The experiment was conducted with the objective evaluating the different digestible threonine: digestible lysine ratio and supplementation or not of glycine on the performance of broilers in the period from eight to 21 days of age. Five hundred and sixty male broiler chicks of the Cobb strain were used, distributed in a completely randomized design, in a factorial arrangement of 3 x 2 + 1, with three digestible threonine:lysine ratio (55, 65 and 75%), supplemented or not with glycine plus an additional treatment, containing animal protein, with digestible threonine:lysine ratio of 65%. Eight replicates were used per treatment and 10 birds were used per experimental unit. The feed intake, the weight gain and the feed conversion were not influenced by the levels of threonine. The supplementation of glycine reduced the feed intake, increased the weight gain and improved the feed conversion of the birds. There was no interaction between the levels of threonine and the supplementation of glycine on the broilers performance. The supplementation of glycine was essential to improve the broiler chicks performance. The digestible threonine: lysine ratio of 55% (0.631% of digestible threonine), supplemented with glycine is sufficient to meet the requirements of broiler chicks from 8 to 21 days of age.
essential amino acids; feed conversion; feed intake; weight gain