Four hundred and eighty Ross broiler male, with initial weight of 43 ± 0.2 g, from 1 to 21 days of age, were allotted to an experimental design in 2 x 4 factorial arrangement, two environments (high temperature and thermal comfort) and four levels of total lysine (1.1, 1.2, 1.3 and 1.4%) with six replicates and ten birds/experimental unity. Feed intake (FI) and weight gain (WG) were higher in the thermoneutral environment, while the feed: gain ratio (F/G) and the efficiency of utilization of lysine were better at the high environmental temperature. At the thermal comfort environment, the WG and lysine intake increased with the dietary lysine levels in the diet and the efficiency of lysine utilization for WG linearly improved. At the high temperature environment, the lysine levels influenced the WG and lysine intake, which linearly increased, and also improved, in a linear response, the efficiency of lysine utilization for WG. The feed: gain ratio improved in a quadratic way up to the level of 1.29% of lysine. Despite of the linear response, the LRP model was the one that better fitted the WG data, estimating the lysine level in 1.24%, the plateau point. The high temperature environment negatively influenced WG and FI, even so improved the FC. Broilers from 1 to 21 days of age need 1.4 and 1.29% of total lysine, in thermal comfort and high temperature environments, respectively.
broiler chick; heat stress; performance; thermal comfort environment
