Vol. 8, Special Issue 12, Part C (2024)

Heat stress generally affects the overall production, productivity and well-being of livestock. Cattle are homeotherms, initiate thermo-regulatory mechanisms to maintain homeostasis. Rectal temperature is the ideal physiological biomarker of quantifying HS response in cattle. They also employ biochemical adaptations to counteract the oxidative stress due to temperature-humidity challenges. Antioxidant defense responses of cattle is their mechanism to neutralise the reactive oxygen species produced during heat stress. Enzymatic antioxidants such as glutathione peroxidase (GPx) scavenge the free radicals and prevent from cellular damage due to oxidative stress during heat stress. The present study was conducted to explore the biochemical adaptations exhibited by crossbred (Holstein Friesian × Sahiwal) calves to acute heat stress (Treatment) and compared it with thermo-neutral zone (Control) in an environmentally-controlled chamber. Rectal temperature was recorded on days zero, one, five and 10 in both the groups to correlate with the biochemical responses. Venous blood samples with anti-coagulant were collected on same days for spectrophotometric estimation of GPx activity and total antioxidant capacity by ferric reducing ability of plasma (FRAP) assay in both the groups. The study shown that the rectal temperature was significantly increased (p<0.001) in the heat-stressed calves. The biochemical antioxidant responses were significantly increasing (p<0.001) from day one to ten of heat stress and remained constant in thermo-neutral zone. Further, there was a strong positive correlation of rectal temperature with FRAP and GPx values found under heat stress. It was evident from the findings that crossbred calves were trying to maintain thermal homeostasis by adapting physiological and biochemical adaptations when they were exposed to controlled environmental challenges and elucidated the antioxidant defense mechanisms adapted by them to counteract the oxidative stress. The findings also thrown light on the normal cellular functioning of crossbred calves under thermo-neutral zone.