Assisted Reproductive Techniques in the Horse

Embryo transfer is commonly performed in equine practice, both to increase production from a given mare and to obtain offspring from mares that suffer early embryo loss. Oocyte transfer is a more specialized technique that is used clinically to obtain offspring from mares that cannot provide an embryo for embryo transfer. Gamete intrafallopian transfer (transfer of both sperm and oocyte to the oviduct) is currently only efficient when fresh semen is used, and so has limited application at this time. Intracytoplasmic sperm injection offers a method for in vitro fertilization of isolated oocytes, as standard in vitro fertilization is not repeatably successful in the horse. Oocytes fertilized by sperm injection can be cultured in vitro to the blastocyst stage, and then transferred transcervically to recipient mares for normal pregnancies. Foals have been produced by nuclear transfer (cloning); this offers a method for preserving the genetics of valuable individual horses.