Pigs are particularly vulnerable to heat stress due to their limited ability to sweat, making thermal welfare management a critical priority in warm regions.
Heat stress causes acute suffering through hyperthermia, respiratory distress, and the inability of pigs to engage in their primary thermoregulatory behavior (wallowing) in most housing systems. Pigs in outdoor systems without adequate shade and wallowing areas experience severe heat stress in warm weather. Indoor pigs in poorly ventilated buildings can experience dangerous temperature rises. The welfare harm of heat stress is compounded by the fact that pigs cannot effectively signal distress to humans through vocalisation in the way many other species can - welfare deterioration may go undetected until mortality events occur. Providing wallowing opportunities for outdoor pigs, fans and evaporative cooling for indoor pigs, and shade for all outdoor animals are essential summer welfare provisions.