Summer “stall-out” is a common problem for the U.S. pork industry, but you can take steps to avoid it.

The first thing a heat-stressed pig does is step away from feed, says Bob Thaler, South Dakota State University swine specialist. In one estimate, a temperature increase causing a 20 percent reduction in feed intake will increase days to market by 29 days and cost more than $10 per pig in losses.

There are two strategies to help keep pigs performing in the summer, he says. The first is to make dietary adjustments to help minimize heat stress. Once heat stress climbs, the strategy switches to helping the pig lose heat and feel cooler.

“Pigs require grams per day of nutrients, not percentages,” Thaler notes. “Percentages are used to make feed mixing easier for people. When the pig eats adequate amounts of feed, it will reach its required daily amount of each nutrient. However, as feed intake decreases with heat stress, you’ll need to increase the percentage of nutrients to ensure that the pig is still getting the necessary grams of nutrients each day.”

For example, if daily feed intake drops from 7.2 to 6.4, pounds, you’ll have to increase the dietary lysine level by 13 percent for the pig to consume the same amount of daily lysine. Energy levels also need to be increased, and the easiest way to do that is to add fat.

Finally, research at various universities has shown that feeding ractopamine will significantly reduce the effects of heat stress on finishing pig performance.

As temperatures climb, you need to focus on cooling the pig. First, increase ventilation rates to pull the heat off of the pigs. But once it gets to 80°F, increased ventilation must be coupled with evaporative cooling to keep the pig cool. Intermittent sprinkling is the most effective way to cool grow/finish pigs; drip cooling is most effective for sows.

“A rule of thumb is to let the sprinklers run for one minute, then be off for 14 minutes to allow the water (and heat) to evaporate off of the pigs,” Thaler says. “If sprinklers are left on continually or foggers are used, the air becomes so humid that little water will evaporate from the pigs.”

Another way to think of it is that sprinklers should come on just before the floor becomes dry again. Drippers on sows can run continuously since it is a much smaller amount of water and will not significantly increase humidity in the barn.

Lastly, cool cells are an option, but Thaler adds that it’s only economical with sows. In areas of low humidity, cool cells can lower air temperature by more than 15°F.

With proper dietary adjustments and management changes, heat stress in pigs can be handled successfully most of the time.