Gardeners speak of heirloom seeds for the genetic preservation of a plant species. Horsemen selectively breed, thus preserving a mare’s bloodlines. But when the mare dies or must be euthanized, that genetic pool normally dies with her.
Scientific advances can now come to the rescue, though the cost—at least $1,975 up to when the egg meets the sperm—can be prohibitive for many owners. In layman-speak, this genetic rescue means the dead mare’s ovaries can be removed, then processed, an egg “bred” in a petri dish, then transferred to a recipient mare to carry the foal.
Jennifer Hatzel, DVM, MS, Dipl. ACT, is a theriogenologist—a veterinarian specializing in reproduction—at Colorado State University’s Equine Reproduction Laboratory, in Fort Collins. She explained to attendees of the 2016 American Association of Equine Practitioners convention, held Dec. 3-7 in Orlando, Florida, that a successful outcome depends on many elements, from the mare’s age and illness to the careful handling and shipping of oocytes.
Here’s the process. The clock starts ticking the moment the mare dies. The ovaries need to be removed ASAP and arrive to the assisted reproductive technology facility within six to eight hours for the best chance at success. With the mare on her side, the veterinarian makes an incision halfway between her last rib and her hip. Carefully avoiding the bowel, the veterinarian reaches into the abdominal cavity, finding each ovary and cutting it out.
Next, the veterinarian rinses the ovaries with room-temperature embryo flush solution, saline, or lactated Ringer’s solution and places them in a secure plastic bag with a small amount of solution to keep them moist, double-bagging to prevent leakage.
The most challenging part (and most dangerous for the eggs) is ahead, with the time- and temperature-sensitive trip to the lab that will process the oocytes. Imagine transporting human organs for transplant, and you get the idea.
Those eggs must be maintained at a stable temperature, so flights and counter-to-counter arrangements are crucial. Colorado State University and Texas A&M University have been at the forefront of offering services for postmortem ovary processing and ICSI procedure (intracytoplasmic sperm injection, the fertilization method used with these cases), so those are the two locations most familiar with all the pieces coming together in the right timing.
While this is happening, the owners should be selecting a stallion and making arrangements for his semen to be shipped. Either frozen or cooled/shipped semen can be used, but it must arrive by—at the latest—the day after the ovaries themselves arrive at the facility.
When the ovaries arrive, someone at the lab processes them so the immature eggs can mature, and then performs the ICSI procedure. That embryo is cultured, and when developed enough, it is sent for embryo transfer or frozen for later transfer.
Twenty years ago, this would have been unheard of. Though it’s still a specialty service, an increasing number of veterinarians are aware of its development and able to assist their clients should the need arise.