Effects of early and chronic exposure to high temperatures on growth performance, carcass parameters and fatty acids of subcutaneous lipid of broilers
This study was conducted to assess the effects of early and chronic exposure of broilers at a scorching temperature on growth performance, carcass parameters, fatty acid deposition and composition of subcutaneous lipids (SCL). Three hundred male chicks (Hubbard origin) of a day are reared for 50 days. They are divided into three groups, each of cent chicks. The chronic thermal environments are applied from the 8th growing day: a neutral temperature (NT: 25 ± 2°C) for the first one, a moderate summer temperature (MT: 32 ± 2°C) for the second and hot temperature (HT: 37 ± 2°C) for the third. The results were summarized as follows: (1) from the 40th day, a decrease of 37 g/d of feed intake (FI) related to HT was observed; (2) a higher body weight (BW) of NT chickens was recorded from the 40th day; (3) regarding the early breeding, a higher daily weight gain (DWG) was recorded in HT chickens at the end of rearing; (4) compared to other temperature, the feed conversion ratio (FCR) of HT chickens was significantly better from 40th day; (5) at the end of breeding, the yields EC/BW: eviscerated carcass weight (EC) on body weight (BW) were comparable as recorded in NT and HT chickens; (6) at the end of breeding, a decreased weight of pectoral muscle (PM) associated with the HT was observed: -17 and - 20% compared with TM and TN, respectively; (7) a higher deposit of SCL up to 105g/Chicken and SCL/EC (+7.3% compared with NT) occur in the HT chickens mainly at the end of rearing; (8) conversely, the abdominal fat weight (AF) was higher in NT chickens from the 32th day; (9) compared with NT chickens, an increase in the proportion of saturated fatty acids (SFA) and polyunsaturated (PUFA) of SCL was obtained in HT chickens of 50 days. No temperature effect on the monounsaturated fatty acids proportion (MUFA) of LSC has been highlighted. Finally, the HT resulted in a significant decrease of the UFA/SFA ratio reflecting a degree of SCL saturation greater in HT chicken carcass; (10) these results have shown that chickens can tolerate early and chronic higher temperatures.
Keys words: Temperature, broilers, growth, subcutaneous lipids, fatty acids.