Two trials were conducted to evaluate the requirements of increasing dietary digestible lysine levels, maintaining or not the amino acids relation, for broilers from 1 to 21 days old, on thermoneutral environment. A complete randomized experimental design was used in both trials. In trial 1, broilers were allotted to five treatments (0.92, 0.98, 1.04, 1.10, and 1.16% digestible lysine levels, conventional diet), with eight replicates of ten birds. In trial 2, chicks were allotted to four treatments (1.04, 1.10, 1.16, and 1.22% of digestible lysine, in diets maintaining amino acid relation) with eight replicates of ten birds. In trial 1, effects of dietary lysine levels on body weight gain and feed intake, both increasing quadraticly up to 1.13 and 1.11% digestible lysine, respectively, were observed. There was significant treatment effect on feed:gain ratio, that decreased quadraticly up to 1.14% digestible lysine. Absolute carcass weight increased quadractily while relative carcass values and absolute weight of gizzard increased linearly with treatments. Relative weights of heart and intestines decreased linearly with the treatments. In trial 2, body weight gain also increased linearly with treatments, the LRP model better adjusted to data, where the 1.17% digestible lysine level was estimated. No effects of treatments on feed intake and feed:gain ratio were detected. Absolute carcass weight was linearly affected by the increasing dietary lysine levels. There was no effect of dietary lysine levels on absolute and relative weights of all evaluated organs. It was concluded that Avian Farms male broilers, in the period from 1 to 21 days, require at least 1.14 and 1.17% digestible lysine, in a conventional diet or of a diet maintaining the amino acid relation, respectively, on a thermoneutral environment.
broilers; digestible lysine; ideal protein; thermoneutrality
