Impact of Heat Stress on Animal Reproduction and Mitigation Strategies: A Comprehensive Review

Abstract

Heat stress is a major environmental constraint affecting livestock productivity, welfare, and reproductive efficiency under changing climatic conditions. When environmental heat load exceeds an animal’s capacity for heat dissipation, coordinated physiological, endocrine, metabolic, cellular, and molecular responses are altered, with adverse consequences for fertility in both sexes. In females, elevated temperature impairs follicular development, oocyte competence, oestrous expression, fertilisation, embryo survival, pregnancy maintenance, and foetal development. In males, heat stress interferes with testicular thermoregulation, spermatogenesis, testosterone production, libido, and semen quality, including sperm motility, viability, morphology, and DNA integrity. These effects are mediated primarily through oxidative stress, endocrine disruption, mitochondrial dysfunction, apoptosis, inflammation, altered blood flow, and heat shock protein responses. Susceptibility differs among livestock species and breeds, with high-producing dairy cattle, buffaloes, and swine being particularly vulnerable, whereas many indigenous sheep and goat breeds show greater adaptive capacity. Mitigation requires integrated management rather than a single intervention. Environmental cooling, adequate water provision, nutrient-dense diets, electrolyte and antioxidant support, timed artificial insemination, embryo transfer, genetic selection for thermotolerance, and precision monitoring systems may help reduce reproductive losses. This review synthesises the mechanisms, species-specific effects, economic implications, and practical mitigation strategies associated with heat-stress-induced reproductive dysfunction in livestock under current and future climate pressure.