Two trials were conduced to determinate the requirement of digestible lysine of broilers from 22 to 42 days, feeding diets maintaining or not the relationship of amino acids, kept under heat stress. A completely randomized experimental design was used in both trials. In trial 1, the broilers were allotted in five treatments (lysine levels in conventional diets) and six replicates with seven broilers in each. In trial 2, the broilers were allotted in four treatments (diets with different lysine levels, maintaining the relationship of amino acids) and six replicates with seven broilers in each. In both trials, the treatments improved in a linear way the weight gain and feed:gain ratio. However, although the feed:gain ratio had been improved by linear way, the LRP model better adjusted to the data, estimating in 0.92 and 1.022% the level of lysine where occurred a plateau, when it was used the conventional diet and it was considered the relationship of amino acids. There was no effect of treatments on feed intake and on relative and absolute weight of broiler's carcass when the relationship of amino acid was maintained or not. The lysine levels increased linearly the absolute weight and yield of breast of broilers, independent of maintained or not the profile of the amino acid. In the trial 1, the absolute and relative weights of thigh and drumstick were not influenced by treatments. The absolute and relative weights of abdominal fat were reduced in a linear way by lysine levels. In the trial 2, the absolute weight of thigh increased linearly with lysine levels of diet. There was no effect of the treatments on absolute and relative weights of drumstick and abdominal fat. It was concluded that male broilers, in the period from 22 to 42 days of age, kept under heat stress require at least 0.955 and 1.022% of digestible lysine in the conventional diet and in the diet maintaining the amino acid profile, respectively.
broilers; high temperature; ideal protein; lysine
