Pigs are highly susceptible to heat stress because they cannot sweat effectively. As climate change intensifies summer temperatures, heat stress is a growing welfare emergency in intensive pig production worldwide.
Pigs experiencing heat stress suffer distress that is visible and measurable: they pant continuously, are reluctant to move, compete aggressively for cool lying spots, and show behavioural signs of discomfort. Prolonged heat stress causes cumulative physiological damage — elevated cortisol, oxidative stress, and intestinal barrier disruption — that impairs immune function and increases disease susceptibility. Severe events cause mortality, and prolonged moderate heat stress causes weeks of reduced wellbeing. Climate change is making this problem worse: European summer temperatures regularly exceed pig thermoneutral ranges for extended periods, and systems designed for historical climates are now inadequate. Welfare audits should include summer heat management plans as a mandatory component, and producers should be required to document ventilation capacity relative to outdoor temperature extremes.