Pig Heat Stress: Welfare Impacts and Mitigation in Hot Climates

Heat stress in pigs causes significant welfare harm, reduced production, and increased mortality. As global temperatures rise, managing heat load in pig facilities is an increasingly critical welfare challenge.

Key Facts

Pigs are particularly vulnerable to heat stress because they have few sweat glands and rely primarily on respiratory panting for evaporative cooling — an inefficient mechanism in humid conditions
The thermoneutral zone for growing pigs is approximately 15-23°C; above 27°C, pigs begin showing signs of heat stress including reduced feed intake, increased water consumption, panting, and postural changes
In severe heat stress, pigs show open-mouth breathing, lateral recumbency, and can progress to heat stroke and death if not cooled rapidly
Heat stress reduces growth rates by 20-40% and reproductive performance significantly — sows under heat stress show reduced conception rates and smaller litter sizes
Cooling strategies include evaporative cooling systems (drip coolers and foggers), mechanical ventilation, provision of wallowing areas or wetting points, and dietary adjustments to reduce metabolic heat
Climate change is expanding the geographic range and seasonal duration of heat stress conditions for pig production, including in temperate regions that previously had mild summers
Outdoor pig systems in hot climates require shade structures, wallowing areas, and wetting facilities to prevent severe heat stress — without these, welfare is severely compromised

Welfare Considerations

Heat stress in pigs is a welfare emergency at high temperatures. Open-mouth breathing with visible exertion, lateral recumbency, and failure to rise indicate severe heat stress approaching heat stroke — a painful, life-threatening condition. Below this extreme, chronic moderate heat stress causes sustained discomfort expressed through inappetence, lethargy, and behavioural changes. Pregnant sows under heat stress experience particular welfare compromise: they cannot adequately cool their developing fetuses, leading to pregnancy losses and reduced litter viability. As climate change extends heat stress seasons and intensifies peak temperatures, investment in cooling infrastructure is both a welfare imperative and an economic necessity for pig production in warm climates.

What You Can Do

Support welfare standards requiring adequate cooling infrastructure in pig housing in climates where heat stress is a risk
Advocate for mandatory minimum ventilation and cooling requirements in pig housing regulations
Choose pork products from certified welfare schemes that include heat stress prevention requirements in their standards
Support research into heat-tolerant pig genetics and dietary interventions that reduce metabolic heat production
Encourage outdoor pig producers to invest in shade structures, wallowing areas, and wetting points as priority welfare measures
Back climate adaptation funding for livestock welfare infrastructure in developing countries where heat stress risk is highest
Donate to farm animal welfare organisations working on climate adaptation for livestock welfare