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?
CEO
Tonisity International
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 significant decline in feed intake, especially in lactating sows, leading to reduced milk output and compromised piglet growth (Renaudeau et al., 2011). In finishing pigs, this manifests as lower average daily gain (ADG) and poorer feed conversion ratios, extending the time needed to reach market weight.
Reproductive performance also suffers. Heat stress is known to disrupt oestrous cycles, decrease farrowing rates and increase embryonic loss (Bloemhof et al., 2013). Boar fertility is also at risk, as sustained heat exposure can reduce semen quality and key fertility indicators.
Beyond productivity, animal health deteriorates. Heat stress causes dehydration and electrolyte imbalances, impairs gut function, and increases pathogen susceptibility (Baumgard & Rhoads, 2013). In piglets, particularly during the weaning period, these stresses contribute to elevated mortality and suboptimal growth rates, increasing the demand for veterinary interventions and labour.
THE REAL COST: ECONOMIC IMPACT ON PIG FARMS
Heat stress poses a substantial economic challenge to the pig industry worldwide, leading to significant financial losses at multiple levels of production. In the United States alone, annual losses are estimated to range between $300 million and $900 million, with global figures reaching into the billions.
These losses arise primarily from reduced growth rates, impaired reproductive performance, increased mortality, and the additional costs associated with managing heat stress.
One of the most immediate impacts of heat stress is a marked reduction in feed intake, which can result in decreased daily gain. This slower growth translates into lighter carcass weights and diminished market value. While St-Pierre et al. (2003) reported losses of €5–10 per pig in early studies, more recent projections for Central Europe suggest similar levels — about €5.13 per pig place annually by 2030 (Schauberger et al., 2021), consistent with losses observed in the 1980s and 1990s. However, in hotter climates or less adapted systems, field reports such as Pollmann (2018) estimate losses as high as $50 to $60 (€46–55) per pig annually, underlining the growing economic risk of heat stress.
For breeding herds, heat stress negatively affects sow fertility, farrowing rates and litter sizes, further compounding economic losses. The death of a sow during late gestation due to heat stress can represent a loss of around €1,000 when accounting for both the animal’s value and lost productivity.
Beyond direct production losses, heat stress increases pigs’ vulnerability to disease, raising veterinary costs and mortality rates. Additionally, long-term effects on offspring growth and carcass quality reduce overall herd efficiency. Producers also face higher operational expenses from investments in cooling and ventilation systems necessary to mitigate heat stress.
FIVE KEY STRATEGIES TO PREVENT AND MANAGE HEAT STRESS
One of the main strategies for managing heat stress is to combat and prevent the loss of electrolytes in pigs, as the heat stress results in dehydration, electrolyte loss (particularly Na⁺, K⁺ and Cl⁻) and acid-base imbalances that compromise cellular and gut function (Huynh et al., 2005).
Oral Rehydration & Isotonic Solutions
Hydration alone is not enough during periods of heat stress. What animals need is targeted intestinal support. Isotonic protein solutions offer both, delivering water, electrolytes and nutrients directly to the enterocytes (the intestinal cells responsible for nutrient absorption), where gut function and systemic resilience are most under pressure.
In piglets, large-scale trial data involving nearly 250,000 animals show that administering a 3% isotonic solution from day 2 to 8 of life is associated with a consistent 22% reduction in pre-weaning mortality. Under heat stress conditions, these benefits become even more pronounced.
In a Spanish farm trial conducted during a summer heatwave, piglets receiving this supplementation weaned an average of 0.71 more piglets per litter, with a 54% drop in mortality and 62% fewer fall-behinds.
The benefits extend beyond the farrowing crate. Using such solutions after weaning has been shown to increase water intake by up to 1.7 times, which is crucial when appetite is suppressed and heat load is high. This improved hydration supports gut stability and fosters a healthier microbial balance, reducing the risk of digestive disturbances at a vulnerable stage.
Support is not limited to piglets. A 2022 summer trial in Romania demonstrated that supplementation with Tonisity PxW during the first week of farrowing led to a 71% reduction in sow mortality (P=0.09) during periods of extreme heat (35–40°C). Sows showed increased water consumption and improved lactation performance, underscoring the value of early hydration and nutritional support under such stressful conditions.
Whether for young piglets or lactating sows, isotonic protein solutions provide a fast, practical tool to help animals cope with the physiological burden of heat stress, helping farms protect both animal welfare and profitability.
Environmental Interventions
Creating a stable microclimate is one of the most immediate and effective strategies to protect pigs from heat stress. Key interventions include:
• Ensuring proper ventilation to maintain airflow and regulate humidity,
• Using evaporative cooling systems such as sprinklers, misters, or cooling pads,
• Providing adequate shade and insulation to reduce heat load,
• Guaranteeing continuous access to cool, clean drinking water,
• Reducing stocking density to avoid overcrowding and help pigs manage their body temperature more effectively.
While these methods are highly effective, they can require significant investment in infrastructure, making it all the more important to complement them with nutritional and hydration-based approaches that offer rapid, cost-efficient support.
Genetic Selection
Genetic selection offers a promising route to improve pig resilience under heat stress. Research shows that traits like rectal temperature, respiratory rate and feed intake under thermal load have heritable variation, making selection possible. Some tropical-adapted lines show improved performance in hot climates and may outperform commercial lines that excel under temperate conditions (Naguy et al., 2020).
Genomic tools could make targeted selection more practical. Crossbreeding with heat-adapted local breeds is also an option to explore. Most reviews on climate resilience in livestock agree that breeding for heat tolerance is a key long-term strategy, because housing, ventilation and nutrition alone cannot fully compensate for rising temperatures due to climate change.
Nutritional Interventions
Nutrition plays a critical role in helping pigs manage heat stress. One of the key strategies is to reduce the heat increment of feeding. This can be achieved by increasing dietary fat, such as vegetable oils or animal fats, which generates less metabolic heat during digestion than carbohydrates or protein. Lowering dietary fibre and adjusting protein levels, while ensuring balanced amino acid supply, also helps reduce the internal heat burden.
Supplementing with bioactive compounds such as antioxidants (for example, vitamin E and selenium), chromium to improve insulin sensitivity, and betaine as an osmoprotectant, will support the immune response and metabolic resilience under heat challenges.
Maintaining feed intake is equally important. Offering smaller, more frequent meals during cooler periods of the day encourages consumption without overloading the digestive system. Wet or pelleted feed may also be better accepted during hot weather. And of course, access to clean, cool water is essential.
ACT NOW TO SAFEGUARD YOUR HERD AND YOUR BOTTOM LINE
With summer temperatures rising and climate volatility increasing, proactive heat stress management is not optional, it is essential. By implementing a combination of environmental, nutritional and hydration-based strategies, producers can mitigate the worst effects of heat stress, enhance animal welfare and protect profitability.
Supplementing with isotonic protein solutions, especially in early life, offers a rapid, practical step to support hydration and resilience during heat stress. When combined with long-term management practices, it helps build a more resilient, productive herd, prepared not just to survive heat stress, but to thrive in the face of it.
About Mathieu Cortyl
With over 30 years of experience in the global feed and feed additives industry, Mathieu Cortyl has had roles across Europe and the Asia-Pacific. He began in R&D at Pancosma (1991–1998), focusing on trials for pigs and cattle, then moved to a feed company in France as Swine Market Manager. In 2001, he relocated to Singapore, holding leadership roles at Biomin, Impextraco and Norel, overseeing production and regional management. From 2014 to 2016, he was Commercial Director for EMENA at Kemin, leading a 30-person team across Europe, North Africa and the Middle East. Since 2017, he has been with Tonisity International, where he held senior regional roles and board responsibilities before becoming CEO in late 2024.
