Heat stress in pigs: practical strategies to protect performance during hot weather

2 April 2026

5 minute read

By: Dr. Neophytos Neophytou

High summer temperatures can quietly erode pig performance, fertility, and piglet survival. Here are the key warning signs and the most practical ways producers can reduce heat stress on farm.

Introduction

Heat stress is one of the most important environmental challenges in modern pig production, especially in regions where summer temperatures frequently exceed the thermal comfort zone of pigs. These conditions can lead to reduced productivity, reproductive problems, and increased health risks.

Understanding how pigs respond to high temperatures and implementing practical cooling strategies can help producers protect both animal welfare and farm profitability.

Why pigs are particularly sensitive to heat

Compared with many other livestock species, pigs have limited physiological mechanisms for dissipating heat, which makes them particularly sensitive to environmental heat stress (Kołacz & Dobrzański, 2019; Mount, 1979; Curtis, 1983).

Instead, pigs rely mainly on respiratory evaporation and behavioral changes to regulate body temperature. During hot conditions they may:

• increase their respiratory rate (panting)
• lie stretched out to expose more body surface
• reduce feed intake
• seek cooler or wet surfaces

When environmental temperatures rise above the pig’s upper critical temperature, the balance between heat production and heat dissipation is disrupted. As a result, body temperature increases and heat stress develops.

Early signs of heat stress

Early recognition of heat stress is essential for preventing severe production losses.

Typical warning signs include:

• rapid breathing or panting
• reduced feed intake
• increased water consumption
• lethargy or reduced activity
• pigs lying spread out on the floor
• animals crowding near drinkers or ventilation outlets

If heat stress becomes severe, pigs may show open-mouth breathing, excessive salivation, and difficulty standing. Under extreme conditions, body temperature may rise to life-threatening levels.

Effects on growth performance

One of the earliest consequences of heat stress is a reduction in feed intake.

As ambient temperature rises above the optimal range (18–20 °C), pigs reduce feed consumption in order to decrease metabolic heat production. Research indicates that when temperatures reach around 30 °C, feed intake can decrease by more than 30% (Renaudeau et al., 2011).

Lower feed intake inevitably leads to reduced daily weight gain and poorer feed conversion efficiency. Studies suggest that pigs may lose approximately 35–40 grams of daily weight gain for each 1 °C increase above the optimal temperature (St-Pierre et al., 2003).

For producers, this means that even short periods of hot weather can significantly reduce growth performance and increase production costs.

Effects on reproductive performance

Heat stress also has important effects on reproduction, particularly in sows.

During hot summer periods, producers often observe what is commonly called seasonal infertility. This phenomenon may include:

• delayed return to estrus after weaning
• reduced intensity of estrus signs
• lower conception rates
• increased embryonic mortality
• smaller litter sizes

High temperatures can also increase the incidence of stillborn piglets, especially during the final stage of gestation.

Boars are also sensitive to heat stress. Elevated temperatures may reduce semen quality, although these effects typically become visible several weeks after the heat exposure.

Impact on lactating sows and piglets

Lactating sows are particularly vulnerable to heat stress because milk production requires large amounts of energy.

When temperatures rise, lactating sows often reduce feed intake significantly. This can result in:

• decreased milk production
• increased body weight loss in the sow
• slower piglet growth
• higher piglet mortality

Heat stress may also reduce the immunological quality of colostrum, which can compromise the passive immunity of newborn piglets (Black et al., 1993).

Practical cooling strategies

Because pigs have limited physiological cooling capacity, environmental management is essential during hot weather.

Several practical strategies can help reduce heat stress in pig production systems.

1. Water sprinkling

Sprinkling pigs with water is one of the most effective cooling methods. When water evaporates from the skin, it removes heat from the body and improves thermal comfort.

In well-ventilated buildings, sprinkling systems can reduce the effective temperature by approximately 3–5 °C.

This method is particularly useful for finishing pigs, gestating sows, and boars. However, it is usually avoided in farrowing units because newborn piglets can become chilled if they are accidentally wetted.

2. Improving ventilation

Increasing air movement is another effective strategy for reducing heat stress.

Airflow improves convective heat loss from the animal’s body and helps remove excess heat and humidity from the building. For heavier pigs, increasing air velocity from about 0.5 m/s to approximately 2 m/s can significantly improve heat dissipation.

In open housing systems, natural ventilation may provide sufficient airflow when wind conditions are favorable. In enclosed facilities, mechanical ventilation allows producers to control air movement more precisely.

3. Evaporative cooling systems

Many modern pig farms use evaporative cooling systems such as fogging or misting.

These systems produce extremely fine water droplets that evaporate in the air and reduce indoor temperature. Under suitable conditions, evaporative cooling can lower air temperature by approximately 7–8 °C.

However, their efficiency depends on relative humidity. When humidity is high, evaporation becomes less effective.

4. Pad cooling systems

Pad cooling systems are another widely used technology in mechanically ventilated pig houses.

In these systems, incoming air passes through wetted cooling pads before entering the building. As water evaporates from the pads, the air temperature decreases.

Depending on environmental conditions, pad cooling systems can reduce incoming air temperature by 5–18 °C.

5. Geothermal ventilation

An emerging technology for livestock buildings is geothermal ventilation, also known as earth-air heat exchange.

In this system, incoming air is passed through underground pipes before entering the building. Because soil temperature remains relatively stable, the air is cooled during summer and slightly warmed during winter.

Studies suggest that geothermal systems can reduce incoming air temperature by approximately 4–10 °C, although installation requires careful planning and underground infrastructure.

Management and nutritional measures

In addition to environmental cooling systems, management practices can help pigs cope with high temperatures.

Useful strategies include:

• ensuring constant access to clean drinking water
• feeding animals during cooler hours of the day
• offering smaller but more frequent meals
• slightly increasing dietary fat levels to reduce metabolic heat production
• supplementing electrolytes and antioxidants

These measures can help maintain feed intake and reduce physiological stress during hot weather.

Conclusion

Heat stress represents a major challenge for pig producers, particularly during the summer months. Elevated temperatures can reduce feed intake, slow growth, impair reproduction, and negatively affect piglet survival.

Because pigs have limited natural cooling mechanisms, effective environmental management is essential. A combination of improved ventilation, water-based cooling methods, and appropriate nutritional strategies can significantly reduce the negative effects of heat stress and help protect farm performance during hot weather.

As climate variability continues to increase, implementing effective heat-stress mitigation strategies will become essential for maintaining both animal welfare and farm productivity.