Equine Embryo Transfer

We offer two options for horse owners interested in embryo transfer. The first, most cost-effective when working with younger or middle-aged embryo donors, involves performance of the entire procedure at our facility. We allow all individuals to "settle in", perform daily teasing to monitor estrus cycles, synchronize those cycles so that the recipients "match" the donor in the stage of their estrus cycle, inseminate the donor, and 6.5 to 7.5 days later, flush the donor and transfer the embryo(s) recovered. We perform nonsurgical transfers. Some claim a slightly higher success rate with the surgical technique, but we have not found this to be the case in our hands, and so cannot justify the extra expense and stress on the recipents.  We can discuss the details of both methods and offer our recommendation after a thorough investigation of each proposed program.

The second option, most cost-effective when working with an older and/or "problem" donor much less likely to provide a viable embryo at each attempt, involves a contractual arrangement with one of the Universities or private facilities that have an entire "herd" of recipients, and offer a "shipped embryo" program. This option involves a flat up-front fee which allows several flush attempts, and embryos to be shipped. There are typically no further charges until the recipient mare is checked in foal, at which time she is purchased. The advantage of this option with an older, problem donor, is that costs are more controlled even with a large number of attempts over the course of a season, and recipient charges are fixed until the client is rewarded with a pregnancy. Another advantage is that our charges are greatly reduced, and no recipients need to be rounded up.  The down side is that we believe that results are lower with shipped embryos than with on-site ("immediate") transfer.

Flushing of the donor mare's uterus is done standing, as for other common, reproductive procedures. Two or three liters of a special, sterile media are lavaged through the uterus, in several, separate flushes, to 'stir up' and wash out the embryo(s) present. The media is run through a special filter to trap these embryos in a much smaller volume of fluid, which is then carefully searched in sterile dishes under a stereomicroscope. At seven days of age, the equine embryo is pinpoint in size, and might or might not be visible to the naked eye. Careful inspection as to the stage, condition, and quality of the embryo is performed, and the embryo then "washed" ten times in special holding media, and loaded into appropriate transfer equipment.  Until recently, superovulation with follicle stimulating hormone (FSH) was not as successful in horses as it is in cattle.  Now, there is an FSH of equine origin that is more effective, and which we have used successfully to obtain multiple ovulations (and embryos) from a single flush.

It is important that the donor and recipient mares be closely synchronized in terms of the stage of their estrus cycle at the time of transfer; within 12 hours is ideal, and within 24 hours of one another essential. This is because of a complex and sequential series of 'back and forth' chemical signals which must transpire between the embryo and the uterus, in order for the uterus to recognize that its "owner" is indeed pregnant. These signals are critical in changing the uterine program to nurture the embryo present, instead of cycling the mare back into heat. Our transfer procedure must quietly and delicately "drop" the embryo into the recipient with as little disturbance as possible in the process, in order to acheive maximal success rates.

One common concern of mare owners is that the recipient mare may "negatively influence" the quality of the offspring. Certainly the health and nutritional capabilities of the recipient mare's uterus do play a role in the growth of the fetus, and thus its health at and after birth, but the genetics are in no way affected, having already been completely programmed at the moment of conception.

There is no one part of the ET process that is particularly expensive; the total cost is the result of numerous, simple procedures, all repeated many times. In short, "a jug full of nickels and dimes". On average, young, healthy donor mares will produce a recovered embryo about 65% of the time, while older, problem mares do so only 15 or 20% of the time. Hence, one must be prepared to try several cycles with older, problem mares.

Most Registries recognize and allow the use of embryo transfer, although you should be prepared to DNA-type the sire, dam, and resulting foal, to prove parentage. Owners should thus check with both the Registry and the stallion owner, to make sure that all procedural requirements are in place, prior to commencing an embryo transfer project.

While embryo freezing is not often done yet commercially with equine embryos, we are equipped with the latest, computer-controlled embryo freezing unit, and have taught others from as far away as Australia the details of embryo cryopreservation.  Freezing of equine embryos must be done as soon as they enter the uterus (at roughly 5.5 days of age), while they are still small enough to absorb the cryoprotectant, and thus survive the cryopreservation process.  We have also performed the GIFT  (gamete intrafallopian transfer) procedure, in conjunction with a board-certified surgeon.  This technique involves transferring an unovulated, unfertilized, mature egg from a donor mare (usually one otherwise incapable of reproducing on her own) into the oviduct of a recipient mare where sperm from the chosen sire awaits.  Contact us if you have any questions about these procedures.