Thermoregulatory Responses of Karan Fries Cattle during Thermal Exposures

To quantify the effect of thermal exposure on heat production, heat storage, heat exchange and physiological responses, six each of growing and adult Karan Fries (crossbred) cattle were selected. These animals were exposed for four hours continuously at 20, 30 and 40°C with 40–45% relative humidity in a climatic chamber and also in natural ambient conditions during winter and summer seasons for three days consecutively. Physiological cardinal reactions (RR, RT and ST) and metabolic heat production of growing and adult Karan Fries cattle increased significantly (p<0.05) on exposure at 30, 40°C in climatic chamber and during summer season. Sensible heat loss through radiation, convection, conduction occurred at 20°C and during winter whereas heat gain was observed at 30 and 40°C in climatic chamber and during summer season. Partitioning of heat loss in growing and adult Karan Fries cattle indicated higher proportion of heat loss through sweating than panting. Heat storage was significantly (p<0.05) higher at 40°C and during summer compared to other temperature exposure conditions. The results of the present study indicated that both groups of Karan Fries cattle gained more heat through radiation, conduction and convection at 40°C compared to heat loss through sweating and panting, therefore, these animals may requires extra protection for maintenance of homeothermy.