This study wasperformed to evaluate the effects of reduction of dietary crude protein levelwith supplementation of industrial amino acids on the performance and carcassyield of broilers between 22 to 42 days of age, under heat stress. It was used280 Cobb broilers with initial weight of 856 ± 7.41 g, distributed ina complete randomized experimental design, with five crude protein levels (21.6;20.6; 19.6; 18.6 and 17.6%), eight repetitions and seven broilers per experimentalunit. The temperature inside the rooms was kept at 32.2 ± 0.6ºC, therelative humidity at 66 ± 3.2% and black globe temperature at 33.0 ±0.7°C. The black globe-humidity index calculated for the period was 83 ±0.9. There was no effect of crude protein levels on weight gain, feed intakeand feed conversion of the birds. The reduction of dietary crude protein levelsinfluenced the absolute weight of carcass and breast, and the level of 19.6%proportioned higher carcass and breast weights of the broilers compared to thelevel of 21.6% of crude protein. However, there was no effect of the reductionof levels of crude protein on absolute values of thigh and drumstick and alsoon breast, thigh and drumstick yields. The dietary crude protein level, formulatedby using the ideal protein concept, can be reduced from 21.6 to 17.6% not negativelyaffecting the performance, absolute weight and noble cut yield of broilers underheat stress.
