Salt and Trace Minerals for Livestock, Poultry and Other Animals
TRACE MINERAL ANTAGONISTS
Mineral deficiencies may be characterized as primary or secondary depending on the cause of their development. Primary mineral deficiencies are caused by diets that are naturally deficient in one or more minerals. These deficiencies are corrected by the addition of one or more minerals to the diet. Secondary mineral deficiencies are caused by the consumption of one or more mineral antagonist that prevents the absorption or metabolism of another mineral. Simply measuring mineral concentration in the diet may not reveal the source of the problem because all minerals are at or above the requirement. In addition antagonistic mineral concentrations may only be present during certain growing seasons and not create deficiency problems until months later.
Copper is a perfect example of where deficiencies are often the result of antagonistic concentrations of other minerals. Sulfur, molybdenum and iron are three minerals that can readily inhibit copper absorption. High sulfur intakes can result from sulfur in both the feed and water. The increased use of ammonium sulfate fertilizers can increase forage sulfur concentrations to the point that copper deficiency becomes a problem. Florida researchers (329) reported liver copper concentrations of 204, 137, and 72 ppm for cows grazing pastures with no fertilizer, ammonium nitrate, and ammonium sulfate, respectively. Liver copper concentration less than 75 ppm reflect a copper deficiency. Over three years, the forage samples from the ammonium sulfate fertilized pastures average 0.50%. Due to the high sulfur, cows in this study did not respond to a salt-trace mineral mix containing 0.25% copper.
Molybdenum combined with sulfur interferes with copper metabolism through the formation of thiomolybdates in the rumen (147). Suttle (330) showed that increasing dietary sulfur from 0.10 to 0.40% in the presence of molybdenum, increased the copper requirement 50%.
Iron is the second most common trace metal on earth and can be present in high concentrations in both feed and water. The maximum tolerable concentration of iron in cattle diets is 1000 ppm, but dietary concentration as low as 250 ppm have been linked to copper deficiency (278). Exactly how iron prevents copper absorption is poorly understood. One theory involves the disassociation of ferrous sulfide complexes in the acid pH of the abomasum. The free sulfide then binds with copper to form and insoluble copper-sulfide complex.
Many other antagonistic
relationships exist between different minerals. For examples, the antagonists
for zinc include iron, copper, and calcium. Iron, potassium and magnesium are
potentially antagonistic to manganese.
LITERATURE REFERENCES
Copyright: 2006