Pigs are highly vulnerable to heat stress as they lack functional sweat glands, and climate change is increasing the frequency and severity of welfare-critical heat events in pig farming globally.
Pig heat stress creates acute welfare crises that are becoming more frequent as UK summers warm. Pigs experiencing heat stress show panting, reduced feed intake, increased water consumption, and lethargy before progressing to collapse and death from hyperthermia. Unlike cattle or sheep that can respond to heat by moving into shade, indoor-housed pigs are entirely dependent on building cooling systems - ventilation failure during a heat event can be lethal within hours. Outdoor pigs with access to wallows can thermoregulate effectively through mud bathing, demonstrating the welfare value of outdoor access that extends beyond simple space provision. Climate change adaptation for pig welfare requires significant investment in cooling infrastructure and building design across the sector.