Impact of heat stress on reproductive performance of Sahiwal cows

Abstract

The objective of the present study was to investigate the effect of temperature humidity index (THI) and indicator of heat stress on reproductive performance i.e. calving interval, conception rate and pregnancy rate of Sahiwal cows maintained under Livestock Research Center, National Dairy Research Center, Karnal. A total calving record pertaining to 3000 lactations of 847 Sahiwal cows, spread over 26 years from 1990 to 2015 from were considered for the present study. The daily ambient temperature and relative humidity records were collected from Central Soil Salinity and Research Institute, Karnal and NICRA center (Climate Resilient Livestock Research Center), NDRI, Karnal. All statistical procedures were performed using SAS Statistical Package. A univariate logistic regression model was fitted to assess the effect of independent variable THI on the dependent variables conception and pregnancy status. A distinct relationship between THI and calving interval was observed in the present study, the cows had a significant longer calving interval at high THI as compared with low THI. It was observed that the average calving interval was increased by 2 days with per unit increase in THI value. Pregnancy rate and Conception rate of Sahiwal animals was significantly reduced from 35% at low THI to 18% at high THI and from 55% at low THI to 26% at high THI respectively with decreasing odd ratio. In conclusion high environmental temperature reduces the reproductive performance of animals and significantly influences the animal productivity.