Effect of Heat Stress on Fertility in Cows and Buffaloes

https://doi.org/10.5281/zenodo.18169017

Abstract

Heat stress is a principal limiting factor in the reproductive efficiency of dairy production systems, especially in tropical and subtropical environments, where the high-temperature–humidity index (THI) frequently exceeds the thermoneutral range. The objective of the present investigation was to determine the impact of heat stress on fertility in cows and buffaloes under commercial dairy farm conditions, using a prospective cohort study design in Punjab, Pakistan. A population of 330 lactating cows was studied under heat-stress (THI ≥ 78) and thermo-neutral (THI < 72) conditions; physiological traits and fertility outcomes were measured. Heat-stressed animals had significantly higher rectal temperatures and respiration rates, reflecting the physiological burden of high THI. Fertility performance declined significantly under heat stress for first-service conception rate, overall conception rate, and non-return rate in both species. Heat-stressed cows also had higher service per conception rates and a longer calving-to-conception interval. The odds of conception were independently reduced by about 40% with heat stress exposure after controlling for species, parity, and body condition score. This study confirms that heat stress significantly reduced reproductive performance in dairy cows and buffaloes and highlights the importance of preventing heat stress early to protect fertility during heat challenges. Moreover, they underscore the importance of flexible reproductive management in response to increasingly prevalent climatic drivers globally