Keeping mature pigs cool in summer as well as during transitional weather months is a challenge, as pork producers know all too well. But there are a few tips for improving the chances of successful cooling. 

It is imperative to know the basic principles of cooling pigs, including when to use water-evaporation options. Pigs don’t sweat, so they don’t have the built-in capacity for that cooling method, even though the evaporation process can be highly efficient in many conditions. There are some ways we can make up for the pig’s lack of sweat glands, however, and thereby keep the pig fairly comfortable and productive even in hot weather.

Priority one is air exchange through the building. Outdoor air usually has some capacity to absorb moisture, plus the outdoor air is often a little cooler than indoor air where pigs are giving off heat. So we need to bring lots of outside air into the building as the first step in cooling. 

Air-exchange rates of up to 150 cubic feet of air per minute per pig for finishing pigs and as much as 500 cfm per head for lactating sows are commonly recommended in hot conditions. Obtaining these high air-exchange rates depends on correct initial design and then on continued maintenance of the system to keep the airflow at the original design value. 

Priority two is air speed over the pig. Cooling pigs requires convection or wind chill. Few large swine barns are optimized for natural ventilation during hot periods, so depending on wind blowing through the building to cool pigs is not a realistic option. You have to provide artificial wind using electric fans; the selection and placement depends on the building’s layout and whether the structure is set up for natural ventilation or mechanical ventilation. 

The simplest circulation fan layouts will allow fan spacing of about 10 times the fan diameter. So, for 24-inch-diameter fans, you can space them about 20 feet apart and get fairly good air speeds at the pig level.  Keep in mind that this can involve a lot of fans, and not all building wiring systems are adequate to handle the loads imposed.

Priority three is the water-evaporation strategy. In all areas but the arid Southwest, there are two effective methods for this:

  • Put liquid water directly onto the pig’s skin where it can evaporate and draw heat from the body.
  • Use water evaporation to cool incoming ventilation air for the entire room. 

Either method requires supplementing air speed over the pigs via electric fans. For the first method, the skin-wetting strategy, it’s important to use nozzles or drippers that produce large water drops, not a fine mist. The idea is to produce a rain, not a fog. The water drops must wet the pig’s skin thoroughly so that the pig’s body heat can be removed effectively to maximize the amount of evaporative cooling. You can’t cool pigs with evaporative cooling if water in the pigs’ microenvironment won’t evaporate. An automatic controller that monitors room temperature and manages water on/off timing is essential, and automation easily pays for itself.

For the second method, using evaporative cooling of the incoming ventilation air, most producers use evaporative-cooling pads and can get a drop of a few degrees in the dry-bulb temperature of the air entering the room. For this method to be effective, you must have the first and second cooling priorities covered — plenty of air exchange with the outside air and good air speed at the pig level.

A well-designed tunnel-ventilation system usually can produce comfortable conditions on all but the hottest days, but systems can fail to cool if they are not maintained and operated carefully. For more information, consider getting a copy of the Midwest Planning Services’ document (MWPS-32), Mechanical Ventilating Systems for Livestock Housing or call MWPS at (515) 294-4337.