Some effects of dietary penicillin and zinc bacitracin on the performance of bacon pigs

Abstract

SUMMARY Three experiments were carried out to evaluate zinc bacitracin as compared with penicillin, as a feed supplement for bacon pigs. The first experiment compared pig performance on a control diet with performance on the control diet supplemented with penicillin, 5 g./ton, or with zinc bacitracin, 10 g./ton. Experiment 2 compared the control diet with penicillin at 10 g./ton and zinc bacitracin at 10 g./ton with pigs housed in a different piggery. Experiment 3 compared the control diet with penicillin at 10 g./ton and zinc bacitracin at two levels, 10 g./ton and 5 g./ton. In none of the experiments was there any significant response to penicillin in terms of rate of gain, feed conversion efficiency or carcass composition. In the first experiment there was a small but significant improvement in rate of gain up to 100 lb. live-weight and for the whole experimental period by the pigs receiving 10 g./ton of zinc bacitracin. There was no significant response in feed conversion efficiency or carcass measurements. In the other two experiments there was no response to zinc bacitracin. The implications of the results are discussed.