Sport horse breeding in the 21st century: Almost anything is possible


Advances in equine reproduction science have come a long way from the days of the traditional breeding shed, with once rare methods on their way to becoming commonplace in the sport horse industry.

New breeding methods include intracytoplasmic sperm injection (ICSI), where a single sperm is injected into an egg extracted from a mare. The embryo then develops in a lab for a week before being implanted in the mare. There’s also the use of oocyte transfer, a technique that involves oocytes (eggs) being collected from a donor mare and then transplanted into a surrogate female before being fertilised.

Embryo transfer can be done on younger mares with no interruptions to their competition and training schedules.
Embryo transfer can be done on younger mares with no interruptions to their competition and training schedules. © Erin Gilmore

But the most popular advancement is the process of embryo transfer, which allows a mare to produce multiple foals a year, while she remains in competition.

Here’s how embryo transfer works.

  1. A donor mare and stallion, who hold the genetics of the future foal, are bred.
  2. At seven or eight days of pregnancy, the embryo is flushed out.
  3. A catheter is placed through the vagina and cervix, and an inflatable cuff on the catheter provides a fluid-tight seal.
  4. A lavage fluid with surfactin (added to reduce the “stickiness” of the embryo and allow it to be extracted easily) passes down through a tubing system into the uterine lumen. As the fluid swirls throughout the lumen and drains back out through gravity, it collects the embryo, which is swept back out. The fluid and embryo pass out through the tubing system into and through an embryonic filter.
  5. When the embryo is identified under microscope, it is removed into a more enriched medium until the time of transfer.
  6. The embryo is shipped to a recipient farm where a young and healthy surrogate mare of decent size receives the embryo. That mare carries the foal to term, but it is genetically created from the donor mare and stallion.

While the process is fascinating, some may wonder why it’s necessary. Dr Katie Atwood, from Palm Beach Equine Clinic in Wellington, Florida, says it relieves much of the concern owners have about breeding their sport horse mares.

“The gestation period for a horse is 11 months, so you’re only getting one foal per year when you breed traditionally,” she said. “This process can be done on younger mares with no interruptions to their competition and training schedules.”

Horses are now being bred at an ideal reproductive age while they are still in training, which is made even more valuable by the fact that advances in equine science has prolonged the longevity of horses. While 16 or 17 was once the age of an older horse, now it’s commonly seen as the age when horses are winning in the show ring. Thanks to embryo transfer, these horses can enjoy longer, healthy careers and still produce the talent of the future.

Atwood has seen embryo transfers become popular in dressage and polo, but she has begun to see it span all disciplines. “At the start of the season, I had one farm and a few mares, but now it has quickly grown to several farms with multiple mares at each. It is really taking off because people now realize it does not remove their mares from competition.”

The process not only keeps mares competing, but it allows stallions to cross continents. Frozen fertilized embryos from working polo ponies in the US are now being shipped to Argentina where they are carried by mares and then trained by some of the best polo trainers in the world. On the flip side, semen can also be frozen and shipped to the US.

PBEC reproductive specialist Dr Katie Atwood.
PBEC reproductive specialist Dr Katie Atwood. © Erin Gilmore

“Stallions are collected, the semen is placed with an extender and high nutrient base so the sperm has something to use for energy, and then cooled slowly until it is frozen in liquid nitrogen,” Atwood said. “Once frozen, it is theoretically good forever. Last year, I bred a mare with 1991 semen and she was successfully pregnant!”

Atwood joined Palm Beach Equine Clinic in June and brought her passion for reproductive work with her to the winter equestrian capital of the world.

“I like the creating of life,” said Atwood, a Florida native and University of Florida graduate. She is currently pursuing steps to become a board-certified reproductive specialist.

“Equine medicine is intriguing, but you’re dealing with sick, unhealthy animals. With reproduction, I am working with healthy animals and making their babies, which I love!”

The clinic has added new innovations to its breeding facilities over the past year, including a hydraulic phantom mare.

“We can raise a lower our phantom with the push of a button so it can be the appropriate for the stallion,” Atwood said. “Previously, we had to bring a tractor in to raise and lower the phantom.”

The clinic has also recently incorporated the use of a SCA CASA (computer assisted sperm analyzer) system, which evaluates sperm motility (velocity and type of movement), concentration (sperm count), morphology (sperm shape), DNA fragmentation (counting of fragmented sperm), vitality (live and dead count) and acrosome reaction, which is what ultimately allows the sperm to penetrate the egg.

Palm Beach Equine Clinic

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