Delay in puberty is dependent on heat shock protein B1 expression in native cross layers of Punjab under heat stress

Small heat shock protein B1 (HspB1) has been reported to play an essential role in thermotolerance. This study aimed to determine a correlation (if any) between HspB1 expression and age at first egg lay (puberty) in a native cross-layer poultry of Punjab under heat stress. Forty native cross-layer birds were reared in two different seasons, viz. summer (THI was more than 27), classified as the heat-stressed group (n = 20) and winter season (THI was less than 21), classified as the control group (n = 20). Blood was collected from both the groups of birds in their 15^th week of age and at puberty. Serum catalase and superoxide dismutase activities, reduced glutathione and corticosterone concentration and lipid peroxidation were measured to assess the oxidative stress in both the groups of birds. The serum antioxidants significantly decreased whilst corticosterone levels and lipid peroxidation significantly elevated in birds in response to summer heat stress. Moreover, in summer season, the activities of the antioxidant enzymes further decreased and lipid peroxidation further increased significantly in birds from their pre-pubertal stage to puberty, which was not observed during the winter season. A clone of chicken HspB1 in BL21 (DE3) cells was revived, and recombinant HspB1 was purified using Ni-NTA agarose column. Serum HspB1 concentration was estimated in different groups of birds by indirect ELISA that has been standardized using the recombinant chicken HspB1. Compared to the control, birds under heat stress had significantly higher serum HspB1 levels. The delay in puberty of all the heat-stressed birds was significantly associated with the increase in their serum HspB1 levels. Taken together, the expression of HspB1 was found to be associated with age at puberty in the native cross poultry layers of Punjab.