In the early days of embryo transfer, all collections and transfers were performed surgically. The cost, risk to donor animals, and aftercare have been greatly reduced through the current techniques of non-surgical embryo collection and transfer. The mare is restrained for non-surgical embryo transfer. Her tail is wrapped and held out of the way, while her rectum is emptied of feces. The vulva and perineum is cleansed with a mild soap and a sterile, large bore embryo collection catheter is passed through the vagina, the cervix and into the uterus. The inflatable cuff of the catheter is filled to ensure a snug seal against the cervix. One end of a sterile tubing set is attached to the catheter, and the other connected to a container of warmed sterile solution containing electrolytes, antibiotics and serum. A volume of about 1 liter of fluid is allowed to flow by gravity into the uterus. Through gentle massage of the uterus, embryos present within the uterus become suspended in the flush fluid which is then drained out of the uterus and passed into a fine filter dish which retains the embryo or embryos and a small volume of flush fluid.

This process is repeated with an additional 2-3 liters of fluid to ensure complete irrigation of the uterus. In the end, the fluid remaining in the filter dish is poured into a graded dish and examined under a dissecting microscope to locate the recovered embryo or embryos. Identifying and manipulating embryos under the microscope without losing anything, requires considerable practice and some manual dexterity. Once an embryo is identified, it is picked up in a fine catheter or pipette and transferred into a small volume of embryo holding medium. The embryo can be assessed with respect to its developmental stage, according to a system used by the International Embryo Transfer Society. Equine embryos can be held at room temperature for 2-3 hours but generally they should be transferred into a recipient mare or frozen as soon as possible. Once an embryo has been recovered, it will only result in a pregnancy if it is returned to another equine uterus. The uterine environment of the recipient uterus must be very similar to that of the donor, and the levels of hormones involved in pregnancy must be similar. It is for these reasons that the synchrony of donor and recipient cycles is very important An embryo may be transferred into the uterus of a recipient in one of two ways - either through a small flank incision - a surgical transfer - or through the cervix - non-surgical transfer. Surgical transfers may be performed under heavy sedation and local anesthesia. While surgical transfers can increase pregnancy rates, this must be offset by higher costs, more aftercare and possible complications. Non-surgical transfers are faster, less invasive and are virtually free of complications. In either case, attention to detail, minimizing trauma and donor-recipient synchrony are essential to maximizing pregnancy rates.

Embryo transfer is a technique where a 6-8 day old embryo is flushed from the uterus of a donor mare and is then transferred into a recipient mare or frozen to be transferred at a later date. The production of foals using embryo transfer (ET) is limited to a very small number of horses, creating little or no impact or genetic gain. One factor limiting the widespread use of ET in horses is cost. Another is the lack of commercially available embryos for sale. In cattle, ET is used extensively and creates significant economic and genetic gain for the industry. The acceptance of ET in cattle came about after embryos could be frozen, and more importantly when the evolving technology became simpler, more reliable and inexpensive, allowing technicians and farmers to transfer these embryos successfully into recipient cows.