Value of Zinc Supplementation of Natural Rations for Fattening Beef Cattle

Four experiments were conducted with fattening beef cattle to study the effect of supplemental zinc to natural rations containing from 18 to 29 mg. of zinc/kg. Levels of zinc compared ranged from 75 to 346 mg./kg. In two of the four experiments, significant (P<.05) increases in daily gain were obtained from supplemental zinc. Increased levels of zinc resulted in significantly (P<.05) increased levels of serum zinc in the presence of either 0.25% or of .50% calcium in the ration. However, doubling the level of supplemental calcium resulted in significantly (P<.05) lower levels of serum zinc. Based on 112 day data, the level of zinc in the hair reflected the level of zinc in their rations. Furthermore, doubling the level of supplemental calcium in the ration resulted in significantly (P<.05) lower levels of hair zinc, based on the 112 day sample. However, the 201 day collection of hair failed to reveal any differences in zinc content, regardless of levels of dietary zinc or calcium, or both, indicating a possible compensatory reaction had been made by the cattle.