Vol. 9, Issue 9, Part A (2025)

Heat stress due to climatic change in cattle affects their overall health, production and performance. Cattle are homeotherms, initiate thermoregulatory mechanisms to heat stress. They employ antioxidant responses to counteract the oxidative stress due to environmental challenges. Antioxidant response is their endogenous ability to neutralise reactive oxygen species produced during heat stress. Enzymatic antioxidants like glutathione peroxidase (GPx) can quench the free radicals and prevent from cellular damage during heat stress. Measuring this bio-marker played a significant role in assessing the impact of high temperature and humidity on oxidative stress levels of cows. Rectal temperature is the ideal physiological bio-marker of quantifying heat stress responses in cattle. Surface temperatures measured at different anatomical locations by infrared thermometry is a precise, alternative non-invasive method for physiological assessment in heat-stressed cattle and can be an indicator of animal welfare. Hence the present study was conducted to assess the antioxidant and non-invasive physiological responses of crossbred calves to acute heat stress (Treatment) and compared it with thermo-neutral zone (Control) in a climate-controlled chamber. Venous blood samples with anti-coagulant were collected for spectrophotometric estimation of GPx activity in both the groups. Rectal temperature and surface temperatures of eye, forehead and flank were recorded on alternate days of experiment in both the groups. The study evidenced that the biochemical antioxidant responses were significantly increasing (p<0.001) from day one to ten of exposure to heat stress and remained constant in TNZ. The rectal temperature and surface temperatures of eye, forehead and flank were significantly increased (p<0.001) in the heat-stressed calves when compared to TNZ. The correlation studies shown that eye temperature was strongly correlated with rectal temperature under heat stress. It was evident from the findings that crossbred calves maintain thermal homeostasis by adopting antioxidant and physiological adaptations when they were exposed to environmental challenges under controlled climatic conditions. Furthermore, the study thrown light on the normal physiological and cellular functioning in crossbred calves under thermo-neutral zone.