Two hundred and forty male broilers, Avian Farms with average weight of 541 <FONT FACE=Symbol>±</FONT> 3.61 g from 22 to 42 days of age, kept under environment of high temperature were used to determining the lysine requirement. A completely randomized design, with five treatments (0.88, 0.94, 1.00, 1.06, and 1.12% of total lysine level), six replicates and eight broilers per replicate, was used. During the experimental period, the air temperature was maintained in 25.6 <FONT FACE=Symbol>±</FONT> 0.24ºC, the relative humidity in 68.4 <FONT FACE=Symbol>±</FONT> 6.30ºC, the black globe temperature in 25.7 <FONT FACE=Symbol>±</FONT> 0.25ºC and the black globe humidity index (BGHI) in 74 <FONT FACE=Symbol>±</FONT> 0.6. Feed and water were ad libitum fed to broilers. The dietary lysine levels affected the weight gain, that increased, and the feed:gain ratio, that increased and improved until the levels of 1.05 and 1.03%, respectively. Feed intake was not affected by the dietary lysine levels. For the carcass composition, it was observed that the treatments quadraticly affected the protein deposition rate, that increased up to 1.05% of lysine. The absolute weight of carcass, breast without bone, legs, thigh and of abdominal fat, as well as the relative weight of breast with bone and of abdominal fat, were affected by the treatments. It was concluded that male broilers from 22 to 42 days of age kept under 25.6ºC of environmental temperature require 1.05% of total lysine in the diet for maximum performance and protein deposition in the carcass.
broiler; growing phase; lysine; thermal environment
