[Embryo transfer in horses--current status and future perspectives]

Although foals born after embryo transfer are eligible for registration in the majority of horse breeds, application of embryo transfer is still rare. This is mainly due to the lack of a possibility for superovulation. Uterine stage embryos can be recovered by a non-surgical flushing technique. Transfer can be accomplished by non-surgical as well as surgical methods. In contrast to the situation in cattle, most related technologies are scarcely available. Methods of cryopreservation as well as bisection of embryos are hampered by the fact that suitable embryos (morula) can be collected from the uterus only during a very short period. In vitro production of embryos by in vitro maturation, fertilization and embryo culture is currently under investigation. Progress has been made to establish ultrasound-guided transvaginal oocyte aspiration. These techniques will provide an important stimulus for application of embryo transfer in equine species and enhance our knowledge about reproductive biology in the mare.