Ovine/Caprine Embryo Transfer

Embryo transfer in small ruminants is done a bit differently than in horses and cattle, in that the procedure must be performed surgically for good results. It is, however, a relatively quick and minor undertaking, which may be done with the aid of a laparoscope, minimizing incisions to just a centimeter or so.

Goats, and particularly sheep, have a very tortuous cervix which does not lend itself to easy negotiation with a catheter. In addition, they are too small to allow manual palpation and manipulation of the uterus during a flush procedure. Like cattle, however, both species respond well to superovulation programming with FSH, and typically provide many embryos per flush. Insemination of the donors may be performed by laparoscopic AI (both species); vaginal AI (goats only; results are not very good with this technique in sheep); or natural breeding.

Synchronization of donors and recipients is best performed using temporary vaginal implants, a simple and painless procedure.

Embryo recovery from donors is performed by surgical flushing of the uterus using a small, Foley-type catheter with an expandable "balloon", which acts as a seal in the uterine body, preventing escape of flush fluid and embryos except through the catheter and into a waiting receptacle. This is done under a short-acting general anesthetic, with an endotracheal tube and oxygen supplementation in place.

Recovered embryos are transferred via laparoscope into recipients that are just sedated and given two "spots" of local anesthetic. Using special forceps which do not close completely, the uterine horn adjacent to the ovary with an active corpus luteum is gently elevated to the skin surface through a small incision, and the embryo(s) "injected" directly into the lumen. This method of transfer takes no more time than the nonsurgical method commonly used in cattle.

One additional difference between embryo transfer in small ruminants and cattle, is that sheep and goats frequently have twins, and so we can implant two or even three embryos into a single recipient. We are not worried about "freemartins" in small ruminants much; that situation being peculiar to the bovine species. (In cattle, twin calves of opposite sexes creates a situation where the bull calf is normally fertile, but the heifer calf lacks proper reproductive development, due to in-utero exposure to her twin's testosterone, and is sterile).

Proper and comfortable handling of recipients utilizes custom-made "cradles" which hold and tilt the animals at an angle best suited to quick performance of the procedure. For best results, such work should be done during the natural breeding season. Embryo transfer and laparoscopic AI "out of season" is always less successful.

As with cattle, small ruminant embryos are easily frozen with our computer-controlled freezing device.