Effects of lighting pattern and dietary tryptophan supplementation on growth and mortality in broilers

The effect of lighting pattern and supplementation of the diet with Trp on growth and mortality of male broiler chickens was evaluated in three experiments using 2,392, 2,608, and 2,400 chickens, respectively. There were two lighting treatments, either a constant 23 h of continuous light/24-h period or an increasing photoperiod lighting system, i.e., 0 to 3 days, 23 h light (L):1 h dark (D); 4 to 14 days, 6L:18D; 15 to 21 days, 10L:14D; 22 to 28 days, 14L:10D; 29 to 35 days, 18L:6D; 36 to 42 days, 23L:1D. The design was a completely randomized 2 x 2 factorial, with four replicates per treatment. In the first two experiments, a starter diet with or without .2% supplemental L-Trp (feed grade) was fed from 0 to 3 wk of age and a finisher diet with or without .2% supplemental Trp was fed from 3 to 6 wk of age. In the third experiment, the level of supplemental Trp was .4% in the starter and finisher diet. Birds raised on the increasing light pattern consumed less feed during the first 3 wk, were lighter in weight at 3 wk, and had lower feed:gain ratios (P < .001) than their counterparts on constant light. By market age (6 wk) they had similar body weight but feed intake was significantly (P < .05) lower in all experiments, and feed:gain ratio was significantly lower in these birds in Experiment 3 (P < .05) than in their counterparts on constant light.(ABSTRACT TRUNCATED AT 250 WORDS)