Pigs have limited ability to thermoregulate and are highly susceptible to heat stress in summer — a major welfare concern in intensive indoor and outdoor systems as global temperatures rise.
Heat stress in pigs causes acute suffering that is clearly recognisable even to untrained observers — panting pigs crowded at water points, reluctant to move, and showing visible signs of thermal distress. The welfare impact extends beyond acute discomfort: chronic heat stress during gestation reduces placental blood flow, compromising piglet development; during lactation it reduces milk production and damages the sow-piglet bond. In finishing pigs, the combination of high metabolic heat from rapid muscle growth and external heat loading creates conditions where welfare emergencies can develop within hours. The absence of sweat glands means pigs have fewer physiological tools for managing heat than most other farmed species. Proactive cooling infrastructure — installed before summer peaks, not during them — is the most welfare-protective approach. This is both an animal welfare investment and an economic one, as heat-stressed pigs have significantly reduced growth rates and feed conversion.