Effect of lysine, tryptophan and(or) carbadox additions to low protein corn-soybean meal diets for young pigs.

Addition of L-lysine (Lys), L-tryptophan (Trp) and(or 55 ppm carbadox (C) to low protein corn-soybean meal diets was evaluated in two experiments using 444 crossbred pigs. In Exp. 1, initial and final weights of pigs were 17.7 and 33.3 kg, respectively, for the 28 d experiment. Pigs fed the 13% protein diet containing added Lys (.17%) or Lys + C had average daily gains (ADG) similar to those fed the 16% protein diet (positive control group) and greater (P less than .05) than those of pigs fed the 13% protein diet (negative controls). Pigs fed the 13% protein diets containing C had average daily feed intakes (ADFI) and ADG similar to those of pigs fed the 13% protein diet / Lys. Main effect comparisons among the 13% protein groups indicated that C increased (P less than .05) ADFI and ADG and that Lys increased (P less than .01) ADG and G:F ratio. In Exp. 2, the initial pig weight for the 28 d starter period averaged 7.4 kg. A 28 d grower period followed, in which the protein level was lowered 2% across treatments. The high and low dietary protein level sequences consisted of 18 and 15%, respectively, during the starter period followed by 16 and 13%, respectively, during the grower period. Lys and(or) Trp additions were also lowered from .18 and .05% to .15 and .04%, respectively. The overall 56 d performance indicated that pigs fed the low protein dietary sequence supplemented with either Lys or C had ADFI and ADG similar to those of the high protein dietary sequence positive control group and greater (P less than .05) than those of the low protein negative control group. The combination of Lys + C further increased (P less than .05) the ADG over that of the high protein sequence group. Overall main effect comparisons among the low protein dietary sequence groups indicated that either added Lys or C increased (P less than .01) ADFI and ADG, with added Lys also increasing G:F ratio. However, added Trp did not improve any performance characteristics. These results indicate that C had a Lys sparing effect in low protein corn-soybean meal diets fed to young pigs.