Resiliency of fast-growing and slow-growing genotypes of broiler chickens submitted to different environmental temperatures: growth performance and meat quality

Growth performance and meat quality were assessed in 238 chicks of both sexes belonging to a commercial crossbreed (Ross 308), and 2 Italian local breeds (Bionda Piemontese-BP and Robusta Maculata-RM). The chickens were kept in 2 rooms at standard environmental conditions or under heat stress (+4.7degree celsius on average) until slaughtering (42 d of age for Ross 308 and 99 d for RM and BP chickens). The Ross chickens showed the highest final live weight, feed intake, and daily weight gain, and the best feed conversion ratio compared to the local breeds (P < 0.001), with RM performing better than BP chickens. Thus, Ross chickens had the heaviest carcasses, the highest slaughter, and breast yields followed by RM and BP chickens (P < 0.001). At the pectoralis major (p. major) muscle, Ross chickens showed the highest pH, lightness, and yellowness, besides the highest cooking losses, whereas BP showed the highest redness (P < 0.001). Ross meat had higher water and ether extract contents, and lower crude protein content compared to BP and RM (P < 0.001), whereas no differences among genotypes were measured for the fatty acid profile. At the sensory analysis, Ross breasts had a higher juiciness compared to BP ones, besides a lower score for "brothy and chickeny/meaty" and a higher one for "wet feathers" compared to local breeds (0.05 < P < 0.001). The increase of the room temperature decreased growth performance and cold carcass weight (P < 0.001) compared to standard conditions, whereas the rate of a-linolenic acid in the meat increased (P < 0.01). The effect of a high environmental temperature on growth performance and slaughter and meat quality traits was more pronounced in Ross compared to BP and RM chickens (0.05 < P <0.001; significant interaction genotype x temperature). In conclusions, local chicken breeds showed lower performance and slaughter yield compared to the commercial genotype, but more favorable meat quality traits and higher resilience to the environmental heat-stress.