EFFECT OF THERMAL STRESS ON HSP 72 AND LEPTIN mRNA EXPRESSIONS IN PERI-PARTURIENT DAIRY COWS

In order to establish the relationship between expression of Hsp72 and leptin gene, 10 each of high and low producing periparturient Sahiwal and Karan Fries cows were selected from the Institute herd during summer and winter season. Blood samples were collected from both the breeds of cattle on -45, -30, -15, 0, 15, 30 and 45 days with respect to parturition during both the seasons. HSP72 gene expression was significantly higher in lymphocytes of high producing Karan Fries and Sahiwal cows compared to low producing groups during both the season, but the magnitude of increase was higher during summer than winter. Before calving, leptin gene expression in lymphocytes of low producing Sahiwal cows was higher than high producing Sahiwal and KF cows. Whereas on the day of calving, leptin gene expression decreased in both the breeds and remain lower up to 45th day of postpartum. The relative leptin mRNA expression in high and low yielding Sahiwal cows decreased to 89.3 and 80.7% on 15th day of calving during summer season, whereas in Karan Fries the values decreased to 84.6 and 79.5% on the day of calving and 15th day of postpartum from the pre calving values (45 day) respectively. Leptin and HSP72 mRNA expression were negatively correlated to each other in both the breeds, seasons and groups. Based on the results of the present study it can be concluded that, lower levels of leptin and higher levels of HSP72 during and after parturition compared to prepartum indicates the stress on the lactating cattle. Keywords: HSP72, Leptin, Karan Fries, Sahiwal, Thermal stress