Pigs cannot sweat and rely on wallowing in mud or water to regulate body temperature, making heat stress a major welfare concern in commercial pig housing without cooling provisions.
Pigs experiencing heat stress show reduced feed intake, increased respiratory rate, and behavioral signs of discomfort including skin reddening and lethargy. Severe heat stress causes hyperthermia leading to death. Pregnant sows lose pregnancies from heat stress, meaning the welfare harm extends to unborn piglets. The ability of pigs to regulate temperature through wallowing is denied in all indoor commercial systems, placing complete responsibility for thermal comfort on ventilation management that frequently fails during heat waves as climate change makes extreme temperatures more frequent.