Clinical Considerations Regarding Assisted Reproductive Procedures in Horses

Embryo transfer is widely accepted in the equine industry, but new assisted reproductive procedures and their advantages and disadvantages are less recognized. Clinical use of assisted reproductive technologies has primarily been focused on producing offspring from mares or stallions with compromised fertility. Oocyte transfer (OT) involves the transfer of a donor's oocyte into a recipient's oviduct. The oocyte does not contact the tubular genitalia of the donor mare, and various problems of the mare's reproductive tract can be avoided. Because in vitro fertilization has not been repeatedly successful in the horse, gamete intrafallopian transfer (GIFT) and intracytoplasmic sperm injection (ICSI) have been developed as methods to use low sperm numbers. For GIFT, the oocyte and a small quantity of sperm are placed in a recipient's oviduct; however, the most conservative sperm use is provided by ICSI. During ICSI, a micromanipulator is used to manually insert a sperm into an oocyte, resulting in assisted fertilization. Development of new assisted reproductive techniques has provided the equine industry with methods to produce offspring from valuable mares and stallions that are subfertile or infertile by standard breeding methods or embryo transfer. However, assisted reproduction procedures have limitations and potential risks that the equine practitioner should recognize. The aim of this manuscript is to review current clinical uses and potential complications from assisted reproductive procedures.