Embryo Transfer in Mares

In some cases, owners or practitioners performing embryo transfer choose not to have embryo recipients for a given donor mare. This avoids the hassles of purchasing, checking and maintaining recipients, as well as the expense and work involved with synchronization. In this case, the recovered embryo can be shipped to a referral facility that holds numerous recipients available for transfer at any given time. The drawbacks of this alternative are the risks involved with shipping an embryo and also that pregnancy rates may be slightly reduced when an embryo is not transferred immediately after collection.

For shipment, embryos are packaged into a sterile vial containing a commercialized medium, Hams F-10, that is buffered by diffusing it with a mixture of 90 percent nitrogen, 5 percent oxygen and 5 percent carbon dioxide. Prepared medium can be ordered from the transfer facility just prior to performing the embryo recovery procedure.

This medium is also supplemented with fetal calf serum and antibiotics.

Once collected and washed, the embryo is placed into a 3-ml sterile plastic vial containing equilibrated warm medium, and this is then placed inside a 50-ml medium containing centrifuge tube, as a precaution.

The 50-ml tube is packaged into an Equitainer for cooled shipment.

Packaged embryos should be shipped by airline or overnight courier service, and transferred as soon as they reach the transfer facility, optimally before 24 hr postrecovery.