Sweltering heat of summer can have a large impact on the U.S. hog industry. Though the hogs themselves do not sweat, the producers will as heat stress makes a large economic dent in productivity.

During a Tuesday webinar by the National Pork Board, Iowa State University Animal Science Professor Lance Baumgard said ISU researchers have been emphasizing heat stress for the last six or seven years, and the webinar was based on some of the research findings.

Baumgard credits Dr. Steve Pollmann with tabulating $900 million a year loss to the swine industry, about half in the grow-finish stage and half in the reproduction stage, “so as you see this is a big economic impact on the industry,” Baumgard said, and it’s not just an American issue as he said the Chinese government has labeled heat stress the largest impediment to feeding their country.

In the United States, Baumgard said each year 10% of the herd gets porcine reproductive respiratory syndrome, “yet everyone is affected by heat stress.”

Baumgard stressed the importance of producers investing in heat abatement strategies to mitigate heat stress, though admitting it’s not feasible to air condition complete hogs barns. He did, however, suggest the potential to air condition segments of the barns where reproductive females may be housed at critical times in their reproductive stage. “That research is years down the road,” Baumgard said, “but it does make sense for producers to possibly invest more in cooling those sows at a time when they are most sensitive” to heat stress.

Climate change, genetics

Baumgard said heat stress could continue to become more of a problem if climate change continues as many predict, compounded by the industry’s continued emphasis to select genetics for leaner animals as increased muscle mass increases basal heat production. “Genetic selection for leaner traits may be an even bigger issue than climate change,” he said. “Doesn’t matter what animal we are talking about pigs, dairy cows or chickens, the more productive an animal is, the more metabolic heat it produces, and the more metabolic heat it produces, the more susceptible it is to heat stress.”

Heat stress is not just a producer issue of wide variable market weights; it also has become a packer issue with reports of “seam fat” or “flimsy fat.” Producers will also experience seasonal infertility issues due to heat stress, with females failing to express estrous, lower conception rates and failure to maintain pregnancy, and of course potential for mortality in the herd.

All species are prone to heat stress, and pigs are no exception, and what happens in the body during heat stress is a marked diversion of blood flow to the skin and extremities in an attempt to maximize radiant heat dissipation, resulting in blood flow to the gastrointestinal tract being restricted. This ultimately results in jeopardizing gut integrity, leading to lower producing pigs.

The Aug. 4 webinar was the first of four (noon CDT each Tuesday of August) webinars.

“The Checkoff’s Animal Science Committee is pleased to again bring this type of research-based information to all producers this year,” said Chris Hostetler, director of animal science at the NPB. “The subject of the series affects all producers regardless of farm size or location, yet producers have few tools to combat the effects of summer heat. However, being aware its long-term impact is the first step.”

There is no cost, but participants must register in advance by going to www.pork.org/production-topics/animal-science.

Remaining webinars

Aug. 11: Tim Safranski – Impact of in utero heat stress on subsequent growth, composition and reproduction

These results suggest that heat stress of developing embryos could have a significant effect on the subsequent performance of pigs.

Aug. 18: Shelly Rhoads – Impact of in utero heat stress on subsequent lactational performance and performance of offspring

The results of this experiment indicate that in utero heat stress has long-lasting and transgenerational effects on measurements of swine productivity.

Aug. 25: Jason Ross – Understanding the biology of seasonal infertility to develop mitigation strategies for swine

Selecting females that are heat tolerant may improve reproductive performance during the heat of summer.

These webinars originated from discussions by the NPB Animal Science Committee to identify research projects with on-farm implications and create a way to disseminate that information.

Recordings of the webinars will be made available at www.pork.org/animalscience within a few days after each specific webinar.