By DOUG SCHMITZ

Iowa Correspondent

AMES, Iowa — For the past several years, animal scientists have been advancing their research on seasonal infertility in swine and zeroing in on its causes, giving U.S. hog producers hope for its overall management, although many components factor into the livestock malady.

“There is a lot of research happening at Iowa State and other places focused on understanding how heat stress and seasonal changes affect reproduction in pigs,” said Jason Ross, Iowa State University (ISU) assistant professor of animal science and director of the Iowa Pork Industry Center.

“Anestrous, longer wean-to-estrus intervals, and reduced farrowing rates are all components of seasonal infertility,” he added. “Understanding how heat stress alters the biological networks that regulate reproduction in pigs is a critical area of research.”

Ross said some of the key findings he and ISU researchers have found were heat stress experienced by sows during gestation alters the body composition of piglets exposed to heat stress in utero.

“Furthermore, this prenatal influence of heat stress also altered the core body temperature of piglets later in life,” he said. “Collectively, we have discovered that in utero heat stress represents a previously hidden cost on pork production.”

In fact, according to Chris Hostetler, National Pork Board (NPB) director of animal science in Des Moines, who managed a five-year research project on sow lifetime productivity and seasonality infertility, the loss of productivity because of seasonal variation continues to reduce efficiencies in pork production by roughly 10 percent and approachs an annual cost to the industry of $900 million.

Ross said he and the group of researchers have demonstrated through a series of experiments that the ovary is specifically impacted during heat stress.

“Our data demonstrate that the ovary elicits specific molecular responses to heat stress that are thought to be protective in nature,” he said. “This is an important area of understanding as it is enabling us to better understand the biological complexities the female pig utilizes in an attempt to protect the integrity of the oocytes.”

During heat stress, he said the integrity of the gastrointestinal system (GI) is also compromised resulting in a phenomenon referred to as “leaky gut.”

“Leaky gut is when the compromised GI system enables the endotoxins into the circulation of animals,” he said. “Our recent work has demonstrated that endotoxins can directly impact ovarian function in the pigs, in part explaining how heat stress influences reproduction.

“We have also demonstrated the heat stress during early gestation alters protein abundance in the ovarian and in the uterine environment during pregnancy establishment in pigs that may indicate some of the specific pathways through which heat stress results in reduced reproductive efficiency during the period of seasonal infertility,” he added.

Hostetler said when this effort to study seasonal infertility in swine was originally conceived by the NPB animal science committee in 2012, there were three priorities for research focus: Reduced nutrient use and productivity in market pigs; reduced carcass quality; and reduced breeding herd efficiency.

He said the key takeaways from this are that piglets that are gestated in sows during the hot summer months have an altered metabolism; and pigs finished during the hot summer months have a decreased ability to use nutrients because of compromised gut integrity.

“So not only do pigs eat less when they are hot, the nutrients that they do consume are not utilized properly,” he said.

Right now, as far as what producers can do to improve seasonal infertility, Hostetler said that is limited to adding cool pads to the ventilation of sow farms and air conditioning to boar studs. 

“I know there is at least one production system that has added air conditioning to their new construction sow farms and this may catch on for two reasons: The currently available technology on air conditioning is dramatically more energy efficient than what was available five to 10 years ago; and producers can now better use “off grid” energy sources (i.e., wind, solar or methane capture),” he said. 

 “I think we also have a much better understanding of the underlying biological mechanisms of heat stress that reduce breeding herd as well as market hog efficiencies.” 

“This is key in developing mitigation steps going forward,” he said. “Unfortunately, this area was underfunded and we could not garner a critical mass of funding to effectively move the needle during the five-year span (2012-17) of this effort.”

Ross said gene editing of livestock to improve their heat resilience is also an option scientists are investigating – although it’s not currently approved for human consumption.

“Engineers are also investigating improved facility designs that could mitigate the effects of heat stress and seasonal infertility.”

ACCORDING TO Chris Hostetler, the loss of productivity due to seasonal variation continues to reduce efficiencies in pork production by roughly 10 percent and approaches an annual cost to the industry of $900 million.

(Courtesy of Iowa Pork Producers Assoc.)