Circadian changes in heat storage and heat loss through sweating and panting in Karan Fries cattle during different seasons

摘要

In order to find out the circadian variations in physiological responses, heat storage and heat loss, experiment was conducted on 12 female Karan Fries (KF) cattle selected from National Dairy Research Institute (NDRI) herd. Animals were further divided equally in two groups namely growing (8-12 months) and adults (18-24 months), and experiment was conducted during winter (December to January), spring (February to March) and summer (April to May) seasons. Physiological responses (respiration rate (RR), rectal temperature (RT), skin temperature (ST) and pulse rate (PR)), heat storage and heat loss through evaporation from skin (sweating) and pulmonary system (panting), dry bulb temperature (DBT) and wet bulb temperature (WBT), relative humidity, minimum and maximum temperatures, wind speed and temperature humidity index were calculated at 4-h intervals round the clock. Physiological responses (RR, RT, ST and PR) increased significantly (p<0.01) during spring and summer season. RR and PR were positively correlated with DBT. The circadian rhythmic variations in core temperatures during summer season were 1.0C and 1.4C, respectively, for adult and growing KF cattle. Heat loss through skin and pulmonary system was maximum in adult (76.8% and 23.2%) during summer at 2 pm compared to growing (73.9% and 26.1%). Heat storage was found to be maximum in adult than growing during all seasons. Heat storage increases as the intensity of solar radiation increases, and also higher is the surface area higher is the heat storage. Therefore, the experiment was conducted to study the influence of heat stress during the different periods in crossbred cattle.