Three Assisted Reproductive Techniques for Subfertile Mares

It can be both disappointing and frustrating when a prized mare has difficulty conceiving a foal. But, as one equine reproduction specialist reported recently, researchers have made great progress in helping subfertile mares, and owners shouldn’t give up too easily.

Katrin Hinrichs, DVM, PhD, Dipl. ACT, of Texas A&M University College of Veterinary Medicine & Biomedical Sciences, described some of the reproductive techniques veterinarians use in her presentation at the 2016 American Association of Equine Practitioners Convention, held Dec. 3-7 in Orlando, Florida. Hinrichs is a professor and Patsy Link Chair in Mare Reproductive Studies in the Departments of Veterinary Physiology and Pharmacology and Large Animal Clinical Sciences.

Intracytoplasmic Sperm Injection (ICSI)

With this technique, the veterinarian injects a single sperm into an egg (oocyte) in a laboratory. The fertilized oocyte can then grow in culture into an embryo, which can be transferred to a recipient mare. The procedure requires the practitioner to collect oocytes from the donor mare via transvaginal follicle aspiration (TVA), procedure that involves placing a needle through the mare’s flank. Usually, the veterinarian collects immature oocytes on a fixed schedule, recovering several oocytes at once. Mares that produce viable oocytes, yet suffer from conditions such as uterine adhesions, uterine infection, or recurrent anovulatory follicles might benefit most from ICSI, she said.

Oocyte Transfer

This procedure also involves collecting oocytes via TVA, but in this case, the oocytes have matured in the mare’s ovary prior to aspiration. Gathering mature oocytes requires hormone treatment and monitoring and usually only yields one oocyte. The veterinarian then transfers it surgically to the recipient mare’s oviduct (aka fallopian tube) and then artificially inseminates her. She conceives and carries the foal. Oocyte transfer is an option for producing foals in regions where ICSI laboratories are not available.

Cloning

Owners might opt for cloning to produce a young, fertile filly with the same genetics as the original donor mare. Assuming the subfertile mare’s reproductive limitations are not genetic, the cloned filly could go on to a successful breeding career, passing on the desired genes. However, very few laboratories perform cloning; it is expensive; and many breed organizations do not permit registration of cloned foals or their progeny.

Finding a Good Laboratory

If you choose an advanced reproduction technique such as ICSI, take time to identify an established laboratory that handles oocytes with proven success. It is important that a lab have a record of producing viable blastocysts (transferrable embryos). For the veterinarian, it takes practice to master the TVA procedure, so experience and training with a skilled mentor is essential.

Take-Home Message

“Assisted reproductive techniques offer tools for veterinarians and breeders alike who want progeny from valuable mares that are otherwise unable to conceive,” Hinrichs said. “Oocyte transfer, and the ICSI techniques that have been developed over the last ten years now make this possible.”

Timing, skill, and proper understanding of the subfertile mare’s underlying reproductive problem are essential. With good clinical practice and proper oocyte handling, the probability of producing a foal increases dramatically.