RESUMO
Early age thermal conditioning has been found to improve thermotolerance in birds. This study assessed the effect of perinatal thermal conditioning on serum parameters, corticosterone, free fatty acid, globulin and expression of corticotropin-releasing hormone (CRH) gene in five chicken strains; using fifty chicks per strain of Cobb 500 (C500), Ross 308 (R308), Shika Brown (SB), Normal Feathered Nigeria Indigenous (NF) and FUNAAB Alpha (FA). Twenty-five chicks per strain were conditioned at 40 ± 1 °C for 3 h on day 6. On day 10, both conditioned and unconditioned chicks were challenged acutely at 40 ± 1 °C for 15 min, without feed and water. Body weight and feed intake data were collected before and after the heat exposures. Blood samples were collected to determine serum electrolytes, metabolites and corticosterone levels. Brain tissue samples were collected from the 10-day-old conditioned and unconditioned chicks, from which RNA were extracted, synthesized into cDNA and subjected to qPCR. Serum parameters were significantly affected (p < 0.05) by strain, thermal conditioning and their interactions. Calcium and glucose concentrations were highest in NF while FA had highest in sodium. Calcium, glucose and phosphorus were higher in conditioned birds. NF had the highest free fatty acid while FA had the lowest. C500 had the highest globulin levels. Thermal conditioning significantly lowered corticosterone levels in conditioned birds. CRH was shown to be overexpressed in C500. From this research, it can be concluded that early age thermal conditioning affects body temperature regulation in chickens and enhances thermotolerance.
