By Diane DeWitte, UMN Extension swine educator
Written for submission to The LAND - as June 26, 2026, Swine & U column
Summer’s here! Full sun, regular rains, the beauty of blooming flowers and growing crops, and the effortlessness of going to work in light, simple clothes. It’s the season when machinery starts for the first time, and we can work forever during the long days. The pigs generally do well in summer, both commercial herds and the special porkers headed for the county fair.
High summer temperatures can be hard on swine, though, whether they’re growing indoors in a protected barn environment, outdoors in an open-air building, or on pasture. Here are some reminders for the best care for you and your pigs through the hot season.
As a pig gets older and heavier, its ideal temperature declines. Heat stress is a greater concern in older finishing pigs (larger than 110 pounds), sows, and boars than in young pigs.
Seasonal infertility refers to the usual decline in production by sows bred during summer and farrow from November through January. Summer weather that leads to heat stress is the primary cause of seasonal infertility in the breeding herd. Heat stress also harms production in sows during lactation, when high summer temperatures reduce their feed intake. Lower feed intakes lead to depressed milk production, which reduces piglet body weight gain. Sows that experience heat stress 14-21 days before insemination may have a lower farrowing rate. If they are overheated from days prior to 12 days after insemination, their total pigs born per litter may decline.
Studies have shown that piglets born to sows that experienced heat stress during pregnancy had increased core body temperature, which made them more prone to heat stress after birth. Changes in metabolism also occurred in these offspring, which resulted in less skeletal muscle and more fat tissue being deposited during the growth stage.
If pigs become overheated, do not drench them with cold water. Instead, sprinkle with cool water, get them into shade, and allow them to recover.
The included tables show recommended ventilation rates and temperatures for pigs according to their size. Reviewing these tables when setting the controllers in a swine building can help you most efficiently dry and cool the environment.
Ag Safety & Health eXtension thoroughly explains what happens to us when we get hot. We sweat when our skin becomes warmer than the surrounding environment. The sympathetic nervous system releases acetylcholine which turns on the sweat glands and moves moisture to our skin. Evaporation of sweat on our skin cools us. When the weather is hot and humid, sweat doesn’t easily evaporate and our entire system warms up, our heart pumps harder, and we sweat excessively. This depletion of water and electrolytes from the body can lead to a heat-related illness.
Rash — Red, itchy skin bumps. Treatment includes cleaning and drying the skin and applying calamine lotion.
Cramps — Painful muscle spasms in arms, legs, or belly. Treat by drinking water, resting, and getting into shade.
Dizziness or fainting — Treat by drinking water, resting, getting into shade, and elevating legs.
Exhaustion — Vomiting or feeling sick to stomach; cool clammy, sweaty or pale skin; weak, tired, light-headed or having a headache. Treat these symptoms with water, rest, shade, elevation of legs, application of cool, wet clothes.
In each of these situations, TELL SOMEONE! Heat illness can proceed quickly and may require professional medical attention.
Written for submission to The LAND - as June 26, 2026, Swine & U column
 |
| Photo credit: National Pork Board |
Summer’s here! Full sun, regular rains, the beauty of blooming flowers and growing crops, and the effortlessness of going to work in light, simple clothes. It’s the season when machinery starts for the first time, and we can work forever during the long days. The pigs generally do well in summer, both commercial herds and the special porkers headed for the county fair.
High summer temperatures can be hard on swine, though, whether they’re growing indoors in a protected barn environment, outdoors in an open-air building, or on pasture. Here are some reminders for the best care for you and your pigs through the hot season.
Hot pigs
Pork Quality Assurance (PQA Plus) guidelines emphasize that pigs are highly susceptible to heat stress because they lack functional sweat glands. Overheating can quickly become life-threatening or degrade meat quality. Producers should monitor pigs for panting and lethargy, manage ventilation, and use cool (not cold) water to gently lower their body temperature.As a pig gets older and heavier, its ideal temperature declines. Heat stress is a greater concern in older finishing pigs (larger than 110 pounds), sows, and boars than in young pigs.
Reproduction
Heat stress begins to affect sows, boars and finishing pigs at about 70° F. If temperatures remain above 80°F for more than two to four days, decreases in performance and reproductive efficiency can result if cooling relief isn’t available.Seasonal infertility refers to the usual decline in production by sows bred during summer and farrow from November through January. Summer weather that leads to heat stress is the primary cause of seasonal infertility in the breeding herd. Heat stress also harms production in sows during lactation, when high summer temperatures reduce their feed intake. Lower feed intakes lead to depressed milk production, which reduces piglet body weight gain. Sows that experience heat stress 14-21 days before insemination may have a lower farrowing rate. If they are overheated from days prior to 12 days after insemination, their total pigs born per litter may decline.
Studies have shown that piglets born to sows that experienced heat stress during pregnancy had increased core body temperature, which made them more prone to heat stress after birth. Changes in metabolism also occurred in these offspring, which resulted in less skeletal muscle and more fat tissue being deposited during the growth stage.
Growing pigs
In response to heat stress, growing pigs will decrease feed intake to reduce the heat they make. Reduced feed intake reduces growth rate. Pigs raised in heat-stress settings will have more fat deposits than pigs raised in cooler settings. Increased fat results because the pig’s body changes how it uses nutrients. Nutrients are put towards more fat growth than protein growth in heat-stressed pigs consuming less feed.Pigs raised outdoors
Summer is the most common time to raise pigs outside, and the shelter and equipment requirements are simple. Make sure that outdoor pigs have good shade to protect them from the heat of the sun and to avoid sunburned skin on light-colored pigs. In many outdoor or pasture-based pig systems, a simple open shelter or a hay wagon provide sufficient shade under which they rest. Ensure that outdoor pigs always have plenty of fresh water available. Pigs do not sweat; they prefer to lie on a wet floor or make themselves a cool muddy wallow in which to rest comfortably.If pigs become overheated, do not drench them with cold water. Instead, sprinkle with cool water, get them into shade, and allow them to recover.
Cool places
Pigs housed inside a building produce heat, gas, and moisture. Their heat results from their metabolism and the larger they grow, the more heat they produce. Gas develops from stored manure. Moisture occurs from several sources in swine barns including:- Pigs breathing (respiration)
- Drinking water spills
- Evaporation of urine and manure
The included tables show recommended ventilation rates and temperatures for pigs according to their size. Reviewing these tables when setting the controllers in a swine building can help you most efficiently dry and cool the environment.
Managing facilities for efficient ventilation
Good building maintenance habits can maximize the effects of your careful controller settings.- Repair all leaking drinker nipples and water lines to reduce moisture in the building.
- Clean up manure and urine to further reduce both humidity and ammonia in the area.
- Remove dust from ventilation equipment, controllers, fans and air inlets.
- Clean fan blades and shrouds, and check fan motors regularly to ensure dependable operation.
- To reduce the dust in the building, limit handling of feed and disturbance of the pigs.
- Check to see that air inlets are not plugged with dust or building materials loosened by rodents.
Evaporative cooling
Forcing outside air through evaporative cooling pads built at the end of the barn uses the phenomenon of evaporation to increase the air’s humidity content and reduce its temperature. These work best during the hottest part of the day, but not as well during high humidity weather. In some cases, evaporative cooling has proven to reduce barn temperatures from 5-15° F. The cooling pads should dry out each night to reduce the chance of mold or algae growth.Take care of yourself
Farmers work in all types of weather conditions, and in many cases, will develop tolerance to the weather conditions as the seasons progress. High heat events, however, can hit quickly and require special attention to activity and fluid consumption.Ag Safety & Health eXtension thoroughly explains what happens to us when we get hot. We sweat when our skin becomes warmer than the surrounding environment. The sympathetic nervous system releases acetylcholine which turns on the sweat glands and moves moisture to our skin. Evaporation of sweat on our skin cools us. When the weather is hot and humid, sweat doesn’t easily evaporate and our entire system warms up, our heart pumps harder, and we sweat excessively. This depletion of water and electrolytes from the body can lead to a heat-related illness.
What to look for
Our friends at the Upper Midwest Ag Safety & Health Center (UMASH) remind us to know and recognize the symptoms of heat illness.Rash — Red, itchy skin bumps. Treatment includes cleaning and drying the skin and applying calamine lotion.
Cramps — Painful muscle spasms in arms, legs, or belly. Treat by drinking water, resting, and getting into shade.
Dizziness or fainting — Treat by drinking water, resting, getting into shade, and elevating legs.
Exhaustion — Vomiting or feeling sick to stomach; cool clammy, sweaty or pale skin; weak, tired, light-headed or having a headache. Treat these symptoms with water, rest, shade, elevation of legs, application of cool, wet clothes.
In each of these situations, TELL SOMEONE! Heat illness can proceed quickly and may require professional medical attention.
Recommendations to avoid heat-related problems
- Do not wait until you are thirsty — Come to work hydrated and drink approximately 8 oz. (1 cup) of water every 15 to 30 minutes.
- Take a 15-minute break in a shaded area every two hours.
- Monitor the weather and schedule strenuous work activities accordingly to reduce exposure to high heat situations.
- Wear light-colored, lightweight, and non-constricting clothing.
- Avoid the use of alcohol, drugs, caffeine, and large amounts of sugar when exposed to heat because they can increase your rate of dehydration.
- Check your prescriptions and over-the-counter medications to determine if there are any side effects when you are exposed to heat.
- Appropriately wear specialized protective gear such as cooling vests to reduce your risk of a heat illness. Note: if used inappropriately, heat illness can increase.
- Learn about prevention of heat illness and teach your team members about health and safety instructions related to working in hot weather and appropriate responses to heat-related illnesses.
- Gradually build up a tolerance to working in the heat. If a person has a severely low tolerance to heat, that person may need to perform tasks that limit exposure to heat.
- Certain types of personal protective equipment (PPE) can increase the risk of heat stress, such as protective suiting. Schedule jobs that require PPE during cooler times of the day.
- Recognize the conditions that can affect body heat such as fever, physically strenuous work, and even time of day (for example, body temperature is higher in late afternoons).
- Talk to your physician if you have a chronic health condition or disability (e.g., spinal cord injuries, multiple sclerosis) before working in the heat.
Content sources include:
- Heat-related illnesses and agricultural producers. (2024) Ag Safety and Health eXtension Community of Practice. Retrieved from https://ag-safety.extension.org/heat-related-illnesses-and-agricultural-producers/.
- Heat stress in swine affects production. https://extension.umn.edu/swine-production-management/heat-stress-swine-affects-production
Comments
Post a Comment