Pigs are highly susceptible to heat stress due to limited sweat glands, making thermal management critical for welfare in intensive systems.
Heat stress represents one of the most significant and growing welfare threats to farmed pigs globally. In conventional intensive systems, pigs have no access to the wallowing behavior that constitutes their primary natural cooling mechanism. Panting is inefficient at high ambient temperatures, meaning pigs in poorly ventilated barns rapidly develop hyperthermia during summer heat events. The suffering of heat-stressed pigs is substantial: behavioral indicators include lethargy, open-mouth breathing, skin reddening, reduced activity, and crowding around drinkers. Pregnant sows are especially vulnerable since heat stress causes embryo death, reduced litter sizes, and compromised maternal health. Climate change projections indicate that heat stress will become increasingly severe in major pig-producing regions unless proactive infrastructure investment is made. Providing outdoor access with shade and wallowing opportunities eliminates the welfare problem while meeting pigs behavioral needs simultaneously.