Differential responses of Ross and Arian broilers to embryonic thermal manipulation and post-hatch heat stress

This study investigated the effects of heat stress and embryonic thermal manipulation (TM) on physiological, biochemical, and heat shock protein ۷۰ (HSP۷۰) gene expression in two broiler strains. A total of ۴۰۰ fertilized eggs were incubated under either normal (۳۷.۸ °C) or thermally manipulated (۳۹.۵ °C; embryonic day ۷ to ۱۶) conditions. Post-hatch chicks were reared under either normal (۲۵ °C) or heat stress (۳۲ °C; from day ۲۱ onward) conditions. The four experimental groups were defined as follows: Arian strain subjected to embryonic thermal manipulation but not to post-hatch heat stress (ATC); Arian strain without embryonic manipulation but subjected to post-hatch heat stress (ACH); Ross ۳۰۸ strain subjected to embryonic thermal manipulation but not to post-hatch heat stress (RTC); and Ross ۳۰۸ strain without embryonic manipulation but subjected to post-hatch heat stress (RCH). Blood parameters, lipid profiles, thyroid hormone (T۳) levels, and HSP۷۰ gene expression were analyzed at ۴۲ days of age. Significant differences were observed in red and white blood cell counts, hematocrit, and T۳ levels among treatments. RCH exhibited higher cholesterol (۱۵۷.۷۵±۲.۲۱) and LDL levels (۵۹.۶۷±۲.۸۸), whereas ATC showed higher T۳ levels (۸.۸۵±۰.۳۲) and spleen weight (۰.۱۷±۰.۰۲). HSP۷۰ gene expression was highest in RCH. The feed conversion ratio (FCR) was significantly lower in RCH (۱.۹۳±۰.۰۱). In conclusion, RCH demonstrated superior FCR under heat stress, while ATC modulate the thyroidal activity and immune responses following TM. Thermal manipulation during incubation reduced cholesterol, LDL, and HSP۷۰ levels, enhancing thermotolerance. These findings highlighted the potential of TM to mitigate the heat stress effects, emphasizing the importance of strain-specific strategies for optimizing the broiler performance in heat-stressed environments.

کلیدواژه ها:

Arian ، Heat stress ، Ross ، Thermal Manipulation