Embryo Transfer Services

Embryo transfer services are available Feb. 1-July 1 every year. After July 1, donor mare management is still available, but any embryos recovered require shipment to another facility for transfer into a recipient mare or frozen for transfer in a subsequent year. The owner of the donor mare is responsible for identifying the facility and acquiring a shipped embryo contract for embryos to be transported to another location. If you anticipate breeding your mare later in the season, please call us at (970) 491-8626 to discuss embryo transfer management options.

Annual embryo transfer enrollment fee of $750 is due with the signing of your contract for use of Equine Reproduction Laboratory/RME-leased recipient mares. This non-refundable, non-transferable fee enrolls the selected donor mare for the breeding season of Feb. 1-July 1. One annual enrollment fee is required for each donor mare/owner/lessee/embryo combination for the breeding season. There is a limit of three Equine Reproduction Laboratory/RME-leased recipient mares per client for the contracted dates.

Many breed registries require special embryo transfer enrollment on a yearly or lifetime basis. Mare owners should check with their breed association on specific rules related to embryo enrollment and registration of foals produced by embryo transfer.

On-site donor mare management

Mares are usually housed on site at the Equine Reproduction Laboratory to optimize reproductive management from the time the mare is bred through the date of embryo collection. Mares from the local area can go home for a few days and return for the embryo collection procedure or remain at the Equine Reproduction Laboratory until after the flush. Donor mares from a more distant location often remain at the Equine Reproduction Laboratory until a pregnancy is established in a recipient mare and confirmed at either day 16, 25, or 35 before returning home.

Equine Reproduction Laboratory-managed recipient mares must remain on site until day 35 of pregnancy. A privately-owned surrogate can go home the day of the transfer or may remain at the Equine Reproduction Laboratory until a pregnancy examination is performed.

Receiving shipped embryos

Shipment of embryos to the Equine Reproduction Laboratory for transfer allows the donor mare owner the flexibility to keep a mare at home and have reproductive management performed by their local veterinarian and still take advantage of the recipient herd managed at the Equine Reproduction Laboratory. We can also accept fresh or frozen ICSI-produced embryos for transfer.

An embryo transfer contract must be in place before the donor mare is bred and before informing our staff that the mare has ovulated. Your veterinarian must communicate with our staff on the day the donor mare ovulates, regardless of whether an Equine Reproduction Laboratory-managed recipient is to be used for transfer or if a privately owned mare is to be transported to the Equine Reproduction Laboratory as a recipient for transfer.

Recipient mares are synchronized based on communication from the referring veterinarian and the date of ovulation of donor mare. If a donor mare ovulates multiple follicles, an equal number of recipient mares must be synchronized as potential surrogates. Equine Reproduction Laboratory-managed recipient mares must remain on site until day 35 of pregnancy.

For ICSI-produced embryos, the ICSI laboratory should provide timely communication with the Equine Reproduction Laboratory so that recipient mares can be synchronized for transfer of shipped (non-frozen) ICSI embryos. An alternative is to have the ICSI laboratory freeze the embryo(s) for later transfer.

Outpatient (trailer-in) embryo recovery and transfer

For local and regional mare owners, breeding management can take place at home with your normal reproductive veterinarian. This service allows owners to have their mare bred and managed closer to home, but still take advantage of the technical skill provided by our veterinarians for embryo recovery and transfer. A recovered embryo can be transferred into either an Equine Reproduction Laboratory-managed recipient mare or a recipient mare provided by the donor mare owner.

An embryo transfer contract must be in place before the donor mare is bred and before informing our staff that the mare has ovulated. Your veterinarian must communicate with our staff on the day the donor mare ovulates, regardless of whether an Equine Reproduction Laboratory-managed recipient is to be used for transfer or if a privately owned mare is to be transported to the Equine Reproduction Laboratory as a recipient for transfer. An outpatient flush will be scheduled on day 8 post-ovulation whenever possible.

Recipient mares are synchronized based on communication from the referring veterinarian and the date of ovulation of donor mare. If a donor mare ovulates multiple follicles, an equal number of recipient mares must be synchronized as potential surrogates. Equine Reproduction Laboratory-managed recipient mares must remain on site until day 35 of pregnancy. A privately-owned surrogate can go home the day of the transfer or may remain at the Equine Reproduction Laboratory until a pregnancy examination is performed.

Transfer of embryos

Management and quality of recipient mares are key components of a successful embryo transfer. Ideally, recipient mares should be reasonably young (4 to 14 years of age) and reproductively healthy. Maiden mares are acceptable as are mares with a recent history of having successfully carried a foal to term.

All recipient mares managed at the Equine Reproduction Laboratory are evaluated for general medical health and reproductive health (ultrasound examination, uterine culture, uterine cytology, and possibly a uterine biopsy). The same screening process is recommended for owner-provided recipient mares.

Equine embryos are transferred non-surgically into the uterus of a synchronized recipient mare. A specialized embryo transfer instrument is used to transfer the embryo through the cervix and into the uterus. Recipient mares will be supplemented with progesterone or altrenogest (Regu-Mate®) following transfer. Progesterone supplementation is recommended for all recipient mares until 120 days of gestation.

Shipment of embryos to another transfer facility

If you have an embryo transfer contract with another recipient station, the staff at the Equine Reproduction Laboratory can breed the donor mare, flush the mare to recover an embryo, and ship the embryo to the other facility for subsequent transfer into a recipient mare. Our staff will communicate directly with the other transfer facility for synchronization of recipient mares and shipment of embryo(s). We prefer to ship embryos via commercial airline for same-day delivery (counter to counter) to a transfer facility. An overnight courier (i.e. FedEx) can be used as an alternative.

Embryo freezing

Equine embryos can be cryopreserved and stored in liquid nitrogen for later transfer. Normal in vivo produced embryos and in vitro produced ICSI embryos can be cryopreserved. A common cryopreservation technique is termed vitrification or ultra-rapid freezing. Small embryos (less than 300 µm in diameter) survive the freezing and thawing process well and yield acceptable pregnancy rates after transfer. Larger embryos are more challenging to cryopreserve and the pregnancy rate after transfer is often less than that of smaller embryos.

Advantages of embryo cryopreservation:

  • Embryos can be collected later in the summer or early fall, cryopreserved and transferred in the spring
  • Embryos can be collected and cryopreserved until a suitable recipient is available
  • Cryopreserved embryos can be stored indefinitely in liquid nitrogen