The effects of source of zinc on performance, nutrient utilization, and immune function in ruminants

Three experiments were conducted to evaluate the availability of different sources of Zn for ruminants. In the first experiment, lambs were supplemented with no supplemental Zn (control) or 20 mg of Zn/kg from Zn sulfate, Zn methionine, or Zn propionate to determine the effect of source of Zn on Zn absorption and retention in each of two collection periods. The control diet was removed from the analysis of the first collection period because it was contaminated with Zn. In both collection periods, absorption (P < 0.05) and retention (P < 0.05) of Zn was greater by lambs receiving Zn propionate than by lambs in the other treatments. In the second experiment, the effect of supplemental Zn on heifer performance during receiving and finishing phases was evaluated. Treatments were no supplemental Zn (control) or 75 mg of Zn/kg from Zn sulfate, Zn methionine, or Zn propionate. During the receiving phase, control heifers had a higher (P < 0.05) d-35 body weight (BW) and were more efficient (P < 0.05) than heifers in the other three treatments. Heifer morbidity did not differ (P > 0.10) among treatments for the 35-d receiving phase. Dry matter intake and daily gain did not differ (P > 0.05) among treatments for the 168-d finishing period; however, feed efficiency was poorer (P > 0.05) for control heifers than for the average of heifers in the other treatments. Carcass characteristics generally did not differ (P > 0.05) among treatments. The third experiment evaluated the effects of no supplemental Zn (control) or 75 mg of Zn/kg from Zn sulfate, Zn methionine, or Zn propionate on the humoral immune response of heifers injected with ovalbumin (OVA). Specific OVA antibody titers did not differ (P > 0.10) among the four treatments on any of the days measured. Results suggest that Zn propionate seems to be a more available source of Zn based on the data from the lamb trial; however, no major differences between the sources were observed for morbidity, performance, or the humoral immune response of heifers.