University of wisconsin-madison

Embryo Transfer

Embryo transfer involves the collection of an embryo from a donor mare and transfer into a synchronized recipient mare.

Intensive management of both donor and recipient mare is required for a successful outcome of ET. Although this technology has been used in the cattle industry since the 1970's, it has only recently been embraced by horse breeder and breed registries.The basic procedure is shown at the left.

Unlike other species, the mare does not respond to hormonal treatments with multiple ovulations. Equine chorionic gonadotropin (eCG, PMSG), FSH, equine pituitary extract and immunization to inhibin do not cause ovulation of more than 1 oocyte. Because superovulation does not work in the mare, only one embryo is usually recovered with ET.

scheme for et: synchronize donor and recipient, breed donor, retrieve embryo at day 7 and put embryo in recipient mare

Like all management techniques, embryo transfer has both advantages and disadvantages. Research continues in the storage and freezing of equine embryos so that embryos can be shipped long distances or stored.

Advantage Disadvantage

Increase the annual reproductive rate in superior mares

Limit number of foals registered per year or  lifetime (breed registry restrictions)

Mares can continue performance career High costs for drugs, veterinarian fees, mare care, stud fees, registry fees($4,000-$12,000)
Obtain foals from problem and aged mares Intensive management of donor and recipient mare and maintenance of recipient herd
Immature 2 yr olds produce foals Only one embryo per cycle (cannot superovulate the mare)

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