The response of growth performance and meat quality of broiler chickens to an experimental model of cyclical heat stress

Due to rapid growth rates and body weight gain, broiler chickens are sensitive to high temperature that causes heat stress. This study was undertaken to investigate the effects of cyclical high temperature on growth performance and meat quality of broiler chickens from 21 to 35 d of age. A total of 80 day old male Ross 308 broiler chicks were used for this study. All chicks were kept in metabolism cages at standard brooding temperatures until 21 days of age and then exposed to either a standard temperature (22 ± 1°C; RH 60%); or cyclical high temperature (32 ± 1°C; 8 h; 80-90% RH and 16 h at 22 ± 1°C; RH 60%);) with 8 replicate cages with 5 birds in each. Birds were offered common wheat, soybean meal-based diet containing endogenous selenium only. Average individual body weight (BW), average daily feed intake (ADFI), average daily gain (ADG), feed conversion ratio (FCR) from 21-35 d, and pectoralis muscle shear force, colour, temperature, pH, and drip loss rate at 35 d were evaluated. Results of this study show that ADFI, ADG and BW of birds from 28-35 d of age were significantly lower in the cyclical high temperature group. The breast meat of the birds from the cyclical high temperature group had significantly higher shear force, lightness (L*) and yellowness (b*) values as well as a lower redness (a*) value compared to birds from the standard temperature group. The results of this study show that cyclical high temperature significantly reduced growth performance, increased meat shear force value and reduced meat colour, and eventually reduced meat quality. These findings provide targets to improve broiler productivity in systems affected by cyclical heat waves.