关键词: 肉鸡, 有效温度, 代谢能, 生产性能, 胴体组成

Abstract: In a 4×3 factorial design trial, 216 21-day-old Arbor Acre (AA) broilers were randomly allocated into 12 groups, each with 3 replicates of 6 birds, reared in 4 chambers which effective temperature (ET) was controlled at 15.0, 21.2, 35.3 and 37.6℃, respectively, and fed on one of the trial diets containing 11.71, 12.55 and 13.39 MJ/kg ME, respectively, for three weeks. Body weight and feed consumption were measured at d 21 and d 42. After feeding trial, two birds from each replicate were slaughtered for carcass and meat measurement. The results showed that: (1) Under high temperature (35.3℃ and 37.6℃), average daily feed intake (ADFI) and average daily gain (ADG) significantly decreased (P<0.05), and feed conversion rate (FCR) markedly rose (P<0.05). Trial dietary ME level and the interaction between ET and ME had no remarkable effect on performance. (2) High temperature (35.3℃ or 37.6℃) increased significantly the ratio of carcass yield to live weight, percentage of halfeviscerated yield, percentage of eviscerated yield and the ratio of meat yield in left thigh and drumstick to uneviscerated carcass yield (P<0.05), but decreased significantly carcass yield, meat yield in right breast, meat yield in left thigh and drumstick, the ratio of meat yield in right breast to uneviscerated carcass yield, subcutaneous fat thickness and fat width between muscles(P<0.05). Under low temperature the ratio of carcass yield to live weight increased and subcutaneous fat thickness decreased significantly (P<0.05). Carcass yield increased, and the ratio of meat yield in right breast to uneviscerated carcass yield and subcutaneous fat thickness decreased significantly (P<005), as the dietary ME level rose. (3) High temperature (37.6℃) decreased the protein of breast meat and thigh meat significantly (P<0.05); Both high and low temperature significantly increased the fat deposition of breast and thigh meat (P<0.05); High temperature (35.3℃ and 37.6℃) increased the moisture of breast meat significantly (P<0.05); Low temperature decreased the meat ash significantly (P<0.05). The protein of thigh meat in the broilers reared under high dietary ME was significantly lower than that under proper dietary ME (P<0.05). It was concluded that ET had more significant effect on performance and carcass composition in broiler than dietary ME level, and that there were lower performance, carcass composition and crude protein content in meat in broiler reared under high temperature.

Key words: broiler, effective temperature, metabolizable energy, performance, carcass composition