This study was aimed to evaluate the effects of the dietary digestible lysine levels and environmental temperature on performance and carcass characteristics of broiler chickens from 22 to 42 days-old. Six hundred seventy two males Ross® broiler chickens with an average weight of 726 g were allotted to a completely randomized design, in a 4 × 4 factorial arrangement with six replicates and seven birds per experimental unit. The chickens were fed with different digestible lysine levels in the diet (0.934, 1.009, 1.084, and 1.159%) and kept under different environmental temperatures (18.5, 21.1, 24.5, and 27.0°C). There were no interactions between environmental temperature and lysine levels in the diet for the studied variables. Feed intake and the weight gain (WG) were not influenced by lysine levels in the diet. Feed intake linearly reduced with the environmental temperature and the WG increased up to the estimated temperature of 21.5°C. The feed:gain ratio improved up to the estimated digestible lysine level in the diet of 1.085%. The weights of carcass (CW), boned breast (BBW), thigh (TW) and drumstick (DW) increased up to the estimated temperatures of 21.9, 21.7, 22.7, and 23.7°C, respectively. The yields of carcass (CY), thigh (TY) and drumstick (DY) increased, whereas the deboned breast weight (DBW), the boned breast yield (BBY) and deboned breast yield (DBY) linearly decreased with the environmental temperature. The TW and TY increased, whereas the DY linearly decreased with the lysine levels in the diet. The lysine levels did not influence the CW, BBW, DW, CY, BBY and DBY. The environmental temperature in the range from 18.5 to 27.0°C did not influence the lysine requirements of the birds. The condition that provided better feed:gain ratio during the experimental period was obtained with the digestible lysine level in the diet of 1.085% and the estimated environmental temperature of 23.3°C.
amino acids; nutritional requirements; performance; poultry; thermal environment
