In a study from the University of Saskatchewan, Canadian researchers compared ovulation rates, embryo recovery and quality, and subsequent pregnancy rate using two estrus synchronization methods–prostaglandin (PG) administration and progesterone and estradiol (PE) administration–both combined with equine follicle-stimulating hormone (eFSH) treatments. Tal Raz, DVM, presented the researchers’ findings at the 51st Annual American Association of Equine Practitioners Convention, held in Seattle, Wash., Dec. 3-7, 2005.

Embryo transfer allows owners to maximize the number of foals from a particular mare, and can be useful when it is not desirable or possible for a mare to carry a foal full term.

Single embryo recovery attempts are common in equine embryo transfer and on average resulted in a 50% recovery rate. Recovering embryos from multiple ovulations or superovulation is less common because superovulating mares is problematic. Equine pituitary extract has been used to stimulate multiple ovulations in mares, but is not commercially available. Previous studies have shown a purified pituitary extract product called eFSH has been successful in donor mares, but little information is available on the combined use of eFSH with estrus synchronization protocols in terms of time to ovulation, embryo recovery, and post-transfer pregnancy rates.

During embryo transfer, donor and recipient mare ovulations need to be closely aligned to optimize survival of the transferred embryo in the recipient. The close alignment in ovulation is required because the recipient mare’s uterus has to be at the right stage to receive the donor’s embryo. Raz’s study focused on the process of getting donor mares ready for breeding and ovulation, in hopes of finding a method that was reliable, predictable, and cost effective