HORMONAL CHANGES IN HEAT-STRESSED MURRAH BUFFALOES UNDER TWO DIFFERENT COOLING SYSTEMS

Abstract

An experiment was carried out on twelve lactating Murrah buffaloes during early lactation of 50-70 days in the Cattle Yard of the National Dairy Research Institute, Karnal. Six buffaloes were kept under water showers (Group 1) while another group of buffaloes were allowed to wallow in a water pond (Group 2) from 11.00 A.M. to 4.00 P.M. daily for a period of 30 days. Blood samples were collected from buffaloes of both the groups at 3 day interval on day 1, 3, 6, 9, 12, 15, 18, 21, 24, 27 and 30 of the experiment and analysed for plasma thyroxine (T 4 ), triiodothyronine (T 3 ), cortisol and insulin hormones. The thermal humidity index (THI)s was 80.3 and 83.6 during the hot-dry and hot-humid seasons, respectively. During the hot-dry season, average plasma T 4 and insulin levels were significantly (P<0.01) higher in Group 2 as compared to Group 1. Plasma T 3 levels did not vary significantly in Groups 1 or 2. Plasma cortisol concentration in Group 1 was higher (P<0.01) in comparison to Group 2 buffaloes (4.80 vs. 2.60 ng/ml). During the hot-humid season, average T 4 , T 3 and insulin concentrations were significantly higher (P<0.01) in Groups 2 buffaloes than in Group 1 buffaloes. The overall average value of cortisol was higher in Group 1 when compared to Group 2 buffaloes. Feed intake and milk yield was significantly higher in Group 2 than Group 1 buffaloes during the hot-dry and hot-humid seasons, indicating the beneficial effects of wallowing as opposed to water showers.