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Keep cool for the summer: How to treat heat stress in pigs

April 21, 2020
Heat stress in pigs

Heat and wide fluctuations in temperature can often cause immense stress for the pigs, resulting in lower performance, health problems and economic losses for the farmer.

With the numerous health and environmental challenges disrupting the pig industry at present, the summer heat is one seasonal condition that pig farmers cannot afford to let stifle their profitability. Heat stress can take a serious toll on pig performance, especially in breeding herds and finisher pigs. Heat and wide fluctuations in temperature are often immensely stressful for the animals, resulting in diminished performance, health problems and, eventually, economic losses for the farmer.

Why are pigs so sensitive to heat stress?

Pigs are extremely sensitive to changes in temperature because they do not have functional sweat glands and, therefore, do not have a way of efficiently cooling themselves. In addition, pigs have relatively small lungs for their body size, making it difficult for them to remove excess internal heat.

“Even during the hottest time of the day, pigs are still producing additional body heat from eating and moving around the barn,” said Russell Gilliam, U.S. swine business leader for Alltech. “Since pigs have few sweat glands, cooling off by perspiration is not much of an option. Respiratory rates begin to increase at around 70° Fahrenheit, and with high humidity, it becomes difficult for pigs to find relief from the heat on their own.”

Temperature fluctuations that continue from the summer into the fall season produce additional challenges. Wide variations in temperature between night and day can compound the stress that the animals already experienced as a result of increased temperatures.

What are the symptoms of heat stress in pigs?

One of the negative effects of heat stress is reduced feed intake. When pigs eat less, they convert less feed into muscle, thus reducing average daily gain (ADG) and potentially increasing their days to market. In turn, this can also lead to a heightened risk of health challenges and, ultimately, additional costs for producers.

Other symptoms include:

  • Increased respiratory rate (panting)
  • Excessive water intake and increasing loss of electrolytes
  • Reduced activity
  • Lying stretched on the floor, often separated from others

6 management strategies to reduce heat stress in pigs

Although stress cannot be completely avoided, the goal should be to minimize it as much as possible. Below are some quick tips for reducing heat stress and its negative effects:

  1. Control the temperature, and make sure the temperature only shifts a few degrees in the barn.
  2. Ensure that each pig has enough space and ventilation.
  3. Coincide feeding times with the cooler parts of the day (e.g., earlier or later in the day).
  4. Provide pigs with unlimited access to fresh and cool drinking water.
  5. Move and transport work pigs early, keep them in groups and let them set the pace. Spend time with them prior to the move to ease their stress.
  6. Tailor their diets to include technologies that will support them during stress.

Balancing temperature, ventilation and humidity

When pigs are kept at temperatures above their comfort zone, feed intake is sure to decrease, as are daily gains. In modern swine barns, pigs are at a greater risk of experiencing heat stress than cold stress. Ensure that all fans, sprinklers, cool cells and other cooling equipment are adequately maintained so that they will function properly during the hot summer months.

In addition, make sure that your barn is properly ventilated to provide pigs with an optimal environment. Even if the thermostat reading falls within the pigs’ comfort zone, what they are actually experiencing may still be stressful.

Effective temperature is a concept similar to wind chill and heat index. For example, 60°F is a favorable temperature for a 125-pound pig. However, 60°F combined with a high air speed (e.g., 100 feet per minute) would be cold and, consequently, the pig would be forced to divert energy away from growth to maintaining its body temperature. Chart 1 shows how wind speed affects temperature.

Chart 1: Effects of wind speed on temperature

Air speed

adjustment (°F)









The temperature within the barn needs to be adequately adjusted to account for the additional heat production from the growing pig. For every 60–80 pounds of gain, the pig will produce an additional 200 Btu of heat every hour, so the cubic feet per minute (CFM) must be properly adjusted to account for the increasing heat production.

Chart 2: Recommended ventilation rates, CFM per pig

Pig weight, lbs. Minimum Mild weather Hot weather

30–75 lbs.




75–150 lbs.




150–280 lbs.





Effects of humidity

Humidity is also an important indicator of proper ventilation. During warmer months, when the outside temperature exceeds the set point, increasing ventilation rates will not decrease humidity in the barn because warm air has a higher water-holding capacity than cooler air. Pigs can develop heat stress at much lower temperatures when the humidity is high, so humidity, along with temperature, needs to be carefully regulated in the barn. It is recommended to operate at a relative humidity of 65% or less, as this level of humidity will decrease condensation and wet floors in the barn.

Tailoring diets to support stress

Data has shown that offering pigs a combination of organic acids, electrolytes, enzymes and probiotics, such as those included in Acid-Pak 4-Way®, can support young animals during times of stress. Organic acids promote probiotic growth in the gut, and enzymes can help enhance intake and digestibility. Electrolytes keep the animal hydrated, especially in times of heat stress.

Addressing heat stress and being prepared for its effects can have a major impact on the performance and overall value of your pigs when you take them to market. It can also help reduce the cost of added days on feed and additional health costs. In times of stress, pigs can be more susceptible to disease and health challenges. It is essential that your pigs’ nutrition is bolstered by technologies that build their natural immunity.


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