Zinc Nutrition of Cattle: A Review

Zinc is an essential nutrient for animals, functioning largely or entirely in enzyme systems and being involved in protein synthesis, carbohydrate metabolism, and many other biochemical reactions. A severe zinc deficiency causes numerous pathological changes, including skin parakeratosis, reduced or cessation of growth, general debility, lethargy, and increased susceptibility to infection. However, the mechanism and routes by which specific enzymatic changes are responsible for the serious pathological alterations caused by the deficiency have not been elucidated. Recovery of calves from a severe zinc deficiency is rapid and dramatic. In studies involving special and purified diets, approximately 9 ppm of zinc were adequate for normal health and performance of calves. However, in a few instances, 20 to 40 ppm zinc in practical diets were not sufficient for optimum performance, but in others, such levels were adequate. Logical biological theories are presented for these differences, but proof is lacking. Cattle have a relatively high