Acquisition of thermotolerance in slow growing poultry: Elucidating through sequential mechanism of thermal conditioning during embryonic and early post-hatch period

Abstract

Abstract This study aimed to elucidate the impact of embryonic thermal conditioning (ETC) in combination with early post-hatch heat conditioning (PHHC) on acquired thermotolerance in slow growing CARI-Debendra birds till 12 weeks. Embryonic conditioning was done only from E11-16 at 39.5°C with RH 60–70% for 5hrs/ day while conventional incubational conditions followed in control. After hatching, the chicks were chosen in a random manner group-wise and further distributed in to two sub groups each (No manipulation, early post-hatch heat conditioning). Early post-hatch heat conditioning was carried out for first five weeks for chicks with brooding temperature of 37 ± 1°C than control. Significant difference was observed in hatch weight and hatching time between ETC and control without any adverse effect on fertility and hatchability. Rectal temperature and surface temperature in ETC group were + 1.04 and + 4.76% higher than the control at hatch which diminishes with age. ETC had improved body weight from 1st wk till 12th wks while heat conditioning group displayed a 1% increase in body weight at six weeks. Stress biomarkers such as concentration of T4, potassium and activity of creatinine kinase enzyme was more in ETC group than control while H/L ratio and concentration of T3 was less in ETC group. Expression dynamics of HSP70 gene was significant only in liver and intestine tissues of ETC group respectively, while GRP78 gene showed tissue-specific upregulation in the intestine of 12-week-old chickens. Embryonic thermal manipulation and early post-hatch heat conditioning positively influenced thermotolerance ability and productivity of slow growing birds.