The search for reasons and solutions for seasonal infertility in sows by Iowa State University (ISU) animal scientists includes what may be the first scientific study of insulin’s possible role inthe problem.

Aileen Keating and Jason Ross, assistant professors of animal science, estimate that seasonalinfertility costs Iowa pork producers about $60 million a year. Nationally, the losses to the swineindustry are approximately $420 million annually.

“After a long, hot summer, pigs have problems with either getting pregnant or maintaining apregnancy,” Keating says.

Other ISU scientists are studying heat stress in pigs. It was exposure to that study and Keating’sknowledge of reproductive physiology and ovarian dysfunction that triggered her interest in studyingthe possible role of insulin.

The research is supported by a grant from the Iowa Pork Producers Association (IPPA).

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Keating knew that the sows in the heat-stress study had high levels of insulin. She also knew thathigh circulating insulin levels and problems with infertility and maintaining a pregnancy are commonamong obese women.

“When women are obese, they have problems with fertility,” Keating says. “Obese women don’tovulate very well and even when they are medically induced to ovulate, their eggs are not very goodquality. In women, obesity is associated with high circulating insulin levels.”

When pigs are heat-stressed, they don’t eat much. But even though they aren’t eating, heat stresscauses elevations in circulating insulin.

“That’s the opposite of normal in any animal,” she says. “Normally, when animals eat, they have ahigh level of blood glucose and then insulin is released to get blood glucose levels back to normal. Sousually insulin goes up after they’ve eaten. But these heat-stressed animals have suppressed feedintake.”

Keating calls it a “weird physiological phenomenon” that she was interested in exploring becauseseasonal infertility is such a huge economic cost to Iowa producers.

She believes they may be the first scientists to study a potential insulin link to seasonal infertility inswine.

The $53,000, one-year IPPA grant is allowing Keating and Ross to conduct research on the ovaries ofthe pigs in ISU’s heat stress studies.

Early findings indicate that there may be changes to the pathway that makes estrogen in the ovary ofa heat-stressed pig, which could play a role in seasonal infertility.

“If you don’t have an estrogen release, you don’t have ovulation. In pigs, it’s also what’s needed forthem to display they are in heat and to be inseminated. Estrogen is also necessary for maternalrecognition of pregnancy. So when a pig has a fertilized egg, estrogen is what signals to the pig’sbody to provide support for growth and not reject the egg as a foreign invader. We want to knowmore about what’s happening with estrogen levels in pigs and the seasonal infertility issue,” Keating says.

Keating is hopeful that during the IPPA-funded study they may begin to identify therapies orintervention strategies. Additional research will be needed, including conducting trials, before anyrecommendations can be made to producers.

“In the future, we would like to be able to do some larger trials employing mitigation strategies thatare applicable to Iowa. We would like to be able to identify something that could make a differenceand do something that helps the economy. If we can come up with a kind of therapy or interventionstrategy, it could save a lot of money for Iowa producers and those around the United States and abroad. Thisis a global problem,” she says.

Find other Iowa State University College of Agriculture and Life Sciences newsreleases and related photos at

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