Rising global temperatures are increasing the frequency and severity of heat events that threaten farm animal welfare. Heat stress is among the most significant emerging welfare challenges in animal agriculture.
Heat stress is both a current welfare problem and an accelerating one. For high-producing dairy cows, temperatures above 25 degrees Celsius impair normal function; above 35 degrees, heat stress becomes life-threatening without intervention. The combination of high metabolic heat from milk production and inadequate ventilation in many housed systems creates dangerous conditions during heat events. Poultry mass mortality events occur regularly during heatwaves in barns without adequate cooling. Pigs, without sweat glands, are particularly vulnerable. The welfare responses — fans, evaporative cooling, sprinklers, shade for pasture animals — are known and available but require investment that not all producers make voluntarily. Climate change will make heat stress management increasingly central to farm animal welfare rather than a seasonal edge case.