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An experiment was conducted to determine the effects of dietary energy and protein on performance and carcass composition of broilers under heat stress during the growing period (3-6 weeks). A factorial arrangement of three levels of energy (3.0, 3.2 and 3.4 kcal/g), three levels of protein (18, 20 and 22%), an two rearing temperatures were used in this study. Groups of birds were kept under moderate temperature (24 1째C 24h) or hot cycling temperature (26-34째C 6 h, 34 1째C 12h, and 34-26째C g h). Body weight (BW), weight gain (WG), feed intake (FI), feed conversion (feed : gain) (FC), carcass weight (CW), carcass yield (YP), breast meat (BM), abdominal fat (AF), drumsticks (DS), and thighs (TH) percentages were determined at the end of the experiment. Hot cycling temperature significantly (p < 0.05) decreased BW, WG, FI, CW, and BM, increased FC, YP, DS and TH but did not affect AF. High energy significantly (p < 0.05) increased BW, WG, CW, YP, AF and TH, decreased FI and FC but did not affect BM or DS. This improvement was observed only under moderate temperature resulting in significant (p < 0.05) energy by temperature interaction. High protein significantly(p < 0.05) increased BW, WG, CW and BM, decreased AF but did not affect FI, FC, TP, DS or TH. There were no significant protein by temperature interaction for any of the parameters tested except CW. It is concluded, under the conditions imposed in this experiment, that increasing dietary energy did ot alleviate the depressing effect of heat stress while increasing dietary protein up to 22% improved the performance of broilers irrespective of rearing temperature. |
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