Milestone in AgCenter research: Horses treated to ovulate early give birth to healthy foals

(04/12/21) BATON ROUGE, La. — For decades, LSU AgCenter researchers have sought to alter female horses’ reproductive cycles to help them become pregnant earlier and give birth at the beginning of the year to meet the needs of the competitive racing and show horse industry.

While Erin Oberhaus, an equine physiologist with the AgCenter, had successfully caused mares to ovulate and become pregnant months ahead of Mother Nature’s schedule, no foals were born using these methods until last month.

In February, the first four foals were born using the method Oberhaus and her team developed. The foals were born in cooperation with Timber Creek Veterinary Hospital in Canyon, Texas, and with the help of a graduate student at nearby West Texas A&M University.

“As researchers, we were definitely convinced by data,” Oberhaus said. “But industry stakeholders, they want to see that there are live, healthy offspring as a result of this research.”

Or, as Dr. Gregg Veneklasen, the owner of Timber Creek, told Oberhaus, “You can show me all the data you want, but I have four feet and a nose.”

Many racing and show horse breed registries institute a Jan. 1 birthday for all foals born within a year. In competitive events involving younger horses, this creates a significant advantage for horses born at the beginning of the year, Oberhaus said.

“They’re the same age according to their breed registry, and they’re competing against each other,” she said.

However, a mare’s natural cycle leads to foals being born later in the year. In south Louisiana, mares will usually enter a period of anestrus — when they cannot ovulate and conceive — from October to early April. Because a mare’s gestation period lasts 330 to 345 days, they usually give birth no earlier than March.

In the past, breeders have changed the cyclicity of mares to allow them to ovulate and become pregnant earlier by using artificial lighting, which has proven expensive and laborious.

AgCenter researchers have been working to alter this natural cycle in other ways since the 1990s, when Don Thompson, a now-retired equine physiologist, found that the hormone prolactin could help horses end anestrus and begin ovulation.

Oberhaus studied with Thompson while completing her doctoral work, and they tested other ways of stimulating the hormone in mares so the horses could begin ovulation earlier. They found that types of drugs known as dopamine antagonists could stimulate prolactin, causing follicles to grow and accelerating ovulation.

The opportunity to use these methods to produce live foals came last year when Veneklasen, a veterinarian in Canyon, Texas, contacted Oberhaus about inducing ovulation in mares at his embryo transfer facility at Timber Creek Veterinary Hospital, where he often works with quarter horses and rodeo bucking horses.

Oberhaus and her research team drove 800 miles to Canyon, outside of Amarillo, to treat 32 horses on a cold day in late January. Of those, 28 ovulated early, and 10 had already been selected to receive embryos and become pregnant. A graduate student at nearby West Texas A&M University, Jessica Looman, assisted them and monitored the horses. Looman studied the process for her master’s degree and traveled to the main LSU campus in Baton Rouge to analyze blood samples from the horses.

The mares carried the foals through a normal pregnancy, and they needed no supplemental progesterone, a hormone produced by the ovaries, to carry to term. Seven foals from that group have been born this year.

“That was great to know, that this was a very normal ovulation that was capable of sustaining pregnancy,” Oberhaus said.

Interested in furthering Oberhaus’ work, Veneklasen offered his assistance and a stable of mares.

“This is real world,” Veneklasen said. “The babies that have been born from this project are $30,000 to $100,000 babies.”

Now Oberhaus is studying why some mares do not respond to the treatments to induce early cyclicity. She has studied some causes, including breed, age, weight and body condition, and none appears to be a factor.

Oberhaus and her collaborators are encouraged to see foals born from their research.

“This is something that’s been in research for several decades now, and foals are actually starting to be born as a result of the research,” she said. “That’s been exciting.”

Foal standing in a stall.

A foal born as part of an LSU AgCenter research project on inducing early ovulation in horses stands in a stall next to its mother. Photo by Darcy Lively, West Texas A&M University

West Texas A&M University graduate student standing behind a foal.

Jessica Looman, a West Texas A&M University graduate student who oversaw research on inducing early ovulation in horses, stands with a foal born in the research. Photo by Darcy Lively, West Texas A&M University

Oberhaus and retired equine physiologist standing in front of a horse.

Erin Oberhaus, an LSU AgCenter equine physiologist, left, has advanced research on inducing early ovulation in horses, an area that Don Thompson, a retired equine physiologist, previously studied. Photo by Kyle Peveto

4/12/2021 8:35:26 PM
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