Zinc regulates over a dozen important enzyme systems involved in metabolism of protein and carbohydrates. Zinc is also required for maintaining responsiveness of the immune system through energy production, protein synthesis, stabilization of membranes against bacterial endotoxins, antioxidant enzyme production and maintenance of lymphocyte replication and antibody production. Virtually every phase of cell growth involves Zn, and a deficiency can impact productivity. For example, zinc serves as an activator of enzymes necessary in steroid genesis, which regulates secretion of gonadal hormones. Zinc is also essential for vitamin A metabolism and both have a synergestic action.
The recommended requirement of zinc is 30 mg Zn/kg diet, a concentration which should satisfy requirements in most situations. Zinc deficiency can adversely affect reproductive processes in females from estrus to parturition. Inadequate Zn levels in gestating cows may result in abortion, fetal mummification, lower birth weight or altered myometrial contractility with prolonged labor. Other effects reported include impaired growth, delayed puberty and decreased appetite in Zn deficient bull calves. A loss of appetite results in lowered mineral ingestion, which further decreases feed utilization due to impaired nutrient metabolism. Relative bioavailability of zinc from grains and legume seeds averages about 60-70%. Supplemental sources like zinc sulphate and Zinc oxide are well utilized and their relative bioavailability is 100%.