ISSUE FOCUS 68 FEED & ADDITIVE MAGAZINE July 2025 HEAT STRESS IN PIGS: WHY IT MATTERS AND HOW TO MANAGE IT Mathieu Cortyl CEO Tonisity International Heat stress in pigs poses a significant threat to welfare, performance and farm profitability. Pigs’ unique physiology makes them especially vulnerable, impacting feed intake, reproduction and mortality. Immediate and long-term effects span from reduced daily gain to increased susceptibility to pathogens. With climate volatility rising, managing heat stress requires more than ventilation—nutritional, hydration, and genetic strategies are proving critical. But which ones work best? As summer heatwaves grow more frequent, pig producers face rising pressure to reduce heat stress risks. High temperatures endanger swine welfare, performance and profits. Understanding how heat stress works and how to fight it is key to protecting both animals and farm income. WHY ARE PIGS SO SENSITIVE TO HEAT? Pigs are particularly vulnerable to heat stress because they lack functional sweat glands and have thick fat layers that hinder heat dissipation. Unlike many other species, pigs rely on panting and behavioural changes to regulate body temperature, mechanisms that become ineffective in hot, humid conditions (Brown-Brandl et al., 2004). The thermoneutral zone, the ambient temperature range where pigs do not need to spend extra energy to cool or warm themselves, varies by production stage. When pigs are outside this range, particularly in warmer conditions, metabolic performance and immune responses deteriorate. HOW HEAT STRESS AFFECTS PERFORMANCE AND HEALTH The effects of heat stress are both immediate and long-term. One of the earliest indicators is a Lactating sow Gestating sow Mature boar Newborn piglet Weaned piglet (below 12 kg) Post weaning (12-25 kg) Fattening (25-35 kg) Grower - Finisher 10-21 10-21 10-21 32-38 24-30 21-27 15-21 10-21 Stage Thermoneutral Zone (°C) Table 1. Optimal Thermoneutral Zones by Production Stage (adapted from the Pork Industry Handbook, Purdue University)
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