Productive features of broiler chickens in hot weather: Effects of strain and sex
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The objective of the present study was to evaluate the performance of broiler strains (Cobb 500, Ross 308, and Hubbard Flex) in hot weather. Environmental temperatures above thermal comfort trigger responses of the animals to maintain homeothermia, which negatively affects productive performance. A total of 2, 160 chicks of both sexes, were distributed in an experimental design that was completely randomized in a factorial arrangement of 3 × 2 (strains and sexes) with six replicates of 60 birds each. Feed intake (FI), live weight (LW), weight gain (WG), and feed conversion (FC) were analyzed at periods of 1-7, 1-21, 1-28, 1-42, and 1-49 days old. At 42 and 49 days old, the carcass weight (CW), carcass yield (CY), breast yield (BY), thigh yield (TY), and drumstick yield (DY) were analyzed. The strains differed in LW and WG in most periods, especially for Cobb broilers in the pre-start period (1-7 days) and Hubbard broilers in the last two periods (1-42 and 1-49 days). Except for the pre-initial stage, which there was no influence of the strains on FC, the Hubbard broilers showed the best FC, at 1-49 d, similarly to Cobb broilers. Regardless of strain, the males showed superior performance to that of females. At 42 d, the Cobb broilers showed a superior BY to that of the other strains, presenting better TY than did the Ross and Hubbard strains. At 49 d, the Cobb and Ross strains showed the best BY, with the Hubbard strain having the greatest DY. Males showed higher values in cut yields, except in the BY in which females showed better results.