With the objective to determine the tryptophan nutritional requirements for male and female broilers, during the initial phase, 800 male and female chicks, from 1 to 21 days of age, with average initial weight of 44.7 and 44.6 g, respectively, were used. The birds received a deficient tryptophan basal diet (.180%). A completely randomized blocks experimental design, in a 5 x 2 factorial arrangement (treatment x sex), with four replicates per sex and 20 chicks per experimental unit, was used. The treatments consisted on a basal diet supplemented with five tryptophan levels (0, .015, .030, .045, and .060%). Chick's performance was evaluated, and the tryptophan requirement values were estimated by means of the polynomial regression models and LRP. The tryptophan true digestibility coefficient of the basal diet was 90.33%. The supplementations with L-tryptophan influenced the males weight gain, however, there was no effect on the feed: gain, suggesting a minimum recommendation of .212 and .195% for total tryptophan and digestible, respectively. However, for the females, the supplementations with L- tryptophan influenced the weight gain and the feed: gain, suggesting a minimum recommendation of .208 and .191% for total and digestible tryptophan, respectively.
amino acid; broiler; requirement; tryptophan
