Effects of heat conditioning and dietary ascorbic acid supplementation on growth performance, carcass and meat quality characteristics in heat-stressed broilers

This study was conducted to investigate the effects of heat conditioning and dietary ascorbic acid supplementation on growth performance, carcass and meat quality characteristics in heat-stressed broilers. A total of 320 male broilers were randomly assigned to 4 treatment groups as positive control (PC), heat stress (HS), heat conditioning (HC) and ascorbic acid supplementation (AA). Broilers in PC group were housed in thermoneutral conditions (24 degrees C) and fed with the basal diet throughout experimental period. Heat stress group was exposed to 35 degrees C for 6 h daily between 4 and 6 weeks and fed with basal diet throughout experimental period. Heat conditioned group was exposed to 36 degrees C at 5 d of age for 24 h, fed on the basal diet throughout experimental period and was exposed to 35 degrees C for 6 h daily between 4 and 6 weeks. Ascorbic acid supplemented group was fed a diet supplemented with 500 mg/kg L-ascorbic acid and was exposed to 35 degrees C for 6 h daily between 4 and 6 weeks. Heat stress significantly decreased final body weight, weight gain (P<0.001), feed consumption, carcass yields (P<0.01), but increased feed conversion ratio and mortality rate (P<0.05). Heat stress decreased redness (P<0.001) and ultimate pH value (P<0.05), whereas increased lightness and cooking loss (P<0.001) of broiler breast meat. Heat conditioning and AA supplementation increased final body weight, weight gain, carcass yield and also improved quality characteristics of breast meat of broilers under heat stress: These results suggest that HC and dietary AA supplementation may alleviate the negative effects of heat stress on broiler performance and meat quality.