A total of 3,760 Ross male broiler chicks were used in two trials, one in the pre-starter (1-11 days) phase and the other in the starter (12-22 days) phase. Birds were distributed in a completely randomized experimental design with a factorial arrangement of 5 digestible lysine levels × 2 environments (clean and dirty environment), with eight replicates per treatment. The following dietary digestible lysine levels used were: 1.06, 1.12, 1.18, 1.24 and 1.30% in the pre-starter phase, and 1.00, 1.06, 1.12, 1.18 and 1.24% in the starter phase. Minimal relation of digestible lysine:digestible methionine + cystine, threonine, tryptophan and arginine (72, 67, 19 and 108%, respectively) were maintained, as well as 2.088 and 2.002% of glycine+serine in the pre-starter and starter diets, respectively. Weight gain, feed intake and feed conversion were evaluated. In all phases, dietary digestible lysine levels significantly influenced broiler performance, and broilers reared in the clean environment presented better performance than those reared in the dirty environment. The recommended digestible lysine levels during the pre-starter and starter phases are 1.30 and 1.24% when broilers are reared in the clean enviroment and 1.26 and 1.165% in the dirty enviroment, respectively.
digestible amino acids; nutritional requirements; performance
