ford 1981). of a ration or mineral mix. This may have Another example is provided from the arisen from a clerical error such as having, New Zealand work on facial eczema which within the formula, a decimal point in the is seen as a disease of sheep and cattle wrong place, or by having an imbalance of grazing pastures infected with the fungus elements, or by human error during mixing, Pithomyces chartarum. This fungus pro­ or by environmental contamination of the duces an hepatotoxin called sporidesmin. feed, or a component of the feed. These The toxin damages the liver cells, resulting may be simple mistakes, or they may arise in photosensitisation, and the major due to ignorance of the variability of toler­ damage is seen as inflammation and ance for these elements from one species to destruction of the skin of the head-hence the next. the term 'facial eczema'. The disease can be Consider a particular farming enterprise so severe that it results in death. It may be involving sheep and pigs. A mineral mix

97 DETECTION AND TREATMENT OF MINERAL NUTRITION PROBLEMS fN GRAZING SHEEP designed to increase the production of pigs biological life. The interactions between ele­ could work well for the pigs but fatalities are ments are complex and specific examples likely if the same mix is fed to the sheep. A are given elsewhere in this paper. concentration of 4 mg copper jkg of dry The bioavailability of a mineral in the diet matter in the diet is adequate for growing may depend upon such factors as its pigs of up to 90 kg live weight (ARC 1967), physicochemical form and the protein and but Braude and Ryder (1973) showed that vitamin content of the ration. This is partic­ supplementing the ration to contain 250 mg ularly important in monogastric species copper jkg dry matter greatly increased the where ascorbic acid reduces the toxicity of liveweight gain and efficiency of feed use in several elements and phytic acid binds pigs. Thus manufactured feed for pigs often copper and zinc and renders them less contains these high concentrations of available for absorption (Davies and Night­ copper. ingale 1975). A diet in which the main The recommended level of copper in the protein component is of plant origin, such feed of sheep is 5 mgjkg dry matter (ARC as soya bean, cottonseed or sesame meal, 1965), yet Hartmans (1975) reported that will be high in phytic acid and will have a diets containing more than 15 mgjkg dry great capacity to bind copper and zinc. A matter were dangerous for sheep and cases similar concentration of copper or zinc in a of copper poisoning have been reported in ration in which the main source of protein is sheep fed on mixed hay and concentrate of animal origin will have the potential to be diets containing less than 10 mg copper jkg more toxic. This interaction with phytate dry matter (Hogan et al. 1968; Todd 1969; has not been found in ruminants, due to Buck 1970). Therefore it would be poten­ breakdown of phytate by rumen micro­ tially disastrous to formulate a single organisms. mineral mix to be fed to both the species on Grazing animals may ingest differing con­ this farm. centration of minerals according to the It is also potentially dangerous to change stages of development of their pastures, for a single item in a diet without having due the mineral composition of plants varies regard for the effects that this may have on between species, within species and at other components of the diet. Underwood various stages of growth. Improving pasture (1981) wrote 'The significance of overall through the application of fertilizer usually dietary balance for the absorption and utili­ leads to changes in the botanical composi­ sation of mineral nutrients by animals tion and may lead to substantial changes in cannot be overstressed'. Interactions the mineral content of mixed herbage. In between minerals can occur in the environ­ times of drought animals will also be ingest­ ment, in the feed, or in the alimentary tract ing considerable quantities of soil and this and may significantly alter the biological will influence the intake of minerals (Howell availability of the trace element, its absorp­ 1983). It is also important to realise that tion from the gut, its transport and distribu­ some plants are capable of absorbing min­ tion within the body and its effective erals from the soil even though the mineral

98 fOXIClTlES AND EXCESSIVE INTAKES OF MINERALS - J.McC HOWELL

may be present in very small quantities or in seen in control sheep, nor did it produce a form relatively unavailable to other plants significant clinical illness. However, the growing alongside. administration of copper to sheep at the This is true of the selenium accumulator same time as, or subsequent to, the inges­ plants such as Astragalus racemosus tion of heliotrope markedly increased the which will grow only in areas where there is accumulation of copper in the liver, resulted a high concentration of sE\Jenium in the soil. in significant liver damage in all sheep and There are more than 250 species of Astrag­ clinical illness in the majority. The copper alus growing in China (Cao et al. 1992). accumulation, tissue damage and clinical Selenium accumulator plants absorb forms illness in these sheep was far greater than in of selenium which are not taken up by other sheep given the same dose of copper alone plants. The selenium is incorporated into (Howell et al. 1991a,b, 1993). organic forms which are then available to There is increasing evidence that genetic grazing animals. These animals may factors influence the way in which animals develop selenium toxicity. In addition when absorb, transport and retain such elements the unconsumed parts of the plant die, the as selenium, copper, iodine, zinc and iron selenium within them is returned to the soil (Wiener and Woolliams 1983; Wiener 1987). in forms which may be available to the non­ Most of this work has been done on sheep accumulator plants. Thus the selenium and it is possible to say that dietary amounts content of the total plant population may of copper that are adequate for some breeds increase. will be inadequate for others and possibly Toxins other than minerals may play a toxic for some. In studies of 231 samples of significant role in mineral toxicity. This is the sheep liver, Meyer and Coenen (1994) found case when the presence of the mineral and a range of concentrations of copper. From the other toxin within the tissues leads to a 198 of the samples from adult sheep 28% synergistic toxic action. A good example is suggested copper deficiency and 21 % sug­ provided by a syndrome which is of eco­ gested copper overload. nomic importance in the Australian sheep Sheep of the Heidschnuke breed com­ industry. The syndrome is called hepatoge­ prised the main part of those with the lesser nous copper poisoning or 'the Yellows' of concentration; Merino and T exeJ sheep were sheep. Animals developing the Yellows predominant in the group with the elevated become jaundiced, may develop a haemo­ concentration. It has been known for some lytic crisis and may die. The syndrome is time that the Texel breed of sheep has a seen when sheep ingest both copper and greater susceptibility to copper poisoning pyrrolizidine alkaloids such as those found than other breeds (Luke and Wiemann in senecio, echium and heliotrope plants. 1970). Housing Texel sheep and feeding It has been shown experimentally that the them grain-based concentrate feeds may feeding of heliotrope alone produced liver well result in copper toxicity in situations damage but did not induce a greater accu­ that would not be detrimental to other mulation of copper in the liver than that breeds.

99 DETECTION AND TREATMENT OF MINERAL NUTRITION PROBLEMS IN GRAZING SHEEP

Diagnosis clouds of smoke, gas and particles. In that situation making a diagnosis is assisted by Earlier in this paper it was stated that the presence of a time factor, multiple mineral toxicity may result in clinical animals involved with a similar syndrome, disease, loss of production or increased and visual evidence of contamination. susceptibility to other disease states. When However, one would still need to be mindful clinical disease (such as fluorosis or chronic of all the other factors and take into consid­ selenium toxicity or chronic copper poison­ eration the differential diagnosis. Evidence ing) develops it is relatively easy to make a of exposure is not obvious in the situation diagnosis. However, in other situations sub­ where human error has occurred in mixing clinical effects leading to loss of production or administering a mineral supplement, make diagnosis more difficult and a consid­ particularly if the supplement had previ­ erable amount of production may be lost ously been used in the correct amount. In before a correct diagnosis is made. In this instance analysis of the food and the attempting to make a diagnosis of mineral tissues of the animals will provide the most overload one must: valuable clues. look for a history of exposure; take notice of any clinical features; Clinical features examine the morphological changes in material obtained by biopsy or at post­ When a clear-cut toxic syndrome devel­ mortem examination; ops the clinical features will be of great use appropriate ancillary biochemical value, as they would be in fluorosis or tests; chronic copper poisoning. However, if the analyse the mineral content of diet, degree or pattern of toxicity does not tissues and body fluids. produce an overt clinical problem but It must be stressed that in making a diag­ results in subclinical problems such as loss nosis, all of these factors should be taken of production, the diagnosis is much more into account. Considering only one cate­ difficult because the causes of production gory may lead to wrong decisions. Some of loss are many and varied. In this case it is the tissue changes and clinical signs seen in essential to use all the parameters indicated mineral toxicities may be produced by a above. In addition a response to treatment variety of other factors, so consideration would be of value. should always be given to a differential diagnosis. Morphological change When one is involved with a flock problem History of exposure it is often sensible and economically viable A history of exposure may be obvious if a to sacrifice one-or better two or three-of specific problem has arisen in a number of the affected animals in order to look for animals that have grazed for some time morphological changes in all tissues. Such down-wind of a smelter belching forth a procedure also enables the sampling of

100 TOXIC/TIES AND EXCESSIVE INTAKES OF MINERALS - J.McC. HOWELL

multiple tissues for the analysis of their nase in the blood will indicate that changes mineral content. If it is not possible to sacri­ are occurring in muscle and liver respec­ fice animals, consideration should be given tively but do not indicate the nature of the to taking a biopsy. Biopsy of the liver (Dick agent which produced the damage. 1952; Donald et al. 1984) is relatively easy and safe to perform on sheep. Biopsy of Analyses of diet, tissues and body fluids bone is sometimes useful and a technique is illustrated by McDowell et al. (1983). Bone Analysis of body fluids for concentrations can also be obtained as a coccygeal verte­ of particular minerals is useful but should be bra by removing the end of the tail. These combined with analYSis of the feed and methods should provide sufficient tissue for wherever possible of storage organs such as morphological examination and chemical liver and kidney. It is obviously important to analysis. Morphological changes alone can obtain the correct sample for analysis. strongly indicate a particular mineral toxic­ Always try to ensure that the feed sample ity, such as fluorosis and chronic copper was taken from the food ingested by the poisoning. More often they will provide a animals during the development of toxicity valuable indication of which mineral and that the methods of sampling and requires further investigation. transport have not caused contamination. Blood, urine, saliva and hair are frequently Biochemical tests analysed because they can be obtained without killing the animal. Ancillary biochemical tests on body fluids It should always be remembered that the such as blood will often indicate the organ homeostatic mechanisms will be endea­ involved but only rarely do they specifically vouring to keep the concentration of miner­ identify the particular mineral. A decrease in als in the blood within the normal limits. the activity of o..aminolaevulinic acid dehy­ Nevertheless there can be great variations dratase in the red blood cells is found in between individuals in the concentration of cases of lead poisoning in sheep and is a a particular element in the blood. For these reasonably specific indicator of lead over­ reasons more information will be obtained load. However the level of o..aminolaevulinic from multiple blood samples from individu­ acid in urine was found to vary too greatly to als than from single samples. If the problem be of value as a diagnostic test (Rolton et al. arose from recent exposure, analYSis of 1978). Using blood samples from calves on ingesta, faeces and urine might be of a farm contaminated with lead-based paint value. Wada et al. (1993) found that estimation of If the diet in question had been consumed free erythrocyte protoporphyrin concentra­ over a long period then the major storage tion was a good indicator of lead contami­ organ for the particular mineral should be nation. Other tests such as those which sampled. This will often be the liver. It should indicate consistent increases in the activity also be remembered that chemical analysis of creatine kinase or glutamate dehydroge- will give the amount present, but will not

101 DETECTION AND TREATMENT OF MINERAL NUTRITION PROBLEMS IN GRAZING SHEEP

indicate the bioavailability. For example, the levels of zinc. Calcium, copper, iron and concentration of copper in the blood and cadmium have all been shown to interact in kidney from clinically normal but copper­ the processes of absorption and utilisation loaded sheep dosed with tetrathiomolybdate of zinc. Young animals seem to be more to prevent copper poisoning will be much susceptible and Davies et al. (1977) con­ higher than in normal sheep (Howell and cluded that suckling lambs were considera­ Kumaratilake 1990). However, much of the bly more susceptible to zinc toxicity than copper in the sheep given tetrathiomolyb­ were mature ruminants. They reported poor date will be biologically unavailable. growth, low appetite and extensive kidney It may be necessary to perform chemical damage in suckling lambs maintained for 4 analysis on more than one organ and to weeks on a milk substitute diet containing combine chemical analysis with morpho­ T oprina yeast with a content of 2065 mg logical analysis. For example, two sheep zinc/kg dry matter. Renal damage was also may contain similar concentrations of seen in lambs fed a milk diet supplemented copper in the liver, but if only one animal with an equivalent amount of zinc. has necrosis of the centrilobular liver cells it Pregnant ewes are more susceptible to is probable that this animal died of chronic zinc toxicosis than non-pregnant sheep copper poisoning and that the other died of (Campbell and Mills 1979) and this might something else. The diagnOSis of chronic be due to an increase in the efficiency of copper poisoning would be confirmed if it zinc absorption during pregnancy (Bremner was found that the sheep with the necrotic 1979). Smith et al. (1979) have shown that liver cells also had elevated concentrations the toxicity of zinc given to prevent the of iron and copper in the kidney, indicating development of facial eczema was that significant haemolysis had occurred. enhanced when zinc sulfate was given by drenching gun. Administration of zinc solu­ Toxic Syndromes tions by drenching gun resulted in increased concentrations of zinc in serum and organs, In the toxic syndromes outlined below some severe lesions in the abomasum and pan­ indication is given of toxic concentrations creas and even death, even though the but no attempt is made to give 'safe levels'. same dose was apparently non-toxic when This is because of the interactions outlined delivered by intraruminal intubation. These above and also the variation of animal authors suggested that the administration of response that follows a single exposure or zinc solutions by drenching gun resulted in repeated exposures to toxic concentrations contact of zinc with the pharyngeal mucosa of a mineral. Table 1 summarises the find­ which resulted in stimulation of the reticular ings. groove reflect and direct channelling of the solution into the abomasum. The resulting Zinc damage to the mucous membrane might Domestic animals appear to have a con­ also result in an increased rate of absorp­ siderable tolerance to diets containing high tion.

102 TOXICfTlES AND EXCESSIVE INTAKES OF MINERALS - J.McC. HOWELL

Table I. Indication of the concentrations, interactions, signs and tissues damaged by high concentrations of minerals (adapted from Howell 1983). This summary is not exhaustive; the text and the references cited in the text should be consulted.

Element Species Toxic Interactionsb Signs Tissue damage commonly concentrationsa affected

Zinc Sheep [ 33-1 00 mg Zn/kg Ca, Cu, Fe, Cd, Reduced weight gains, Many tissues but, Cattle body weight death particularly pancreas, 750-2000 mg/kg DM abomasum and kidney in diet

Copper Acute Lambs 25-50] mg/kg body Abdominal pain, Alimentary tract Cows 200 weight diarrhoea

Chronic Sheep 10-201 mglkg Zn, Fe, Cd, Mo Inappetence. soft faeces, Blood, liver, kidney, muscles, Goats 10-20 DM + S, dark red urine, jaundice brain Calves 115 in diet Ascorbic acid and death

Manganese Sheep 400 mg/kg DM in diet Fe Reduced growth rate

Cobalt Cattle I Jmglkg body Fe Inappetence, loss of Sheep 4-10 weight weight, occasionally death

Molybdenum Cattle [20-100 mg/kg DM Cu and S, Zn. Pb, Inappetence, weight loss, Bones, joints. testes Sheep in diet methionine. cystine diarrhoea. irregular oestrus cycles

Selenium Cattle [5-30 mg/kg DM Dietary protein, Respiratory distress. Heart, liver, bones, joints, Sheep in diet As, Hg, Ag, Cu, Cd, diarrhoea, loss of blood S, methionine, weight, blindness, vitamin E paralysis, loss of hair and hooves

Fluorine Chronic Yearly average in diet AI, Ca Growth retardation, Teeth and bones Cattle for cattle must be 40 inappetence, weight loss, Sheep mg F/kg DM or less, lameness and intake must not exceed 60 for more than 2 months or 80 for more than I month Continued on next page.

103 DETECTION AND TREATMENT OF MINERAL NUTRITION PROBLEMS IN GRAZING SHEEP

Table I. Cont'd.

Element Species Toxic Interactions b Signs Tissue damage commonly concentrationsa affected

Arsenic Inorganic Varies as composition Se Acute gastroenteritis, Alimentary tract All species and solubility, ete. death

Lead All species 3 mg/kg DM in diet. Ca, P, Fe, Cu, Zn, Anaemia, diarrhoea, Liver, kidney, blood. 5-20 mg/kg body vitamin C constipation, hyper- alimentary tract, central weight. Great variation excitability, tremor. and peripheral nervous according to source ataxia, death system, bones and species etc. a The figures given in this column provide. where possible, an indication o( the doses and ranges at which signs o( toxicity have been reported. b Symbols (or elements: Ag. silver; AI. aluminium; As. arsenic; Ca. calcium; Cd. cadmium; Cu. copper; F. fluorine; Fe. iron; Hg. mercury; Mo. molybdenum; P. phosphorus; Pb. lead; S. sulfur; Se. selenium; Zn. zinc.

Inflammation of the abomasum and ing in sheep by giving doses of 35 mg zinc necrosis of the pancreas have been asso­ oxide/kg body weight on 5 days of the ciated with the administration of high con­ week, but lesions of zinc toxicity were found centrations of zinc in order to prevent the in the pancreas. Smith and Embling (1993) development of facial eczema and lupinOSiS have shown that the pancreatic lesions are in sheep. Alien and Masters (1980) and evident 7 days after treatment and take up Alien et al. (1983) have written comprehen­ to 4 weeks to develop fully. sive accounts of zinc toxicity in the rumi­ nant. They described the changes seen in Copper naturally occurring and in experimentally induced zinc toxicity in sheep and calves. Copper interacts metabolically with many Pathological changes were found in the other substances including zinc, iron, pancreas, kidney, Jiver, rumen, abomasum, cadmium, molybdenum, sulfur and ascor­ smaH intestine and adrenal gland. However, bic acid. Therefore it is hazardous to give a the pancreas was the only organ to be con­ maximum safe dietary level based on sistently affected and degeneration and copper values alone. Sheep are particularly regeneration often occurred together. susceptible to copper poisoning and the Many of the affected sheep developed increased susceptibility may be associated anaemia. Elevated concentrations of zinc with several factors. Bremner (1980) has were usually found in the liver, kidney and suggested that the greater susceptibility of pancreas. Noordin et al. (1993) successfully sheep and calves to chronic copper poison­ used zinc to prevent chronic copper poison- ing could be related to their inability to

104 TOX/CITIES AND EXCESSIVE INTAKES OF Mlf'IERALS - J.McC. HOWELL

accumulate large amounts of copper as there would be a minimum risk of copper monomeric metallothionein in their livers. In toxicity if substances such as molybdenum addition they are often fed cereal-based and sulfur were added to dried poultry waste rations which are low in molybdenum and in order to make it safe for use as a cheap sulfur and from which copper is more easily nitrogen source for rumina nts. absorbed. It has been suggested that this In Australia phytogenous copper poison­ may account for the marked increase in ing has been seen in sheep grazing pastures susceptibility to copper poisoning seen in with a high content of the clover Trifolium housed sheep, which are commonly fed subterraneum which may contain 10-15 such rations (Todd 1972). mg copper/kg dry matter but in which the Acute poisoning with symptoms of acute molybdenum content rarely exceeds gastroenteritis sometimes occurs but the 0.1-0.2 mg/kg dry matter. Such conditions most commonly encountered form of greatly favour copper accumulation. Hepa­ copper toxicity is known as chronic copper togenous copper poisoning has occurred in poisoning. This may be primary copper grazing sheep when plants containing poisoning due to the ingestion of too much hepatotoxic pyrrolizidene alkaloids such as copper, phytogenous copper poisoning due Heliotropium europaeum, were growing in to the ingestion of plants with a high copper the pasture. Care should always be taken to content with or without a low concentration ensure that the feed for sheep does not have of molybdenum, or hepatogenous copper a high copper content and has a balanced poisoning where the liver is damaged by copper:molybdenum:sulfur ratio (see plant toxins prior to or in conjunction with White, this publication). the ingestion of copper. Mention has already been made in this Grazing sheep are relatively safe unless paper of possible problems which may arise there has been a recent a pplication of when sheep have access to diets prepared copper to the pasture. One of the first for pigs; on occasion diets prepared for authentic reports of primary copper poison­ cattle may also cause problems (Robles et ing in sheep occurred when animals were at. 1993). allowed to graze in orchards after the fruit There are three phases of chronic copper trees had been sprayed with copper sulfate poisoning, namely the prehaemolytic, solution to combat insect pests (Schaper haemolytic and posthaemolytic. The pre­ and LOtje 1931). POisoning with associated haemolytic phase may last for weeks and liver damage has been reported in sheep during this time copper accumulates in the grazing pasture sprayed with copper-rich tissues of clinically normal animals. The pig slurry (Ulsen 1972; Kneale and Howell haemolytic phase is the time of the so-called 1974). However, holding the pig slurry in an haemolytic crisis. Haemolysis may be anaerobic tank for 60 days made the copper induced by stress, occur suddenly and may unavailable to herbage (Kneale and Smith be severe or mild. The animals may have a 1977). Animal excreta are rich in nitrogen haemolytic anaemia, with haemoglobin­ and SuttIe and Price (1976) suggested that aemia, methaemoglobinaemia, haematuria

105 DETECTION AND TREATMENT OF MINERAL NUTRITION PROBLEMS IN GRAZING SHEEP and jaundice. Severely affected animals may required to prevent the development of clin­ be dull and lethargic, pass soft faeces, lose ical signs, and significantly reduce liver their appetite and have an excessive thirst injury and copper accumulation. At the and the sclera may show the chocolate higher dose rate pancreatic lesions were brown colour of methaemoglobin. The present. animals may die, or recover to move into the posthaemolytic phase, during which other Manganese bouts of haemolysis may develop. The prin­ cipal sites of tissue damage are the liver and Manganese poisoning is rare, but in some kidney but changes also occur in other New Zealand pastures manganese levels organs. The condition in sheep has been can be above 500 mg/kg dry matter. At reviewed by Howell and Gooneratne (1987). these high manganese intakes the rate of Several workers have used the oral growth of young sheep is significantly administration of ammonium molybdate reduced (Grace 1973). A relationship (50-500 mg) and sodium sulfate (0.3-1 g) between manganese, iron and haemoglobin given daily for up to 3 weeks in attempts to formation has been demonstrated in lambs reduce tissue levels of copper and to and pigs (Hartman et al. 1955; Matrone et al. prevent the development of haemolysis in 1959) and probably arises because of a sheep flocks in which copper poisoning had mutual antagonism between manganese been diagnosed (Ross 1966; Hogan et al. and iron during absorption. 1968; Kline et at. 1971). Tetrathiomolybdate was first used in experimental situations to Cobalt treat and prevent chronic copper poisoning Most animal species seem tolerant to high in sheep by administering the agent by the concentrations of cobalt. This is so in rumi­ intravenous route (Gooneratne et at. 1981). nants but some evidence suggests that Subsequently Humphries et al. (1988) suc­ cattle are less tolerant than sheep. The cessfully gave three subcutaneous injec­ reports have usually indicated that the signs tions of 3.4 mg tetrathiomolybdate/kg body of excess in cattle were reduced appetite weight, on alternate days, to successfully and weight loss, but Dickson and Bond treat and prevent copper poisoning. (1974) reported five cases of fatal cobalt The use of 175-375 mg zinc/kg of feed in poisoning. A cardiomyopathy has been sheep fed diets high in copper may prevent seen in man following the heavy consump­ the development of copper toxicosis tion of cobalt-fortified beer but this change (Bremner et al. 1976). Noordin et al. (1993) has not been reported in cobalt-overloaded gave either 17 or 35 mg zinc oxide/kg body animals. weight by mouth on 5 days per week to prevent the syndromes of copper, heliotrope Molybdenum and hepatogenous (heliotrope/copper) poi­ soning in sheep. Both dose regimens had a The tolerance of farm animals to toxic beneficial effect but the higher dose rate was concentrations of molybdenum varies

106 TOXICITIES AND EXCESSIVE INTAKES OF MINERALS - J.McC HOWELL

according to the species, the chemical form also been reported in the interstitial cells of the ingested molybdenum and the and germinal epithelium of the testes (see copper status of the animal. The status of Underwood 1977). the diet with regard to protein, copper, Sharma and Parihar (1994) gave ammo­ sulfur, zinc, lead, methionine and cystine nium molybdate by mouth to young goats are also of importance. Pigs and horses every day for 235 days-treatments were 0, appear to be more tolera(lt than sheep and 50 and 100 mg molybdenum/kg of feed cattle and it has been known for many years intake on a dry matter basis. The concen­ that horses may safely graze the molybde­ trations in the blood of copper and caerulo­ num-rich so called 'teart' pastures which will plasmin were reduced. Clinical signs, which produce marked diarrhoea in ruminants. developed first in the 100 mg/kg group, Exposure to high concentrations of were diarrhoea, anaemia, reduced body molybdenum causes growth retardation, weight, weakness, unthriftiness, depigmen­ weight loss and anorexia in all species but tation of the hair and altered reproductive diarrhoea was seen as a conspicuous clini­ performance. cal feature only in cattle. Within a few days Many signs of molybdenum toxicity are of grazing 'teart' pastures containing 20- associated with the induced hypocuprosis. 100 mg molybdenum/kg dry matter, cattle When either ammonium molybdate or tet­ may scour profusely and develop harsh, rathiomolybdate was given to pregnant staring coats. Treatment with copper sulfate guinea pigs, the concentration of copper in at the rate of 2 g/day for cows or 1 g/day for the liver was reduced and that of molybde­ young stock may effectively control the num was elevated. Death of the foetus was scouring (Ferguson et al. 1938). common in guinea pigs given the higher Outbreaks of molybdenum toxicity result­ dose of thiomolybdate. This, together with ing in severe diarrhoea in cattle have been degeneration of the pancreas, was thought reported following the discharge of waste to be due to induced hypocuprosis (Howell waters containing molybdenum ore into the et a/. 1994). High concentrations of molyb­ Nanle river (Li et aL 1994) and following the denum in the tissues have been associated pollution of cultivated land by waste water with irregular oestrus cycles in cattle but not containing molybdenum ore in Dayu with damage to the foetus (Phillippo et al. county, Jiangxi province in China (Fan et al. 1985). 1983). Sheep were also affected and they lost wool and became anaemic. The Selenium animals recovered after copper sulfate was given as 'two doses of 1 g/45 kg body The toxicity of selenium may vary weight'. Changes in bones and joints have according to the chemical form of the also been reported, as have difficulties in ingested selenium and the duration and conception in cows and loss of libido in continuity of intake. The toxicity of sele­ bulls. The latter may be associated with the nium may be decreased by increasing bone and joint lesions but changes have dietary protein, arsenic, mercury, silver,

107 DETECTION AND TREATMENT OF MINERAL NUTRITION PROBLEMS IN GRAZING SHEEP copper, cadmium and sulfur compounds, ince. The authors reported that a selenium linseed meal, methionine and vitamin E content of blood over 2.5 J.lmoljL can be (Underwood 1981; Cooper 1987). Elemen­ regarded as an early diagnostic index of tal selenium is well tolerated because of its toxicity and that symptoms will appear insolubility and poor absorption. Selenides when the concentration of selenium in blood are less toxic than selenites or selenates and and wool exceed 6.25 J.lmoljL and 38 the forms of selenium found in plants J.lmoljkg respectively. appear to be even more toxic. It is worth The toxic selenium intakes may arise noting that sodium selenite contains 1.93 from the ingestion of plants that have con­ times as much selenium as sodium selenate centrated selenium in their foliage and and this has contributed to accidental sele­ seeds. Plants may be subdivided into obli­ nium poisoning in sheep (Kyle and Alien gate accumulators (which require high 1990). levels of selenium for their development), It is probable that the majority of deaths facultative accumulators and non­ of animals due to selenium toxicity result accumulators. Obligate accumulators, such from miscalculation of dose or the use of as Astragalus species, are also known as incorrect preparations. Increasingly sele­ indicator plants as they only survive in soils nium is being added to injectable vaccines rich in selenium and may accumulate con­ and anthelmintics. In this way it has become centrations of over 1000 mg/kg selenium. an integral part of the disease prevention These plants absorb selenium from the soil program in many flocks. However, care even though it is in forms relatively unavail­ should be taken to ensure that only appro­ able to other plant species. Within the plant, priate doses are given to lambs. A dose of the selenium is converted into organic unsupplemented vaccine prepared for ewes forms which are available to animals will do no harm if given to lambs but lambs grazing the plants. When unconsumed parts may well develop selenium toxicity if the of the plants die, the selenium is returned to vaccine also contained the dose of selenium the soil in forms available to non­ suitable for ewes. Additional problems arise accumulator plants. Facultative accumula­ when animals receive selenium from two tors take up large amounts of selenium sources simultaneously (Bruere et al. from soils containing normal concentra­ 1990). tions of selenium. Non-accumulator plants Selenium toxicity occurs primarily in take up large amounts of selenium only cattte, sheep and horses in the so-called when they are growing in seleniferous soils. 'seleniferous areas', which occur in many The selenium toxicity syndromes can be parts of the world including China (Cheng et classified into three types. These are, the al. 1980). In these areas the soil may acute, subacute ('blind staggers') and contain in excess of 500 mg/kg of selenium. chronic ('alkali disease') form~. Acute tox­ Hou et a!. (1993) reported selenosis in goats icity results in respiratory distress, diarrhoea that had been fed maize grown in selenium­ and death. Animals showing the 'blind stag­ toxic land in Ziyang county, Shaanxi prov- gers' syndrome may wander, stumble, have

108 TOX/CITIES AND EXCESSIVE INTAKES OF MINERALS -J.McC. HOWELL

impaired vision, paralysis, abdominal pain, water from boreholes (Botha et al. 1993) salivation, grating of the teeth and respira­ and following volcanic eruptions (Araya et tory distress. Animals with chronic selenium al. 1993). East (1993) reported fluorine, poisoning show lack of vitality and body calcium pyrophosphate and calcium condition, roughness of coat, sloughing of orthophosphate poisoning in 41 out of 200 the hooves, articular lesions and lameness, pregnant ewes after consumption of super­ changes in the myocardium, cirrhosis of the phosphate fertilizer-the consumption of liver and anaemia. There may be loss of hair which was thought to be related to the lack from the mane and tail of horses and body of salt availability. of pigs. It has been suggested (James et al. Poisoning may be seen as an acute 1994) that 'blind staggers' is due to dietary episode of gastroenteritis, usually in pigs factors other than selenium, such as sodium following the ingestion of an excessive sulfate, and that the symptoms and lesions amount of sodium fluoride, or as the chronic \ are those of polioencephalomalacia (Howell syndrome of fluorosis in ruminants, pigs 1961). and horses. Fluorosis is associated with the Quin et al. (1994) gave six goats a diet long term ingestion of contaminated feed. containing 11 mg selenium/kg fed for 60 Suttie (1981) pointed out that the current days. The animals showed depression, tolerance level established for the continual inappetence, loss of hair, pruritus, increase ingestion of a soluble fluoride by young in heart rate and respiratory distress and dairy cattle is 40 mg fluorine/kg dry matter they died as a result of respiratory failure. in the total ration but recommended that the Lesions were found in lungs, liver, kidney, yearly average forage concentration should heart, brain, lymph nodes and spleen. The not exceed 40 mg fluorine/kg dry matter, mechanisms underlying these toxic actions and it should not exceed 60 mg fluorine/kg are poorly understood and it may be that for more than 2 months or 80 mg fluorine/kg al kaloids and other toxic substances in the for more than 1 month. Fluorosis has plants may also have a part to play in the occurred in Inner Mongolia, Xinjiang and subacute and chronic forms (see Ewan other areas of China where pastures, forage 1978; Underwood 1981). and/or drinking water were contaminated by airborne residues from industrial pro­ Fluorine cesses or where the fluorine in soil was plentiful (Deng 1989; Guo et al. 1990). Most pasture plants, forages and grains Wang et al. (1992, 1994) examined goats have a low fluorine content. However, sig­ that had been grazing pasture which was nificant contamination can arise in pasture severely polluted by fluorine coming from a close to smelters and mineral processing nearby industrial plant. They suggested that plants (Uoyd 1983). Pasture contamination dry and cold weather conditions led to has also been reported due to fluorine con­ excessive concentrations of fluorine in the tained in superphosphate fertilizers (O'Hara grass consumed by animals, resulting in the et al. 1982), excessive contamination of development of osteoporosis, and that

109 DETECTION AND TREATMENT OF MINERAL NUTRITION PROBLEMS IN GRAZING SHEEP

differences in fluoride and calcium ciated with acute arsenic poisoning are availability during different seasons resulted those of an acute gastroenteritis. in uneven abrasion of teeth and a shortened The incidence of arsenical poisoning in life span. Tooth wear decreased with farm animals has declined due to the increased protein supplementation. marked reduction in the use of arsenical The major changes in animals suffering compounds. However, in recent years a from chronic fluorosis are seen in the teeth large number of cases of arsenic poisoning and bones. Animals exposed to excess fluo­ has been reported in humans due to arsenic rine before eruption of the permanent teeth contamination of water from deep tube develop pitted, mottled, incisors and wells. It has been estimated that there are at abraded molars. There are changes in least 50000 such cases in Inner Mongolia shape and colour of the teeth and fractures (Pearce 1995) where sheep are also being may occur. Thickenings, outgrowths and affected (Lee, pers. comm.). changes in shape of the jaw and long bones can occur in animals exposed at any age. Lead These bones may appear to be chalky, rough and porous. Mineralisation of tendi­ Lead ingestion is one of the most nous attachments may occur. Growth is common causes of poisoning in the often subnormal and weight loss is often domestic animal. The common sources are associated with a reduction in milk produc­ lead-bearing paints, consumed directly or tion and fertility. The impairment of these indirectly, e.g. in silage taken from lead­ facilities may, in some part, be due to painted silos, metallic lead and soluble lead reduced feed consumption brought about compounds in car batteries, golf balls or by the dental and skeletal lesions. engine sump oil, industrial and mine efflu­ ents and emissions. The absorption and Arsenic retention of ingested lead is greatly influ­ enced by the dietary levels of calcium, The toxicity of arsenic compounds varies phosphorus, iron, copper and zinc. Young considerably according to such factors as ruminants and puppies appear to be their mode of application, chemical compo­ affected by lead toxicity more commonly sition and solubility. The trivalent form is than other domestic animals, and young much more toxic than the pentavalent form. animals appear to be more susceptible than For sheep, the average total lethal dose of adults. arsenic is 3~ 1 0 g when given as arsenic tri­ The symptoms and tissue changes of lead oxide and 0.2-0.5 g when given as sodium intoxication are those associated with arsenite. Soluble preparations such as dips, anaemia, gastroenteritis and damage to the weed killers and defoliants are particularly brain and peripheral nerves leading to a dangerous and many outbreaks of acute variety of behavioural signs, blindness and poisoning have resulted from their careless paresis (Wells et al. 1976). In 'acute' poi­ use. The clinical signs and lesions asso- soning, death may occur after symptoms

110 TOXICfTlES AND EXCESSIVE INTAKES OF MINERALS - J.McC. HOWELL

have been seen for 2-3 days or less. In Health and Medical Research Council, 'chronic' poisoning animals show the occurred in kidney and sometimes in liver symptoms for several days before death (Langlands et al. 1988). occurs. Both syndromes probably result Cadmium has a long biological half life from the accumulation of lead over a period (Nordberg et al. 1985) and the concentra­ of time. A blue 'lead-line' at the junction of tion in tissues increases with age. However, gum and tooth, due to.the periodontal dep­ the fastest uptake into the kidney occurs osition of lead sulfide, may be seen in the during the first few months after weaning dog and osteoporosis has been reported in (Lee et al. 1994). Hoggets grazing pastures lambs. Degenerative lesions may be present on acidic soils and soils with a sandy­ in liver and kidney and acid-fast intranuclear textured surface had higher cadmium con­ inclusions may be found during histological centrations in kidneys than those grazing examination of these organs. Earlier in this on pastures on more alkaline soils or those paper mention was made of the usefulness with a more textured surface. Application of in diagnosis of estimations of the activity of more than 100 kg/ha of phosphatic ferti­ 8-aminolaevulinic acid dehydratase in red lizer during a 3-year period to loamy soils blood cells and of free erythrocyte proto­ was associated with a hig h cadmium con­ porphyrin concentration. centration in the kidney (Morcombe et at. 1994). The action of cadmium is influenced Cadmium by its interaction with zinc, copper, sele­ nium and ascorbic acid. Damage to a wide Cadmium is one of the most toxic metals. range of tissues has been reported following Cadmium oxide and cadmium anthranilate cadmium administration. Industrial con­ have been used for the treatment of ascarid tamination of the food and water supply in infestations in swine but, other than this, Japan has produced a syndrome of kidney domestic animals are unlikely to be fre­ damage and osteomalacia in humans quently exposed to high intakes of the called 'itaHtai' or 'ouch-ouch disease', pre­ metal. Its emetic properties would lessen sumably because of the severe pain asso­ the effects of ingesting a single large ciated with the syndrome. Many tissues amount but chronic poisoning would follow may be damaged by cadmium overload but the long-term exposure to environmental the most typical feature of chronic contamination. Cadmium has been intro­ cadmium intoxication is marked kidney duced into the West Australian environment damage (Kawai et al. 1976). Cadmium­ as a contaminant of fertilizers formulated induced metallothionein has an apparently using rock phosphate. Sheep and cattle paradoxical role in the development of grazing on fertilised and improved pastures lesions of cadmium toxicity. It has been accumulated cadmium in their tissues and shown to protect against acute, cadmium­ concentrations exceeding the maximum induced, testicular necrosis but the permissible concentration (MPC) of 22 cadmium-metallothionein complex accu­ Ilmoljkg, set by the Australian National mulates in the kidney and is thought to be

I11 DETECTION AND TREATMENT OF MINERAL NUTRITION PROBLEMS IN GRAZING SHEEP responsible for the subsequent renal dam­ Department of Primary Industries and age (Nordberg et al. 1975). Energy. This survey found that 14.7% of sheep kidney samples and 11.3% of sheep Miscellaneous minerals liver samples exceeded the MPC for cadmium, and 4.5% of sheep liver samples Toxicity in sheep is unlikely to arise from exceeded the MPC for copper (Anon. high concentrations within the tissues of 1995). minerals such as iron, iodine, potassium, sodium chloride and sulfur. Information on these topics has been reported by Seawright Acknowledgments (1982), Howell (1983) and McDowell et al. r wish to thank Drs H. Chapman, N. Costa, ( 1983). Ms E.L. Hulm and Professor S.X. Vu for their help during the preparation of this paper. Limitations for Human Consumption References

High concentrations of minerals are also Alien, J.G. and Masters, H.G. 1980. Prevention toxic for humans and an increasing interest of ovine lupinosis by the oral administration of is being taken in the mineral content of zinc sulphate and the effect of such therapy on agricultural commodities used for human liver and pancreas zinc and copper. Australian consumption. Australia has established Veterinary Journal, 56, 168-171. Maximum Permitted Concentrations Alien, J.G., Masters, H.G., Peet, R.L., Mullins, K.R., Lewis, R.D., Skirrow, S.Z. and Fry, J. (MPCs) for some minerals in some food 1983. Zinc toxicity in ruminants. Journal of commodities. MPCs are not health or safety Comparative Pathology, 93, 363-377. levels but are set to be well below the ARC (Agricultural Research Council) 1965. The amounts required to exceed the acceptable Nutrient Requirements of Farm Livestock. No. daily intake in human food. The MPCs 2, Ruminants, London, HMSO. established as J.lmoljkg wet weight are: -1967. The Nutrient Requirements of Farm arsenic 13.4 (1.0 mgjkg) in the tissues Livestock. No. 3, Pigs, London, HMSO. tested; cadmium 22 (2.5 mgjkg) in edible Anon. 1995. National Residue Survey of Metals offal other than liver, 11 (1.25 mgjkg) in in Meat. Department of Primary Industries and liver and 1.8 (0.2 mgjkg) in meat muscle; Energy, Canberra. In preparation. copper 1575 (100 mgjkg) in edible offal Araya, 0., Wittwer, F. and Villa, A. 1993. Evolu­ other than ovine liver, 3150 (200 mgjkg) in tion of fluoride concentrations in cattle and grass following a volcanic eruption. Veterinary ovine liver and 157 (10 mgjkg) in other and Human Toxicology, 35, 437-440. tissues sampled; lead 7.2 (1.5 mgjkg) in the Botha, CJ., Naude, T.W., Minnaar, P.P., Amstel, tissue tested. During 1992-1994 a National S.R.V. and Rensburg, S.D.J.V. 1993. Two out­ Residue Survey of Metals in Meat was breaks of fluorosis in cattle and sheep. carried out by the Bureau of Resource Sci­ Journal of the South African Veterinary Asso­ ences of the Australian Commonwealth ciation, 64, 165-168.

112 TOX/CITIES AND EXCESSIVE INTAKES OF MINERALS -J.McC. HOWELL

Braude, R. and Ryder, K. 1973. Copper levels in Davies, N.T. and Nightingale, R. 1975. The diets for growing pigs. Journal of the Agricul­ effects of phytate on the intestinal absorption tural SOciety of Cambridge, 80, 489-493. and secretion of zinc, and whole body reten­ Bremner, I. 1979. The toxicity of cadmium, zinc tion of zinc, copper, iron and manganese in and molybdenum and their effects on copper rats. British Journal of Nutrition, 34, 243-258. metabolism. Proceedings of the Nutrition Davies, N.T., Soliman, H.S., Corrigal, W. and Society, 38, 235-242. Flett, A 1977. The susceptibility of sucking -1980. Absorption, transport and distribution of lambs to zinc toxicity. British Journal of l'iutri­ copper. Biological Roles of Copper. Ciba tion, 38, 153-156. Foundation Symposium. Amsterdam, Else­ Deng, P.H. 1989. Sheep diseases control in vier, 23-48. China. In: Proceedings of the Second Interna­ Bremner, I., Young, B.W. and Mills, CF. 1976. tional Congress for Sheep Veterinarians. New Protective effects of zinc supplementation Zealand Veterinary Association, Wellington against copper toxicosis in sheep. British New Zealand, 38-44. Journal of Nutrition, 36, 551-561. Dick, A.T. 1952. Improved apparatus for aspira­ Bruere, AN., Cooper, B.S. and Dillon, E.A 1990. tion biopsy of liver in sheep. Australian Veteri­ Veterinary Clinical Toxicology. Publication nary Journal, 28, 234-235. 127. Palmerston North, New Zealand Veteri­ Dickson, J. and Bond, M.P. 1974. Cobalt toxicity nary Association Foundation for Continuing in cattle. Australian Veterinary Journal, 50, Education. 236. Buck, W.B. 1970. Diagnosis of feed related toxi­ Donald, G.E. Paull, D.R. and Langlands, J.P. cosis. Journal of the American Veterinary 1984. Liver biopsy technique for assessing Medical Association, 156, 1434-1443. copper status of sheep. Australian Veterinary Campbell, J.K. and Mills, CF. 1979. Toxicity of Journal, 61, 121-123. zinc to pregnant sheep. Environmental East, N.E. 1993. Accidental superphosphate Research, 20, 1-13. poisoning in pregnant ewes. Journal of the Cao, G.R., Li, S.J., Duan, D.X., Molyneux, R.J., American Veterinary Medical Association, James, L.F., Wang, K. and Tong, C 1992. The 203, 1176-1177. toxic principle of Chinese locoweeds (Oxytro­ pis and Astragalus) toxicity in goats. In: Ewan, R.C 1978. Toxicology and adverse effects James, L.F., Keeler, R.F., Bailey, E.M., of mineral imbalance with emphaSis on sele­ Cheeke, P.R. and Hegarty, M.P., ed., Proceed­ nium and other minerals. In: Oehme, F.E., ed., ings of the Third International Symposium on Toxicology of Heavy Metals in the Environ­ Poisonous Plants. Ames, Iowa State University ment, Part 1. New York and Basle, Marcel Press, 117-121. Dekker, 445-489. Cheng, J. Y., Xu, CP., Liu, J.J., Long, J., Li, S.Q., Fan, P., Wu, Z.L., Wang, J.Y., Liu, X., Dia, Q.W., Zhou, Y.M. and Mei, Z.Q. 1980. The second Gong, Q.J., Pan, Z.J., Hu, V.X., Fang, M.H., seleniferous area investigated in China Liu, T.F. and Liu, Y.L. 1983. The study on (Ziyang County, Shaanxi Province). Reports molybdenum toxicity of farm buffalo and of Scientific Research 1970-1980, vol. 2, cattle. Chinese Journal of Veterinary Medicine, Endemic Disease, 93-101. 9,5-7. Cooper, B.S. 1987. Sheep toxicosis from sele­ Ferguson, W.S., Lewis, A.H. and Watson, S.J. nium supplementation. In: Proceedings No. 1938. Action of molybdenum in nutrition of 103 Veterinary Clinical Toxicology. University milking cows. Nature, London, 141, 553. of Sydney. The Post-Graduate Committee in Gooneratne, S.R. Howell, J.McC and Gawthorne, Veterinary Science, 175-186. J .M. 1981. Intravenous administration of thio-

113 DETECTION AND TREATMENT OF MINERAL NUTRITION PROBLEMS IN GRAZING SHEEP

molybdate for the prevention and treatment of sional Publication No. 7, British Society of chronic copper poisoning in sheep. British Animal Production, 107-117. Journal of Nutrition, 46, 457-467. Howell, J.McC., Deol, H.S. and Dorling, P.R. Grace, N.D. 1973. Effect of high dietary Mn 1991 a. Experimental copper and Heliotro­ levels on the growth rate and level of rnineral plum europaeum intoxication in sheep: Clini­ elements in the plasma and soft tissues of cal syndromes and trace element sheep. New Zealand Journal of Agricultural concentration. Australian Journal of Agricul­ Research, 16, 177-180. tural Research, 42, 979-992. Gummow, B., Botha, c.J., Basson, AT. and Howell, J.McC., Deol, H.S., Dorling, P.R. and Bastianello, S.S. 1991. Copper toxicity in Thomas, J.B. 1991 b. Experimental copper ruminants: air pollution as a possible cause. and heliotrope poisoning in sheep: morpho­ Onderstepoort Journal of Veterinary logical changes. Journal of Comparative Research, 58, 33-39. Pathology, 105,49-74. Guo, Y.X., Xu, J.G. and Cui. K. 1990. An investi­ Howell, J. McC., Deol, H.S., Noordin, M.M. and gation on chronic fluorosis in cattle in Jirem Dorling, P.R. 1993. Trace element interactions Meng, Inner Mongolia. Chinese Journal of with special reference to the interaction of Veterinary Medicine, 16, 14-15. copper and heliotrope in sheep. In: Anke, M., Hartman, R.H., Matrone, G. and Wise, G.H. 1955. Meissner, D. and Mills, C.F. ed., Proceedings Effects of high dietary manganese on hemo­ of the International Symposium on globin formation. Journal of Nutrition, 57, Trace Elements in Man and Animals. Verlag 429-439. Media Touristik. Gersdorg, 271-277. Hartmans, J. 1975. De frequentie van het Howell, J.McC. and Gooneratne, S.R. 1987. The optreden van kopervergiftiging bij schapen en pathology of copper toxicity in animals. In: de rol van het schapen-krachtvoer daarbij. Howell, J.McC. and Gawthorne, J.M. ed., Verslag van een enquete. Tijdschrift voor Copper in Animals and Man. Vol 11. Boca Diergeneeskunde, 100,379-407. Raton, Florida, CRC Press, 53-78. Hogan. K.G., Money, D.F.L. and Blayney, A Howell, J.McC. and Kumaratilake, J.S. 1990. 1968. The effect of molybdate and sulphate Effect of intravenously administered tetrathio­ supplement on the accumulation of copper in molybdate on plasma copper concentrations the livers of penned sheep. New Zealand of copper-loaded sheep. Journal of Compara­ Journal of Agricultural Research, 11, 435- tive Pathology, 103,321-334. 444. Howell, J.McC., Yu Shunxiang and Gawthorne, Hou. J.W., Qi, Z.Y., Liu, B.F. and Dong, Q.A J.M. 1994. The effect of thiomolybdate and 1993. Studies on the natural seleniferous ammonium molybdate in pregnant guinea feedstuffs poisoning in goats-variation of pigs and their offspring. Research in Veteri­ selenium contents in wool. blood and tissues. nary Science, 55, 224-230. Acta Zoonutrimenta Sinica, 5, No. 164. Humphries, W.R., Morrice, P.c. and Bremner, I. Howell, J.McC. 1961. Polioencephalomalacia in 1988. A convenient method for the treatment calves. The Veterinary Record, 73, 1165- of chronic copper poisoning in using 1168. subcutaneous ammonium tetrathiomolyb­ -1983. Toxicity problems associated with trace date. The Veterinary Record, 123, 51-53. elements in domestic animals. In: Suttle, N.F., Ishmael, J., Gopinath, C. and Howell, J.McC. Gunn, R.G., Alien, W.M., Linklater, K.A and 1971. Studies with copper calcium EDTA Wiener, G., ed., Trace Elements in Animal acute toxicity in housed sheep. Journal of Production and Veterinary Practice, Occa- Comparative Pathology, 81,279-290.

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