Trace elements in cattle nutrition Christian Punz Product Manager Nutritional Products Christian Punz Product Manager Nutritional Products Trace elements in cattle nutrition The importance of trace elements in livestock nutrition is undisputed. As the name implies, even small amounts of these elements have large and diverse effects on the animal organism. The function of enzymes and hormones is essentially linked to trace elements. This key role in metabolism cannot be replaced by other kinds of nutrients, that’s why we call them „essential“ (irreplaceable) trace elements. or cattle, copper, zinc, manganese, cobalt, elements are absorbed into the small intestine via the iodine and selenium are among the most amino acid–peptide way. Th e most effi cient absorption important and are usually added to various is when trace elements are bound to single amino ac- supplementary feed. Since iron has a decisive ids. Trace elements bound in chelate form are a mixture infl uence on the interactions between the ele- of all naturally occurring amino acids and are absorbed ments, it will be discussed in later chapters as well. through the diff erent amino acids absorption mecha- FRegarding the bioavailability of trace elements from nisms in the body. the feed, there are signifi cant diff erences due to the bind- Th is article will provide guidance on the basic func- ing form of the elements. In general, two main binding tion of trace elements in ruminants, demonstrate the dif- types can be distinguished: ference in bioavailability of diff erent binding forms and • Inorganic bound trace elements (sulfates, oxides, show practical eff ects in examples from cattle. chlorides, carbonates, …) • Organic bound trace elements (chelates, protein- What are trace elements? ates, glycinates, polysaccharides, fatty acids, methi- Trace elements are defi ned by their extremely low onine-analogues, …) concentrations in the body, such as less than 50 mg of iron per kg of tissue. Based on this, daily animal require- Inorganic bound trace elements are likely to have ments of trace elements are in the milligram range as specifi c interactions and must be bound to transporters well. Needs for trace elements are determined by nutri- to be absorbed in the metabolism. Organic bound trace ent requirement models and nutrient response models. 2 Biological functions of trace elements Iron Manganese Iron is a part of hemoglobin, the pigment of red Manganese is mainly stored in the bone, liver, kidney blood cells and myoglobin, the muscle pigment that and pancreas. It works as an enzyme activator and is is necessary for their formation. In addition, iron is crucial for energy-, protein- and fat metabolism. Fur- responsible for oxygen storage and oxygen transport thermore, it has important enzymatic functions in cell in the body. As an enzyme component iron plays an protection. important role in energy metabolism as well as in the Deficiencies in manganese are reflected in reduced anti-oxidative system (immune system). growth, skeletal deformities, poor fertility and birth Iron deficiency is not common in dairy cows because defects in newborn calves. many feedstuffs (mainly forage) contain iron in suf- ficient amounts. However, it may lead to deficiency Iodine symptoms in calves supplemented with whole milk. Iodine is located in the thyroid glands and is responsi- Deficiency symptoms manifest themselves in the form ble for the formation of thyroid hormones (T3 and T4 of anemia, poor immunity and growth. In fact that hormone). These hormones in turn take over import- iron is much more common than other trace elements, ant control processes in the energy metabolism and are iron excess can lead to poor absorption for copper and thus particularly important for growth, fertility and manganese. milk yield. Iodine deficiency can be detected by an enlarged thy- Copper roid gland and poor milk production. Copper is mainly stored in the liver and is an enzyme component that is part of many essential metabolic Cobalt processes. As an enzyme activator, copper provides Cobalt serves as a central atom of Vitamin B12 (Co- strong bones and joints and is heavily involved in the balamin). If ruminants are adequately supplied with utilization of iron and thus the synthesis of hemoglo- Cobalt, they can synthesize their need for Vitamin bin. In addition, the pigmentation of the hair coat is B12 itself in the rumen. Vitamin B12 is necessary for fundamentally influenced by copper levels. Through a functioning energy- (utilization of propionic acid, the promotion of superoxid dismutase, which deac- gluco neogenesis) and protein metabolism (methi- tivates free oxygen radicals, copper is also involved onine formation) in the liver. in cell protection and thereby in a healthy immune A prolonged deficiency in cobalt leads to a decrease in system. feed intake, limited growth and reduced milk yield. Copper deficiency in dairy cows is often reflected in Selenium reduced fertility and poor immunity. Similarly, dis- turbances in pigmentation (“Copper glasses”), anemia Selenium is an essential component of the enzyme and bone fragility may occur. glutathion peroxidase, which deactivates harmful hy- drogen peroxide radicals and is thus crucial in cell pro- Zinc tection. In addition, it supports the effects of Vitamin Beside iron, zinc is the most common trace element. E and vice versa. A slight lack of one element can be As an activator and a component of more than 300 compensated by a higher supply of the other element enzymes and hormones, zinc plays an important role to a certain extent. Moreover, Selenium also regulates in metabolism. In particular, protein biosynthesis and the thyorid hormone metabolism and thus indirectly the regulation of gene activity can be affected by zinc. affects fertility in dairy cows. Zinc is mainly stored in the liver, pancreas, bone, skin Selenium deficiency causes fertility disorders, muscle and hair. dystrophy and weak calves as well as retained placenta Zinc deficiency causes poor growth, loss of appetite, and mastitis in dairy cows. Also a sufficient selenium and a bad feed conversion rate. Due to its crucial supply is important in dry function in defense enzymes (copper-zinc superoxid cows because still births dismutase), zinc deficiency reduces resistance. In dairy or aborts can otherwise cows, zinc deficiency is visible through bad hoof horn occur. quality, reduced fertility and poor udder health. Source: Zinpro Figure 1: „Copper glasses“ caused by copper deficiency 3 Christian Punz Product Manager Nutritional Products They are responsible for specific functions in the organ- trace elements, macro elements or other food sources. ism for certain metabolic processes and must be regu- For example phytate can build complexes with zinc, larly supplied with feed.. An essential function of trace copper, manganese and iron and negatively impair their elements is that they act as an activator and part of many absorption into the body. Crude fibre can block the ab- enzymes. Furthermore they are present in proteins and sorption of metal ions. carry out several tasks in the hormonal system. There- Ca fore, basic functions such as reproduction of dairy cows Te Co depend a lot on the supply of trace elements. Hg Cu Regulation of absorption and excretion Al K For a functioning metabolism, trace elements always I W have to be present at a specific concentration in the tar- get tissue. To avoid an over-concentration and thus the Zn risk of poisoning, the trace element metabolism is strict- Se ly controlled by the homeostatic regulation. This means S that the input and outflow are regulated such that the Cd interior of the body always has the same concentration Mn in different target tissues. The processes of acquisition, Mg storage and excretion of trace elements are overlapping Na and always in a dynamic equilibrium. F Mo Pb Fe As P Interactions of trace elements In the uptake of trace elements, it is always import- Figure 2: Interactions between micro- and ant to consider certain adverse interactions with other macro minerals (Graphic: Punz; Source: Miller, 1979) Table 1: Trace element content of the most important forages and concentrates in Austria. (ÖAG-Futterwerttabellen für das Grundfutter im Alpenraum, Resch et al. 2006; Daten aus dem Futtermittellabor Rosenau 1998-2008) Feed stuff Trace element content (mg/kg DM) Iron Manganese Zinc Copper Forages Grass silage, 1st cut 696 90 50 7.9 Grass silage, 2nd -5th cut 746 103 46 8.7 Corn silage 125 27 38 3.9 Concentrates Barley 64 19.6 32.9 5.4 Corn 40 8.3 26.0 2.5 Triticale 39 39.9 35.7 6.2 Dried beet pulp 605 67.6 27.4 6.0 Wheat 50 39.8 30.3 5.3 Brewers' grain (dried) 195 57 104.1 14.9 Peas 169 18.1 91 14.9 Rape seed extracted 190 76.2 78.9 7.1 Rape seed cake (8-12% fat) - 63.4 63.1 5.5 DDGS (from bioethanol production) 160 75.2 65.0 10.0 Soy bean full fat 103 30.5 51.5 15.8 Soy bean extracted 301 42.0 56.9 18.6 Soy bean extracted HP 303 50.5 59.0 15.9 Sunflower seed extracted (dehulled) 177 33.5 79.1 28.5 Diets rich in calcium, and drinking water or silages Table 2: Recommendations and legal limits for trace elements high in iron can build hardly soluble complexes with in dairy cows copper or manganese and reduce their availability dra- Recommendations Legal limits matically. In the presence of high levels of molybdenum (mg/kg DM) (mg/kg com- plete feed) and sulfates, copper sulfide can occur which is hardly soluble as well and nearly unusable for ruminants. Jeroch et al. NRC 2001 If the diet contains too much sulfur, the uptake of 2008; GfE Selenium in the body is negatively affected.