Heat stress is among the most prevalent and economically significant welfare problems in commercial livestock production, affecting billions of animals annually as global temperatures rise.
Heat stress causes suffering that ranges from discomfort to death across all major farmed species. Dairy cows under heat stress show reduced rumination, elevated respiratory rates, and immune suppression — vulnerability to mastitis and other infections increases substantially. For broiler chickens, selective breeding for rapid growth has created birds whose metabolic heat production is so high that heat stress mortality events are common even in temperate climates during summer. Effective interventions include shade provision for outdoor animals, evaporative cooling and ventilation for housed animals, access to water at reduced drinking heights during peak heat, and strategic feeding schedule adjustments to shift metabolic heat production to cooler periods. Longer-term solutions require breed selection for heat tolerance and facility design improvements.