Trace Mineral Nutrition-What is Important and Where do Organic Trace Minerals Fit in?

Transcription

1 Trace Mineral Nutrition-What is Important and Where do Organic Trace Minerals Fit in? J. W. Spears Department of Animal Science North Carolina State University Corresponding author: Introduction One or more trace minerals are required for the normal functioning of essentially all biochemical processes in the body. Deficiencies of essential trace minerals, depending on the severity, can result in clinical or subclinical deficiency signs. Dietary requirements for many trace minerals are affected by their bioavailability, and antagonist that reduce bioavailability. The action of trace minerals are dose dependent and even essential trace minerals can produce toxic effects when consumed at high concentrations (Figure 1). Toxic effects of trace minerals can be subtle with no clinical signs. For example, Olson et al. (1999) reported that supplementing beef cows with zinc, copper, manganese, and cobalt at concentrations at least twice the NRC requirement, following calving, reduced pregnancy rates in beef cows. On the other extreme, high levels of certain trace minerals, such as copper and selenium, can result in death. Figure 1. Relationship between trace mineral intake and animal responses

2 Trace Mineral Functions and Bioavailability Cobalt The only known function of cobalt relates to its role as a component of vitamin B 12. Ruminal microorganisms are able to synthesize vitamin B 12 from dietary cobalt. The vitamin B 12 -dependent enzyme methylmalonyl CoA mutase is involved in the metabolism of propionate to succinate in the liver. A second vitamin B 12 -dependent enzyme (methionine synthase) is important in the recycling of methionine following transfer of its methyl group and in the maintenance of tissue folate concentrations. A lack of dietary cobalt for vitamin B 12 synthesis by rumen microorganisms can also alter ruminal fermentation. Low dietary cobalt in high concentrate finishing diets reduces molar proportion of ruminal propionate (Tiffany et al., 2003; Tiffany and Spears, 2005). Studies in growing and finishing cattle suggest that dietary cobalt requirements are higher than the 0.10 mg/kg diet recommended by the NRC (Schwarz et al., 2000; Tiffany et al., 2003). Depending on the criteria used, estimates of cobalt requirements have ranged from 0.12 to 0.26 mg/kg diet. A recent study in dairy cows indicated that cobalt supplementation of prepartum and postpartum diets containing 0.15 to 0.19 mg Co/kg did not affect milk production, intake or serum vitamin B 12 concentrations (Kincaid and Socha, 2007). In addition to cobalt, other dietary factors may affect vitamin B 12 production by ruminal microorganisms. Research in finishing cattle suggests that ruminal synthesis of vitamin B 12 is lower in cattle fed barley-based diets compared to corn-based diets (Tiffany and Spears, 2005). Copper Copper is a component of a number of enzymes including lysyl oxidase, superoxide dismutase, tyrosinase, ceruloplasmin and cytochrome oxidase. These enzymes are important in the structural integrity of collagen and elastin, detoxification of superoxide radicals, pigmentation, iron transport, and energy metabolism. Sulfur and molybdenum are potent copper antagonists and can greatly increase copper requirements. Sulfide is produced in the rumen via reduction of sulfate and degradation of sulfur amino acids. Sulfide and molybdate interact in the rumen environment, when dietary molybdenum and sulfur are high, to form thiomolybdates (Spears, 2003). Tri and tetrathiomolybdates can form stable insoluble complexes with copper that are not absorbed. Certain thiomolybdates that are not bound to copper can be absorbed and cause excretion of stored copper from the liver or removal of copper from metalloenzymes (Suttle, 1991). Independent of dietary molybdenum, sulfur reduces copper absorption probably through the formation of insoluble copper sulfide in the gut. High dietary iron, when provided in an available form also reduces copper status in cattle (Mullis et al., 2003).

3 Iron Iron plays a vital role in oxygen transport in the blood as a component of hemoglobin and in oxygen storage and transport in muscle as a component of myoglobin. A number of cytochromes and iron-sulfur proteins involved in the electron transport chain also contain iron as an integral component. In addition several enzymes either contain iron or are activated by iron. Most practical diets are more than adequate in iron, and iron deficiency is unlikely in cattle unless parasite infestations or diseases exist that cause chronic blood loss. Factors affecting bioavailability of iron in ruminants have received little attention in ruminants because of the abundance of iron in ruminant diets. Manganese Manganese is an integral component on the enzymes, arginase, superoxide dismutase found in the mitochondria, and pyruvate carboxylase. In addition, a number of enzymes can be activated by manganese. Of the enzymes that can be activated by manganese only the glycosyltransferases are known to specifically require manganese. Glycosyltransferases are involved in the synthesis of proteoglycans, and thus are required for normal formation of skeletal cartilage. Recent studies with growing and finishing cattle (Legleiter et al., 2005), and growing heifers (Hansen et al., 2006a) suggests that manganese requirements do not exceed 16 mg Mn/kg diet. However, this level of manganese was found not to be sufficient for normal fetal development in gestating heifers (Hansen et al., 2006b). When heifers were continued on the control diet, containing 16 mg Mn/kg, during gestation signs of manganese deficiency were observed in some of their calves at birth. Deficiency signs observed included dwarfism and superior brachygnathism. None of these signs were noted in calves born to dams supplemented with 50 mg Mn/kg. Factors that may reduce manganese bioavailability, and thus increase dietary manganese requirements are not clearly defined. High dietary iron may reduce manganese bioavailability in certain instances. Possible effects of iron on manganese metabolism will be discussed in more details in the next section of this paper. Limited evidence suggests that high dietary calcium and phosphorus may reduce manganese bioavailability (Hidiroglou, 1979). Selenium Selenium functions in the antioxidant system as a component of a family of glutathione peroxidase enzymes. These enzymes prevent cellular damage by destroying hydrogen peroxide and lipid hydroperoxides. Selenium also is involved in the deiodination of thyroxine (T 4 ) to the more metabolically active triiodothyronine (T 3 ) in tissues. The immune system is adversely affected by selenium deficiency, and it is well

4 documented that selenium deficiency increases the incidence of mastitis and retained placenta in dairy cows. Sulfur and selenium have similar chemical properties and increasing dietary sulfur reduces the absorption of selenium (Ivancic and Weiss, 2001). There is also evidence that selenium is less bioavailable in legume hay than in grass hay or concentrates (Spears, 2003). Selenomethionine, which is the major form of selenium found naturally in feedstuffs and in selenized yeast, is more bioavailable in cattle than sodium selenite (Pehrson et al., 1989). Zinc Zinc is an essential component of over 70 enzymes found in mammalian tissues. Enzymes that require zinc are involved in protein, nucleic acid, carbohydrate, and lipid metabolism. Zinc is also important for normal development and functioning of the immune system, in cell membrane stability, and gene expression. Responses of cattle to zinc supplementation of practical diets have been highly variable, suggesting that dietary factors affect zinc bioavailability. However, dietary factors that may affect zinc bioavailability in ruminants are not well defined. Some studies would suggest that high dietary calcium reduces zinc status in cattle (Spears, 2003). Possible Consequences of High Dietary Trace Mineral Concentrations It is obviously important to supply adequate quantities of essential trace minerals to meet nutritional requirements in order to maximize productivity and health in cattle. However, excessive supplementation of trace minerals or use of feedstuffs naturally high in certain trace minerals can create mineral imbalances or produce other toxic effects that negatively affect animal performance. Supplementing zinc and copper in high concentrations relative to requirements may also lead to environmental concerns due to run-off and land application of waste containing high levels of these metals. Copper and zinc imports and exports were recently measured in six dairies in Idaho over a 1-year period (Hristov et al., 2007). Imports far exceeded exports resulting in whole-farm surpluses for both minerals. They concluded that reducing dietary concentrations of copper and zinc was the most efficient way of reducing excretion and whole-farm surpluses of these minerals. Most trace minerals are generally supplemented in dairy diets at levels equal to or above NRC recommendations. With iodine, cobalt, and selenium this is probably a good practice because of their low requirement, the expense of analyzing feedstuffs for these minerals, and the minimal interactions expected between these minerals and other minerals. However, numerous interactions can occur between iron, copper, zinc, and manganese. The balance between dietary concentrations of these minerals, especially bioavailable concentrations, is an important factor affecting mineral utilization and thus animal requirements. With these trace minerals we should consider their concentrations

5 in major dietary ingredients. Variation in the mineral content of feedstuffs presents a problem when formulating mineral supplements. Forages vary considerably in mineral concentrations. However, much less variation in mineral content is usually found in cereal grains and oilseed meals. Supplementation of trace minerals above requirements is often practiced as a safety margin, to prevent any likelihood of deficiencies. Providing a certain level of safety is sound, but the question becomes at what magnitude relative to requirements should safety levels be provided. If trace minerals are present in the diet in a bioavailable form, homeostatic control mechanisms in the animal serve to prevent deficiencies. It has long been recognized that homeostatic mechanisms alter absorption and/or excretion of essential trace minerals in response to changes in the amount of the mineral consumed or required, resulting in tissue concentrations of most minerals being maintained within a fairly narrow range (Miller, 1975). Transporters have been characterized in recent years for zinc, copper, and iron that are involved in cellular transport and assimilation of the metals by intestine and other tissues. Many of these transporters are down regulated when trace minerals are fed in excess of requirements and up regulated when the mineral is fed at low or marginal levels relative to requirements. Changes in the efficiency of mineral absorption or post absorptive excretion serves to protect against trace mineral deficiencies as well as toxicities. However, homeostatic control mechanisms can be overwhelmed when extremely high concentrations of minerals are fed resulting in subclinical or clinical signs of toxicosis. High Dietary Iron As mentioned previously, iron deficiency is unlikely in cattle because of the high concentrations of iron commonly found in feedstuffs. It is not uncommon for ruminant diets to exceed iron requirements by 5-fold or greater. Some feedstuffs that are likely to be high in iron are shown in Table 1. Hays and silages are highly variable in iron content as indicated by their high standard deviations. Many by-product feeds that are fairly high in iron vary less in their iron content. Use of phosphate supplements also increases iron intake by cattle, as commercial dicalcium and defluorinated phosphates contain approximately 10,000 mg Fe/kg. Cattle grazing pastures may be exposed to high iron through forage and/or soil ingestion. High dietary iron, when provided in a form such as ferrous sulfate, that is highly bioavailable, has been associated with reduced performance, elevated liver and spleen iron concentrations, and decreased copper status (Standish et al., 1969; Mullis et al., 2003). Iron absorption is well regulated, but exposure to high dietary iron may overwhelm homeostatic control mechanisms resulting in iron accumulation in tissues, especially the liver and spleen. Iron that is not bound tightly to ligands in the body acts as a pro-oxidant and causes oxidative damage to tissues. At normal tissue iron concentrations the oxidant properties of iron are minimal due to iron being bound to proteins. However, with elevated iron in the body there is a greater likelihood of free iron existing in certain tissues and causing increased production of free radicals that may lead to tissue damage. Based on field observations, Pitzer (1994) reported that high iron

6 in feed or water was associated with impaired reproductive performance and increased incidence of uterine infections. He attributed these adverse effects to the pro-oxidant effects of iron. A number of studies have indicated that high dietary iron is a potent copper antagonist. The addition of as little as 250 mg Fe/kg diet (from ferrous carbonate) reduced liver copper concentrations in calves (Bremner et al., 1987). High iron may also reduced absorption of manganese. It has been demonstrated in rodents that high dietary iron down regulates divalent metal transporter (DMT1), the major transport protein involved in transport of iron into intestinal cells (Miret et al., 2003). Although DMT1 is regulated by iron, it also transports other metals including manganese and copper (Miret et al., 2003). Therefore, high dietary iron may reduce absorption of manganese and copper by competition for DMT1 as well as reducing the actual amount of transport protein. Little is known regarding bioavailability of iron naturally found in feedstuffs. High dietary iron may not cause adverse effects on animal performance or health if the iron present in the diet is of low bioavailability. However, if iron present in feeds is fairly bioavailable, adverse effects of high iron are more likely to be seen. When high iron concentrations are detected in forages it is unclear how much of the iron is naturally present in the forage and how much of the iron is due to soil contamination. In most soil types iron is extremely high. Iron in soil is generally of low solubility and probably very poorly absorbed when ingested by cattle. Acid conditions occurring during the fermentation of silage or haylage may result in soil iron being much more bioavailable when consumed by cattle. When 1 or 5% soil from different soil types was added to corn silage prior to ensiling the amount of iron in the silage that was water soluble increased by 18 to 84 fold compared to control silage with no soil added (Hansen and Spears, unpublished). When the same levels of soil were added to silage after fermentation water soluble concentrations of iron only increased 1.6 to 2.2 fold relative to control silage. This suggests that iron bioavailability from soil may be greatly increased by ensiling. Much of the iron in soybeans has been shown to be present in the form of ferritin (Theil, 2004). This is the same ferritin protein that stores iron in the liver of humans and animals. Recently, ferritin from soybeans was found to be absorbed as well in humans as ferrous sulfate (Lonnerdal et al., 2006). If ferritin is a major form of iron in other legumes, this may represent a highly bioavailable form of iron in ruminants. Based on research in chicks (Henry et al., 1992) and swine (Kornegay, 1972), iron from feed grade phosphate sources is 48 to 67% as bioavailable as iron from ferrous sulfate.

7 Table 1. Iron concentrations in feedstuffs Mean SD By-product feeds a Almond hulls Beet pulp Brewers grains Canola meal Corn gluten feed Distillers grains Cane molasses Safflower meal Soybean hulls Wheat meal run Other feedstuffs b Alfalfa Corn silage Grass hay Grass silage Legume hay Legume silage Sorghum grain silage Sorghum Sudan hay Sorghum Sudan silage Soybean meal a From DePeters et al., From NRC (2001). Organic Trace Minerals Organic trace minerals are complexed or chelated to organic ligands (amino acids or polysaccharides). In theory the chemical bonds formed between the metal and ligand(s) should allow organic trace minerals to resist many of the interactions encountered by inorganic trace mineral sources. Organic sources of trace minerals have been found to be more bioavailable than inorganic sources in some studies (Ward et al., 1996; Hansen et al., 2008). Using organic trace minerals to replace at least a portion of supplemental inorganic trace minerals should allow nutritionist to reduce the overall inclusion rate of trace minerals and still provide a reasonable safety margin. Reducing the inclusion rate in concentrated cattle operations also will reduce the environmental impact related to excretion of trace minerals such as zinc and copper in waste.

8 Responses of dairy and beef cattle to supplementation with organic trace minerals have been variable. A number of factors such as the level and bioavailability of trace minerals in feedstuffs can affect whether dairy or beef cattle respond to organic trace minerals supplementation. In this paper I will emphasize studies where positive responses have been observed. Replacing a portion of the inorganic trace minerals with chelated or complexed trace minerals has improved reproduction in a number of dairy studies (Uchida et al., 2001; Ballantine et al., 2002; Nocek and Patton, 2002). In one study, over 500 cows received total mixed rations supplemented with either inorganic trace minerals or a combination of inorganic and proteinate trace minerals (Nocek and Patton, 2002). Cows were fed their respective mineral treatment from 60 days prepartum until 150 days postpartum. Trace minerals were added in both treatments to provide 120% of the NRC requirement. In the chelated treatment, 50% of the supplemental zinc, manganese, and copper were supplied from proteinate chelates. Reproductive performance is shown in Table 2. Days to first heat and days to first breeding were lower for cows fed chelated trace minerals. Days open, for cows confirmed pregnant by 150 days in milk, were 7 days less for the chelated treatment group. A recent study (Nocek et al., 2006) indicated that reproductive performance was greater in dairy cows supplemented with a combination of inorganic and organic trace minerals compared to cows supplemented exclusively with inorganic or complexed minerals. Milk production has also been increased by using organic trace minerals in some studies (Ballantine et al., 2002; Nocek and Patton, 2002: Nocek et al., 2006). In beef cows adding trace mineral proteinates (Tiffany et al., 2001) or complexes (Stanton et al., 2001) to free choice mineral supplements has improved reproduction, especially AI pregnancy rates. Finishing steers supplemented with zinc proteinate tended to gain faster and more efficiently than steers receiving zinc oxide (Spears and Kegley, 2002). Hot carcass weights and dressing percentages were also high in steers supplemented with zinc proteinate. Malcolm-Callis et al (2000) reported no differences in performance of finishing cattle supplemented with zinc sulfate, zinc amino acid complex or a zinc polysaccharide complex. However, subcutaneous fat thickness was higher in steers fed either organic zinc source compared to zinc sulfate. Table 2. Effect of trace mineral chelates on reproductive performance of Holstein cows a Treatment Item Control Chelates P value All cows n Days to first heat Days to first breeding Cows confirmed pregnant b n Days to first heat Days to first breeding Days open

9 Services/conception NS a From Nocek and Patton, b Cows confirmed pregnant by 150 days in milk. REFERENCES Ballantine, H. T., M. T. Socha, D. J. Tomlinson, A.B. Johnson, A. S. Fielding, J. K. Shearer, and S. R. Van Amstel Effects of feeding complexed zinc, manganese, copper, and cobalt to late gestation and lactating dairy cows on claw integrity, reproduction, and lactation performance. Prof. Anim. Sci. 18: Bremner, I., W. R. Humphries, M. Phillippo, M. J. Walker, and P. C. Morrice Iron-induced copper deficiency in calves: dose-response relationships and interaction with molybdenum and sulfur. Anim. Prod. 45: DePeters, E. J., J. G. Fadel, M. J. Arana, N. Ohansesian, M. A. Etchebarne, C. A. Hamilton, R. G. Hinders, M. D. Maloney, C. A. Old, T. J. Riordan, H. Perez-Monti, and J. W. Pareas Variability in the chemical composition of seventeen selected by-product feedstuffs used by the California dairy industry. Prof. Anim. Sci. 16: Hansen, S. L., J. W. Spears, C. S. Whisnant, and K. E. Lloyd. 2006a. Growth, reproductive performance, and manganese status of beef heifers fed varying concentrations of manganese. J. Anim. Sci. 84: Hansen, S. L., J. W. Spears, K. E. Lloyd, and C. S. Whisnant. 2006b. Feeding a low manganese diet to heifers during gestation impairs fetal growth and development. J. Dairy Sci. 89: Hansen, S. L., P. Schlegel, L. R. Legleiter, K. E. Lloyd, and J. W. Spears Bioavailability of copper from copper glycinate in steers fed high dietary sulfur and molybdenum. J. Anim. Sci. 86: Henry, P. R., C. B. Ammerman, R. D. Miles, and R. C. Littell Relative bioavailability of iron in feed grade phosphates for chicks. J. Anim. Sci. 70(Suppl. 1):228. Hidiroglou, M Manganese in ruminant nutrition. Can. J. Anim. Sci. 59: Hristov, A. N., W. Hazen, and J. W. Ellsworth Efficiency of use of imported magnesium, sulfur, copper, and zinc on Idaho dairy farms. J. Dairy Sci. 90: Ivancic, J., and W. P. Weiss Effect of dietary sulfur and selenium concentrations on selenium balance of lactating Holstein cows. J. Dairy Sci. 84:

10 Kincaid, R. L., and M. T. Socha Effect of cobalt supplementation during late gestation and early lactation on milk and serum measures. J. Dairy Sci. 99: Kornegay, E. T Availability of iron contained in defluorinated phosphate. J. Anim. Sci. 34: Legleiter, L. R., J. W. Spears, and K. E. Lloyd Influence of dietary manganese on performance lipid metabolism, and carcass composition of growing and finishing steers. J. Anim. Sci. 83: Lonnerdal, B., A. Bryant, X. Liu, and E. C. Theil Iron absorption from soybean ferritin in nonanemic women. Am. J. Clin. Nutr. 83: Malcolm-Callis, K. J., G. C. Duff, S. A. Gunter, E. B. Kegley, and D. A. Vermeire Effects of supplemental zinc concentration and source on performance carcass characteristics, and serum values in finishing beef steers. J. Anim. Sci. 78: Miller, W. J New concepts and developments in metabolism and homeostasis of inorganic elements in dairy cattle. A review. J. Dairy Sci. 58: Miret, S., R. J. Simpson, and A. T. McKie Physiology and molecular biology of dietary iron absorption. Annu. Rev. Nutr. 23: Mullis, L. A., J. W. Spears, and R. L. McCraw Effect of breed (Angus vs Simmental) and copper and zinc source on mineral status of steers fed high dietary iron. J. Anim. Sci. 81: National Research Council Nutrient Requirements of Dairy Cattle. 7 th ed. National Academy Press, Washington, D.C. Nocek, J. E. and R. S. Patton Effect of chelated trace mineral supplementation for inorganic sources on production and health of Holstein cows. J. Dairy Sci. 85(Suppl. 1):107. Nocek, J. E., M. T. Socha, and D. J. Tomlinson The effect of trace mineral fortification level and source on performance of dairy cattle. J. Dairy Sci. 89: Olson, P. A., D. R. Brink, D. T. Hickok, M. P. Carlson, N. R. Schneider, G. H. Deutscher, D. C. Adams, D. J. Colburn, and A. B. Johnson Effects of supplementation of organic and inorganic combination of copper, cobalt, manganese, and zinc above nutrient requirement levels on postpartum two-year-old cows. J. Anim. Sci. 77:

11 Pehrson, B., M. Knutsson, and M. Gyllensward Glutathione peroxidase activity in heifers fed diets supplemented with organic and inorganic selenium compounds. Swedish J. Agric. Res. 19: Pitzer, D The trouble with iron. Feed International. August, pages Schwarz, F. J., M. Kirchgessner, and G. I. Stangl Cobalt requirements of beef cattle- feed intake and growth at different levels of cobalt supply. J. Anim. Physiol. Anim. Nutr. 83: Spears, J. W Trace mineral bioavailability in ruminants. J. Nutr. 133:1506S- 1509S. Spears, J. W., and E. B. Kegley Effect of zinc source (zinc oxide vs zinc proteinate) and level on performance, carcass characteristics, and immune response of growing and finishing steers. J. Anim. Sci. 80: Standish, J. F., C. B. Ammerman, C. F. Simpson, F. C. Neal, and A. Z. Palmer Influence of graded levels of dietary iron, as ferrous sulfate, on performance and tissue mineral composition of steers. J. Anim. Sci. 29: Stanton, T. L., J. C. Whittier, T. W. Geary, C. V. Kimberling, and A. B. Johnson Effects of trace mineral supplementation on cow-calf performance, reproduction, and immune function. Prof. Anim. Sci. 16: Tiffany, M. E., and J. W. Spears Differential responses to dietary cobalt in finishing steers fed corn-versus barley-based diets. J. Anim. Sci. 83: Tiffany, M. E., J. W. Spears, L. Xi, and J. Horton Influence of dietary cobalt source and concentration on performance, vitamin B 12 status, and ruminal plasma metabolites in growing and finishing steers. J. Anim. Sci. 81: Theil, E. C Iron, ferritin and nutrition. Annu. Rev. Nutr. 24: Uchida, K., P. Mandebvu, C. S. Ballard, C. J. Sniffen, and M. P. Carter Effect of feeding a combination of zinc, manganese and copper amino acid complexes, and cobalt glucoheptonate on performance of early lactation high producing dairy cows. Ward, J. D., J. W. Spears, and E. B. Kegley Bioavailability of copper proteinate and copper carbonate relative to copper sulfate in cattle. J. Dairy Sci. 79: