With ICSI, the veterinarian injects a single sperm into an egg (oocyte) in a laboratory. | Photo: Courtesy Dr. Katrin Hinrichs

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