Asian Journal of Current Research

Climate change is increasing the frequency, duration and nocturnal persistence of thermal stress in cattle production systems, while also altering water availability, forage quality, disease pressure and the reliability of seasonal breeding environments. Reproductive adaptation therefore cannot be reduced to heat tolerance alone. It is the capacity of females, males, embryos and production systems to maintain acceptable fertility under changing climatic exposure without creating disproportionate costs in animal welfare, resource use or genetic diversity. This critical narrative review synthesises evidence published from 1 January 1987 to 30 May 2026, identified through live searches of PubMed/MEDLINE, PubMed Central, Crossref-linked scholarly records, open scholarly web indexes, citation chaining and authoritative institutional sources. The evidence indicates that reproductive failure under heat load is generated by interacting systemic, cellular and management pathways. In females, altered neuroendocrine signalling, impaired follicular steroidogenesis, oxidative and mitochondrial injury to oocytes, reduced uterine receptivity and early embryonic loss create both immediate and carry-over effects. In bulls, disrupted scrotal thermoregulation produces delayed deterioration in spermatogenesis, chromatin integrity and fertilising competence that routine semen assessment may underestimate. Genetic variation in thermoregulation and fertility reaction norms is substantial, but selection for thermal resilience is constrained by antagonisms with production, incomplete phenotyping and genotype-by-environment interaction. Cooling, shade, altered breeding calendars, nutritional support, timed breeding and embryo transfer can reduce losses, yet their effectiveness depends on climatic severity, infrastructure, water and energy availability, and the biological stage protected. The strongest adaptation strategy is therefore layered: climate-responsive management should be combined with reproductive technologies, robust phenotyping and breeding goals that protect fertility, longevity and welfare. Evidence remains weakest for long-term reproductive outcomes in beef and extensive systems, male-mediated transmission of heat damage, cross-generational effects, and the economic and environmental performance of integrated adaptation packages.