Cutting-Edge Reproductive Techniques for Horses

Techniques continue to be developed to aid equine reproduction. Some methods discussed at the recent American Association of Equine Practitioners conference are:

• Postmortem ovary/oocyte harvesting. If an owner wants a foal from a particular mare but the mare dies before she can be bred, her ovaries can be harvested within eight hours of death and the oocytes (eggs) can be used to produce foals.
• Oocyte recovery from a live mare. If a mare can become pregnant but has a history of not being able to carry a foal to term, her mature or immature oocytes can be harvested, fertilized in vitro, and then transferred into a recipient mare that will give birth to the resulting foal. Alternately, the oocytes can be transferred into a recipient mare and fertilized after transfer.
• Intracytoplasmic sperm injection (ICSI). In this technique, a single sperm is injected into the oocyte in a laboratory setting. Between 20% and 35% of oocytes handled in this way produce embryos, and pregnancy rates of over 80% have been reported when these embryos have been transferred into recipient mares. This is a preferred technique when limited viable sperm are available.
• Embryo freezing. Although this technique has not been extremely successful in the past, researchers at Texas A & M University have reported pregnancy rates of up to 50% when using biopsied embryos that had been frozen.