EFFECTS OF EXCESS DIETARY LEUCINE AND LEUCINE CATABOLITES ON GROWTH AND IMMUNE-RESPONSES IN WEANLING PIGS

Two experiments with weanling pigs were conducted to study the effects on growth and immune responses of excess dietary L-leucine (LEU) and dietary supplementation with the LEU catabolites, alpha-ketoisocaproic acid (KIC) and beta-hydroxymethyl butyrate (HMB). In Exp. 1, 80 pigs were randomly allocated according to initial BW and ancestry to five r eplications of four dietary treatments (four pigs/pen). The control di et contained wheat, oat greats, menhaden fish meal, and dried whey and provided 1.12% LEU. Treatment diets were the control plus 1.12% LEU, 1.12% KIC, or .4% HMB. The experiment lasted 6 wk. In Exp. 2, 36 pigs were randomly allocated to nine replications of four dietary treatment s in a 2 x 2 factorial arrangement. Treatments consisted of two concen trations of dietary LEU and a daily i.m. injection of dexamethasone (D EX) or saline. Pigs were fed a control corn-soybean meal and dried whe y diet (1.56% LEU) or the control diet plus 1.56% of crystalline LEU. Pigs were individually penned and the experiment lasted 4 wk. Growth p erformance, plasma free amino acids, plasma urea nitrogen, and humoral and cellular immune responses were measured. Results indicated that L EU concentrations in practical diets and supplementation with KIC and HMB (Exp. 1) did not detrimentally affect growth and immune response. The high LEU concentration and DEX injection used in Exp. 2, however, were detrimental to both growth and immune response.