The hot days of summer can have significant impact on the productivity and health of all pigs as elevated temperatures often reduce the fertility of gilts, sows and boars. Research has shown that females have a prolonged return to estrus or fails to return to estrus after weaning, reducing conception rates.

Judging by the increased sow-herd culling rate from August through December, hog producers in the United States are dealing with loss of productivity (see figure to the right). In order to minimize loss of productivity and profits during the hot summer, the National Pork Board offers these tips.

Jason Ross, Iowa State University associated professor, in the last heat stress webinar presented by the NPB, recommends selecting breeding stock with production tolerant to heat stress as another tool for reducing costs that are associated with productivity loss during the summer months. Ross explains that “Seasonal infertility represents one of the most costly environmental detriments to swine production efficiency.”  

In a limited study, Ross and a team of researchers are studying the effects of heat stress on breeding stock reproductive performance. The research shows that thermoregulatory response to heat stress in gilts prior to puberty is repeatable in the future. 

He adds that endocrine markers may have usefulness in assessing the biological mechanisms that contribute to infertility in the summer. Identification of genomic regions associated with these responses to heat stress is critical in identifying animals with a production tolerance to heat stress.

Ross and the team of researchers will be continuing its research “Understanding the Biology of Seasonal Infertility to Develop Mitigation Strategies for Swine” in order to uncover more information to assist hog farmers in limiting heat stress impacts.

Ross’s presentation was the last of four webinars hosted by the National Pork Checkoff every Tuesday in August. The Checkoff’s animal science committee selected heat stress for this year's webinar series because it affects all producers regardless of farm size or location, yet producers have few tools to combat the effects of summer heat.

Recordings of the webinar are available at ww.pork.org/animalscience.