Mineral Deficiencies in Florida and Supplementation Considerations
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Mineral Deficiencies in Florida and Supplementation Considerations Lee R. McDowell and Mark E. Tiffany Department of Animal Science University of Florida, Gainesville Summary than 100%, to increase growth rates from 10% to 25%, and to reduce mortality significantly Mineral deficiencies have been and continue to (McDowell, 1992; 1997). be severe detriments to beef cattle production in Florida. Historically, Florida cattle have suffered The first United States reports of Cu or Co from deficiencies of P, Ca, Na, Mg, Co, Cu, Zn, deficiency in grazing cattle originated in Florida and toxicities of F and Mo. In more recent years Se (Becker et al., 1965). Nutritional anemia or “salt deficiency, as evidenced by white muscle disease sick” in cattle, later established as a deficiency of and a “buckling” condition, has been widespread. Fe, Cu and Co, was noted as early as 1872 (Becker Evaluating 15 data sets of Florida forages et al., 1965). Prior to the 1950s, Florida’s nutri- (predominately bahiagrass), the minerals most de- tional deficiencies, as evidenced by low forage ficient were P, Na, Cu, Se and Zn, with Ca, Mg and and(or) animal tissue concentration or decreased Co found to be borderline-to-deficient depending on performance, had been established for Ca, P, Co, location, season, forage species, and year. As a Cu, Na, Mg, and Fe. In more recent years the low-cost insurance measure to provide adequate problems of Se and Zn deficiency for ruminants mineral nutrition, a modified “complete” mineral have been observed. Zinc deficiency was evidenced supplement should be available free-choice. The by hair loss and skin lesions. Throughout the state major disadvantage to free-choice minerals is lack of Florida, Se is severely deficient on the basis of of uniform consumption by animals. Factors soil, forage, blood, and liver analysis, as well as influencing consumption of mineral mixtures white muscle disease (WMD). White muscle include the following: disease is characterized by generalized weakness, (1) soil fertility and forage type stiffness and muscle deterioration, with affected (2) season of year animals having difficulty standing. Calves with (3) available energy and protein WMD have chalky white striations, degeneration and necrosis in the skeletal muscles and heart. In (4) individual requirements calves the tongue musculature may be affected, (5) salt content of water preventing suckling. Often death occurs suddenly (6) palatability of mineral mixture from heart failure as a result of severe damage to (7) availability of fresh minerals heart muscle. In milder cases (in which calves are (8) physical form of minerals stiff and have difficulty standing) dramatic, rapid improvement can result from Se–vitamin E Introduction injections. Mineral deficiencies or imbalances in soils and Since the mid 1980s WMD has been most forages have long been held responsible for low frequently exhibited as “buckling;” feeder calves production and reproduction problems of Florida come off the truck or out of the processing chute beef cattle (Cunha et al., 1964; Becker et al., 1965; with weakness of rear legs, buckling of fetlocks McDowell, 1997). Research from other warm and, frequently, generalized shaking or quivering of climate regions has shown mineral supplementation muscles. Many calves become progressively worse to increase calving percentages by 20% to more until they are unable to rise and may appear to be McDowell and Tiffany paralyzed. Death loss is high among severe cases, National Research Council (NRC) requirements are and calves with excitable temperaments appear to often based on growth performance and quantities be most commonly affected. Post-mortem of a specific mineral sufficient to prevent clinical examination of affected calves reveals pale, chalky signs of a deficiency. Selenium, Cu, Zn, and Co streaks in muscles of the hamstring and back. The deficiencies have been shown to alter various heart, rib muscles, and diaphragm can also be components of the immune system. Selenium affected. supplementation has decreased mortality rates in ruminants fed diets low in Se when clinical defi- As a consequence of modern farming systems, ciency signs, such as muscular dystrophy, were not acute deficiencies of most minerals for beef cattle apparent. A 2-year study with beef cows and calves have been reduced in Florida. However subclinical consuming pasture and corn silage marginally deficiencies, which lower growth and reproduction deficient in Se (.03 to .05ppm) indicated that rates, are affecting beef cattle production. bimonthly Se–vitamin E injections reduced calf Inadequate minerals can affect the immune re- death losses (4.2 versus 15.3%) from birth to sponse and can increase rates of diarrhea and weaning (Spears et al., 1986). Most of the deaths respiratory conditions. Florida has a 10 to 11% were attributed to diarrhea and subsequent unthrift- lower calving percentage than the U.S. average. In- iness. adequate mineral nutrition for Florida beef cattle is certainly one reason for less-than-optimum For grazing livestock, P is the mineral most reproductive rates. This paper will discuss forage likely to be deficient. There are differences of opin- mineral concentrations in Florida as they relate to ion as to P requirements of beef cattle. Phos- deficiencies and free-choice mineral supplementa- phorous requirements recommended by the NRC tion for cattle. may be too high for grazing beef cattle. In Utah, no difference in average weight gains (.45 kg/day), Mineral Requirements for Cattle feed efficiency, or appetite were observed between Hereford heifers fed for 2 years on a diet containing Estimated mineral requirements and factors af- .14% P (66% of NRC recommendation) and fecting the mineral content of forages and bio- comparable heifers receiving the same diet availability of inorganic and organic (e.g., chelates) supplemented with monosodium phosphate to mineral supplements are reported elsewhere provide a total of .36% P. After 8 months on a (McDowell et al., 1992; 1997). Mineral require- .09% P diet, however, some appetite reduction and ments are highly dependent on the level of produc- decreased bone density were observed. On the tivity. Increased growth rates and milk production contrary, studies from Florida demonstrated that will greatly increase mineral requirements. Mineral .12 to .13% P was inadequate for growing Angus deficiencies that are marginal under low levels of heifers in a 525- to 772-day experiment. Animals production become more severe with increased receiving the low P diet had lower gains (205 levels of production, and previously unsuspected versus 257 kg), exhibited pica, and had bone nutritional deficiency signs usually occur as demineralization (Williams et al., 1991). production levels increase. Adequate intake of forages by grazing rumi- The criterion of adequacy is important; there is nants is essential to meet mineral requirements. reason to suggest that mineral requirements for Factors that greatly reduce forage intake, such as optimal immune responsiveness and disease resist- low protein content (<7.0%) and increased degree ance are greater than requirements for growth. of lignification, likewise reduce total minerals 128 MANAGING NUTRITION & FORAGES TO IMPROVE PRODUCTIVITY & PROFITABILITY Mineral Deficiencies in Florida and Supplementation Considerations consumed. Mineral supplementation is much less likely to be deficient and need supplementation important for cattle if energy–protein requirements were P, Na, Cu, Se, and Zn (and at this location are inadequate. But, when energy and protein also Co.) Iron was also relatively low. supplies are adequate, livestock gain weight rapidly, resulting in high mineral requirements. It is Free-Choice Mineral Supplements therefore uneconomical to provide mineral supplements to grazing cattle if the main nutrients Free-Choice (Free-access) they are lacking are energy and(or) protein. Mineral Supplementation Florida Mineral Deficiencies Voluntary consumption of individual minerals or mineral mixtures by animals is referred to as Table 1 (macrominerals) and Table 2 (trace free-choice or free-access feeding. This practice of minerals) illustrate forage mineral concentrations feeding minerals free-choice to ruminants has been from 15 data sets from different regions in Florida, used for many years to supply needed minerals, but compared to critical concentrations. Data are is often based on the erroneous assumption that the presented by season, representing spring–summer animal knows which minerals are needed and how (wet) and fall (dry). In all of the studies, the miner- much of each mineral is required. Animals not als most consistently deficient in the majority of consuming concentrates are less likely to receive an forages were P, Na, Cu, Se, and Zn. The minerals adequate mineral supply; free-choice minerals are Ca, Mg and Co were borderline-to-deficient in much less palatable than concentrates and are often some studies, depending on location, season, for- consumed irregularly. Intakes of free-choice age species and year. Minerals not deficient were mineral mixtures by grazing cattle are highly K, Fe, and Mn. Molybdenum was not reported to variable and not related to mineral requirements. be in excess for the present studies. However, a Factors that affect the consumption of mineral number of Florida studies have shown that excess mixtures have been listed by Cunha et al. (1964) Mo in high-pH soils (normally, organic soils) inter- and McDowell (1992), and