Don’t Sweat Heat Stress

( National Pork Board and the Pork Checkoff )

By Brent Sexton, DVM, Pipestone Veterinary Services

Summer means increased risk of heat stress and heat exhaustion. Heat stress is an economically important issue and can have severe consequences if proper precautions are not taken. However, through a variety of management techniques, we can help reduce the risk of our hogs being affected by heat stress.

Pigs can’t sweat, which makes them more susceptible to heat stress. Additionally, due to their relatively small lung capacity, pigs cannot effectively control their internal temperature by panting during significant heat exposure. Traditionally, wallowing in mud was the pig’s most effective means of controlling heat. This isn’t possible with modern production practices so we must rely on the facilities to keep pigs cool and comfortable. 

The impacts of elevated temperatures start as early as 70° Fahrenheit. As the temperature climbs, the pigs’ respiration rate increases and they may start actively panting. When barn temperatures climb into the 80’s, pigs may start eating less and adjust their eating patterns, consuming more feed at night. This change can potentially contribute to health issues like hemorrhagic bowel disease and ulcers. Other signs of heat stress include lethargy, open mouth breathing, discomfort, blotchy skin and poor production performance. If severe heat stress occurs, pigs can die rapidly from heat exhaustion.

To reduce the impact of heat stress on growing hogs, take a multifaceted approach to mitigate heat and deal with the heat stress that does arise. 

Ventilation is the most effective tool available to producers. Exact recommendations will vary widely between barns – but in general, the more air we move, the better. Air movement allows us to move air from outside the barn to replace the hot, humid air inside the barn. This is beneficial, even with extreme outside temperatures. Tunnel-ventilated barns are especially well suited to maximize air flow through a barn. Circulating fans can effectively move air within a barn, helping to remove heat from the hogs. Circulating fans should be used in addition to proper ventilation, not in place of it. 

Sprinklers are another excellent tool in managing heat stress. Sprinklers are notorious for clogging, so they should be inspected often. A good rule of thumb is that after the sprinklers shut off, the pens should be dry before the sprinkler turns back on again. This maximizes the evaporative cooling effects of the misters.

Cool Cells
Although more common in sow units, cool cells can occasionally be found in finishing barns. The water in the cool cell reduces the air temperature by evaporative cooling. The hot outside air is pulled through the cool cell and the cool air enters the barn. These can successfully drop the air temperature by 20° or more.

Water is a vital part of heat control. As the temperature increases, pigs will consume more water. Cool water helps to reduce the pig’s internal body temperature, as well as replace the water lost from respiration that is elevated during periods of heat stress. Market hogs should have plenty of access to water. Ideally, there should be one drinker space for every 15 market hogs, and there should always be at least two water sources in each pen. Drinkers should be checked every day for adequate water flow. Clogged drinkers and drinkers with reduced flow rate can have profound negative impacts on growing pigs. Ideally, growing/finishing pigs will have access to water with a flow rate of 2-3 cups per minute.

Emergency Ventilation Equipment
Perhaps the most important step in reducing the risk of heat stress is the emergency ventilation equipment. Test alarms, emergency curtain drops, back-up generators, etc., on a regular schedule to ensure they are all properly functioning. If the emergency system is not functioning correctly, you may have a catastrophe on your hands in a very short amount of time.

Heat stress is a very real, and significant, issue that producers must be prepared to face. Making sure your barns are ready for the increasing temperatures is the first step. If you have questions or need help, contact your veterinarian or our swine specialist team.

Dr. Brent Sexton grew up on a farm near Rockwell City, Iowa. He was active in both 4-H and FFA which he credits for his desire to become a veterinarian. Brent attended Iowa State University where he completed both his degree in animal science and his degree in veterinary medicine. His primary interests are infectious swine diseases, diagnostics interpretation and swine production. 

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