Impact of Climate Change on Farm Animals: Physiological Mechanisms, Health and Productivity, and Integrated Adaptation Strategies.

Climate change is accelerating the frequency of extreme thermal environments, threatening animal welfare, global herd productivity, and agricultural economics. Heat stress-occurring when the ambient temperature-humidity index (THI) surpasses species-specific thermoneutral thresholds-initiates physiological heat-loss cascades (panting, sweating, and peripheral vasodilation), neuroendocrine disruptions (depressed thyroid hormones, elevated glucocorticoids, and insulin dysregulation), mitochondrial oxidative stress, and gut-barrier breakdown. These systemic disruptions drive substantial performance declines: voluntary dry matter intake drops by 15-25%, average daily gain by 15-30%, milk yield by 10-25%, conception rates by 30-50%, and poultry egg output and shell integrity by 15-25%. Species-specific vulnerability is governed by intrinsic anatomical and metabolic differences, including the substantial fermentation heat increment in ruminants, the lack of functional sweat glands and heavy feather insulation in poultry, and the low cutaneous evaporative capacity of swine. Furthermore, thermal stress induces oxidative damage via free radical accumulation and alters blood composition, triggering severe immunosuppression that heightens susceptibility to mastitis, respiratory complexes, and metabolic endotoxemia. Mitigation requires an integrated solutions matrix combining environmental cooling (tunnel ventilation, pad cooling, and shade), targeted nutrition (antioxidants, organic trace minerals, osmolytes, and rumen-protected fats), genomic selection (SLICK locus and thermotolerant crossbreeding), and real-time Precision Livestock Farming (PLF) monitoring. Addressing these challenges is paramount to ensuring sustainable livestock production, animal welfare, and global food security under impending climate scenarios.