Turkish Journal of Veterinary & Animal Sciences




This study was designed to characterize changes in the acute phase proteins (APPs), hormones parallel to performance, and egg quality traits in laying hens exposed to heat stress (HS). A total of 120 sixteen-week-old Lohmann hens was allowed an adaptation period of 5 weeks in 3 different rooms at 21 °C. The hens were then exposed to one of three climatic thermal treatments over the next 6 weeks; thermoneutrality (TN, 21 °C), constant (C-HS, 28 °C), and cyclic HS (HS, 20 h/d at 28 ± 1 °C and 4 h/d at 33 ± 1 °C). Blood samples were weekly obtained, and serum levels of APPs [serum amyloid A (SAA), transferrin, and ovotransferrin], and hormones [leptin, triiodothyronine (T3), thyroxine (T4), and corticosterone] were measured. In addition, core body temperature (T$_{core}$), hen's body weight (BW), and egg quality parameters were recorded. Results indicated that SAA, transferrin, and ovotransferrin were not significantly (p > 0.05) different among the three thermal treatments in comparison with control; HS-hens had numerical increases of 2.46%, 3.46%, and 5.05% of the three APPs, respectively. Leptin levels were higher (p < 0.05), and T4 levels were lower (p < 0.05) in the HS than TN, meanwhile both C-HS and HS suppressed (p < 0.05) T3 levels in comparison with the TN. Furthermore, HS induced a significant variation (p < 0.05) in T$_{core}$ patterns, BW, eggs' number and weight, albumen height, and Haugh unit among the three thermal treatments. In conclusion, HS induced multiple changes in the APPs, hormones, performance, and egg quantity and quality parameters tested, and can potentially be used in future research as early biomarkers for stress in layers.

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