Embryo Transfer

Embryo Transfer


Collection



Basic Information image



Synonym(s)


Embryo transplantation



Overview and Goal(s)




• Embryo transfer (ET) consists of transferring an embryo collected from a donor mare to a recipient mare (Box 1).


• Commercial ET programs include multiple steps leading to the transfer of the embryo: Donor and recipient selection and synchronization, donor insemination, recovery, and transfer of the embryo.


• The major limiting factor in most equine embryo transfer programs is recipient management. Veterinary practitioners may provide a donor management and embryo collection service and ship cooled embryos to an embryo recipient facility (within 24 hours).



BOX 1 Characteristics of Equine Embryos


The embryo travels from the oviduct to the uterus about 6.0 to 6.5 days after ovulation. At day 6 (morula stage), the embryo is about 200 µm (range, 130–750 µm) in diameter. At day 7 (young blastocyst stage), the mean diameter is approximately 400 µm (range, 130–1400 µm), and at day 8 (blastocyst stage), the embryo is about 1100 µm (120–3900 µm) in diameter. For embryos that are 300 to 2000 µm in diameter, the pregnancy rate reaches 50% to 60%, with an expected 10% embryonic loss. Embryo loss rises to 20% for embryos smaller than 300 µm or larger than 2000 µm in diameter. Embryos bigger than 2000 µm are also more fragile and require adequate handling to obtain comparable pregnancy rates. The recovered embryos can be transferred fresh, cooled, or cryopreserved. Embryos larger than 300 µm in diameter do not tolerate cryopreservation well, but survive better in cooled storage.



Indications




• Multiple foals from individual genetically superior mares are desired in a short period of time


• Mares in competition


• Subfertile mares (unable to maintain a pregnancy to term)



Contraindications




• Infertile donor or recipient mares in which cervix, uterine, oviductal, or ovarian disorders have been identified.


• Some breeds do not register foals born from ET (eg, Thoroughbreds).


• Most breeds limit the number of foals registered per year per mare.



Equipment, Anesthesia




• Sedation: Acepromazine is preferred because there is less occurrence of pneumovagina complicating uterine manipulations.


• Collection equipment and supplies:


image Several types of Foley catheters are available; choice is generally based on individual experience and preference.

image Different sizes of bores and balloons are available; choice is dictated by breed and size of the mare.

image Two types of catheters may be used: two-way or three-way. Most practitioners use a two-way catheter with a Y-junction.

image Prewarmed collection media: Ready-made commercial embryo flushing media are available. Some are complete and ready for use; others may need addition of fetal calf serum (at least 3 L). Alternatively, Ringer’s lactate may be used.
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Jul 24, 2016 | Posted by in SMALL ANIMAL | Comments Off on Embryo Transfer

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