This study wasaimed to evaluate the effects of the dietary digestible lysine levels and environmentaltemperature on performance and carcass characteristics of broiler chickens from22 to 42 days-old. Six hundred seventy two males Ross® broilerchickens with an average weight of 726 g were allotted to a completely randomizeddesign, in a 4 × 4 factorial arrangement with six replicates and sevenbirds per experimental unit. The chickens were fed with different digestiblelysine levels in the diet (0.934, 1.009, 1.084, and 1.159%) and kept under differentenvironmental temperatures (18.5, 21.1, 24.5, and 27.0°C). There were nointeractions between environmental temperature and lysine levels in the dietfor the studied variables. Feed intake and the weight gain (WG) were not influencedby lysine levels in the diet. Feed intake linearly reduced with the environmentaltemperature 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 inthe 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) anddrumstick (DY) increased, whereas the deboned breast weight (DBW), the bonedbreast yield (BBY) and deboned breast yield (DBY) linearly decreased with theenvironmental temperature. The TW and TY increased, whereas the DY linearlydecreased with the lysine levels in the diet. The lysine levels did not influencethe CW, BBW, DW, CY, BBY and DBY. The environmental temperature in the rangefrom 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 periodwas obtained with the digestible lysine level in the diet of 1.085% and theestimated environmental temperature of 23.3°C.
