Dynamic responses of antioxidants in Tharparkar and Sahiwal during heat stress.

High environmental temperature induces oxidative stress, which affects animal performance as well as production. This study was carried out to assess the antioxidant responses in Tharparkar and Sahiwal under heat stress conditions. The experiment utilized Tharparkar and Sahiwal animals, and included a 7-day acclimatization period, a 21-day heat exposure period for the control (25 °C), moderate (35 °C) and severe (42 °C) heat stress groups, and 9 to 10 days for recovery between periods. Total antioxidant capacity (TAC), and the concentrations of serum glutathione peroxidase (GPx) and superoxide dismutase (SOD) were estimated in serum. The activities of TAC, GPx and SOD increased in both groups of animals when subjected to heat stress. There were no differences in serum GPx and TAC levels between the two groups but the serum level of SOD was significantly (p < 0.05) higher in Tharparkar than in Sahiwal animals. Therefore, Heat exposure elevated serum SOD, GPx, and TAC in both breeds, and the significantly higher SOD in Tharparkar suggests a stronger antioxidant defence and better thermo-adaptability than in Sahiwal.