Estimation of the tryptophan requirement of male broiler chickens

Three experiments were conducted to determine the response of the male broiler chick to tryptophan (TRP) supplementation. Chicks were fed from 7 to 18 or 7 to 20 days posthatch either a grain sorghum-soybean meal diet containing .16% TRP, supplemented with 0, .02, .04, .06, .09, or .11% L-TRP, or a corn-soybean meal positive control diet containing .25% TRP. Levels of TRP in all diets were confirmed by ion-exchange chromatography using an alkaline hydrolysis. The test diet contained 15.34% CP (N x 6.25) from intact ingredients and 20% CP (N x 6.25) when supplemented with other amino acids to 110% of National Research Council recommendations in 1984. No improvement in gain or feed efficiency was observed with chicks fed the grain sorghum-soybean meal diet at any level of TRP supplementation. Feed utilization but not weight gain of the chicks fed the TRP-supplemented test diets was significantly poorer than that of chicks fed the corn-soybean meal positive control diets. These results suggest that the TRP requirement of the young (0 to 21-day-old) broiler chicken is no greater than .16% of a diet containing 3,200 kcal ME/kg.