Indian Journal of Animal Nutrition

Ten each of periparturient Karan Fries and Sahiwal cows were selected separately during summer and winter season. These animals were equally divided (five each) into two groups i.e. high and low yielding on the basis of their earlier lactation milk yield. The cows were maintained on standard conditions of feeding and management followed at the Institute farm. The physiological responses (RR, PR, T_re and T_skin) and climatic variables (T_db, T_wb, T_max, T_min, RH and THI) were recorded-45, -30, -15, and 15, 30, and 45 with respect to day of parturition (day 0) and the heat storage of these animals were calculated. The physiological responses and heat storage were significantly (P<0.05) higher during summer compared to winter season. The magnitude of increase in physiological responses were higher (P<0.05) in high and low yielding Karan Fries cows compared to both the groups of Sahiwal cows during both the seasons. The mean values of heat storage increased by 6.20 and 1.80% in high and low yielding Sahiwal cows during summer season, whereas, in high and low yielding Karan Fries cows the increase was 6.70 and 5.40%, respectively, on the day of calving from the pre-calving values (45^th day). During winter season the values of heat storage, increased by 2.60 and 4.40% in high and low yielding Sahiwal cows, whereas, the respective increase in high and low yielding Karan Fries cows was 6.10 and 6.04%, respectively, on the day of calving from the pre calving values (45^th day). The overall mean values showed significantly (P<0.05) higher values of heat storage during summer, in high yielding and in KF cows compared to winter season, low yielder and Sahiwal cows respectively. Based on the results, it can be stated that high yielding KF cows are more sensitive compared to Sahiwal cows during summer season. Therefore, KF cows needs to be provided better microenvironment and improved managemental practices for normal physiology and productive performances.