Zinc concentration in tissues and performance of weanling pigs fed pharmacological levels of zinc from ZnO, Zn-methionine, Zn-lysine, or ZnSO4.

Four trials were conducted to examine concentration of zinc in tissues and performance of pigs fed high levels of Zn from ZnO, Zn-methionine, Zn-lysine, or ZnSO4. In Trials 1 (n = 80, 28 d of age, 7.5 kg BW), 2 (n = 80, 26 d of age, 7.1 kg BW), and 3 (n = 70, 23 d of age, 5.3 kg BW), pigs were assigned either to a control diet containing 105 mg/kg of Zn and 15 mg/kg of Cu or to supplemental dietary treatments of 3,000, 2,000, or 1,000 mg of Zn/kg of diet. In all three trials, dietary sources were ZnO, Zn-methionine, Zn-lysine, or ZnSO4. The trials lasted 2 wk. In Trial 1, performance of pigs generally was not improved by feeding 3,000 mg of Zn/kg from any of the Zn sources. Serum, liver, and rib Zn concentrations (P < .01) and liver Zn concentrations (P < .05) were greater for pigs fed the high Zn diets. In Trial 2, feeding high Zn did not affect overall performance. Pigs fed the high Zn diets had greater (P < .01) serum, liver, kidney, and rib Zn concentrations. In Trial 3, there were no differences (P > .10) in ADG or ADFI, but serum and liver Zn concentrations were greater (P < .01 and .05, respectively) for pigs fed high Zn diets. Within Zn sources, serum and liver concentrations of Zn were greater (P < .05) for pigs fed ZnSO4 rather than ZnO in Trials 1 and 2. In Trial 4 (n = 72, 7.1 kg), 25-d-old pigs fed diets containing 3,000 mg/kg of Zn from feed-grade ZnSO4, reagent-grade ZnSO4, or feed-grade ZnO in a 4-wk growth trial had similar ADG and ADFI, but the gain:feed ratio was lower (P < .05) for pigs fed the reagent-grade ZnSO4. Serum, liver, and kidney Zn concentrations were lower (P < .05) for pigs fed the ZnO diet after wk 2 than for pigs fed the ZnSO4 diets, but no differences (P > .10) were observed at the end of wk 4. In summary, performance was not enhanced by feeding pharmacological levels of zinc after weaning, although serum and tissue Zn concentrations were increased. When compared with the bioavailability of Zn in ZnSO4, the bioavailability of Zn was lowest for ZnO and intermediate for Zn-lysine and Zn-methionine.