Italian Journal of Animal Science (Jan 2021)
Hepatic expression responses of DNA methyltransferases, heat shock proteins, antioxidant enzymes, and NADPH 4 to early life thermal conditioning in broiler chickens
Abstract
Early-life thermal conditioning (TC) in broiler chickens has long-lasting impacts on later life. Therefore, this study aimed to clarify the molecular mechanism by which TC impacts the hepatic expression heat shock proteins (hsps), antioxidant enzymes, NADPH oxidase 4 (NOX4), glucocorticoid receptor (GR), and DNA methyltransferases genes in broiler chicks at five weeks of age. Two hundred forty one-day-old male broiler chicks of Cobb 500 were allocated into four equal experimental groups. The first group was under the optimal brooding conditions (control), whereas the 2nd, 3rd, and 4th groups were exposed to TC at 39 ± 1 °C for six hours on the third-, fifth- or seventh-day post-hatch, respectively. At 35 days of age, all chicks of four experimental groups were subjected to heat challenge by exposure to 36 ± 1 °C for six hours. Results showed that broilers exposed to TC on the fifth-day post-hatch when exposed to acute heat stress at five weeks of age had the lowest plasma CORT level, the lowest expression (p < .05) for NOX4, GR, SOD, SOD2, and CAT among all groups. The same trend was observed for hsp70, hsp90A, hsp90B, hsp60, and hspA9. In conclusion, early thermal conditioning on the fifth-day post-hatch may improve thermotolerance by decreasing NOX4 and GR expressions, leading to reduced heat shock proteins and antioxidant enzyme gene expression subsequently reduced oxidative stress.Highlights Thermal conditioning is a promising approach to mitigate heat stress in broiler chicks. The optimal age to perform thermal conditioning is a controversial issue. Heat shock proteins gene expression and plasma corticosterone are good indicators for thermotolerance acquisition. Thermal conditioning on the fifth-day post-hatch reduced oxidative stress at five weeks of age.
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