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Virginiamycin, Protein and Lysine Responses of Young Swine¹

Purdue University, Agricultural Experiment Station, West Lafayette, Indiana 47907

Abstract

Two experiments with 216 weanling pigs averaging 12 kg were conducted in confinement to evaluate (1) addition of 0 vs 44 ppm virginiamycin to starter diets for 42 days; (2) protein-virginiamycin interactions in protein adequate starter diets, (18% crude protein [CP], .88% lysine), protein-deficient diets (15% CP, .66% lysine) and L-lysine-supplemented starter diets (15% CP, .88% lysine); (3) L-lysine supplementation of protein-deficient starter and grower diets, and (4) the residual effect of virginiamycin fed in the starter diet for 42 days and then withdrawn from the grower diet for 35 days. Addition of virginiamycin to 18%-protein starter diets for 42 days improved gains (P<.01) in both experiments. In the L-lysine-supplemented diet, virginiamycin improved gains (P<.01) only in Exp. 2. Its withdrawal from the diet during the 35-day grower phase resulted in pig performance similar to that of pigs that had not received it. The virginiamycin main effect was significant for feed:gain ratios for 42 and 77 days in Exp. 1. In the starter phase, the main effects for protein showed faster and more efficient gains with the 18%-protein diet than with the 15%-protein diet; however, these responses were significant only in Exp. 1. L-lysine supplementation improved gains and feed efficiency of pigs on the 15%-protein diet in both trials, but the improvement was significant only in Exp. 1. Gains and feed efficiency were improved (P<.05) with the 18%-protein diet then with the L-lysine diet in Exp. 1. In the grower phase,the 15%-protein diet produced faster and more efficient gains (P<.05) than the 12%-protein diet in both trials. L-lysine supplementation improved the feed to gain ratio (P<.05) for the 12%-protein diet in both trials, but improved gains only in Exp. 1. The 15%-protein diet improved gains and feed efficiency over the 12%-protein diet plus lysine in both trials, but the difference was significant only in Exp. 1. Overall, the 18-15% protein and the 15-12% protein plus lysine sequences produced faster and more efficient gains (P<.05) than the 15-12% protein sequence in both trials. The 18-15% protein diets were more efficient (P<.05) than the 15-12% protein diets plus lysine only in Exp. 1.

¹ Journal Paper No. 7388, Purdue University Agricultural Experiment Station, Department of Animal Sciences. The research reported in this paper was supported in part by a grant from Smith Kline Animal Health Products, Philadelphia, PA, as well as supplies of virginiamycin and assays of the diets.