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Embryo Transfer

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Embryo Transfer

Equine embryo transfer has been around the United States for 25 plus years, but only in the past 5 years has embryo transfer gained in popularity.  The reason for the sudden increase is the now allowed multiple registry presently by AQHA, APHA, ApHC (Arabian) and warmblood associations, increased percentage of conception by embryo transfer, easier form of implantation, and increase in availability of embryo transfer, as well as, decrease in cost.

Five major reasons exist for the use of embryo transfer in your breeding program today:

A.  To obtain a foal from a mare with uterine disease or injury that will not allow her to attain and carry a pregnancy to term.

B.  To obtain a foal from a mare with cervical scarring/tearing or other injury that will not allow her to attain and carry a pregnancy to term.

C.  To obtain a foal from a mare that is currently competing in events so that her reproductive history can begin at an earlier age.

D.  To obtain a foal from a mare with proven bloodlines or show record and eliminating the possibility of injury during foaling.

E.  To obtain a foal from a mare that may be too small to attain and/or safely carry a pregnancy to term.

The actual procedure of flushing and implanting an equine embryo is actually not a difficult process, but the success of this process is solely dependent upon the successful completion of the steps prior to this.  Eight (8) steps exist to complete a successful equine embryo transfer.

1.)  Preparation of the donor mare with a breeding soundness exam, including ultrasound evaluation, uterine culture and sensitivity with appropriate treatment of the uterus when necessary, and evaluation of semem accessibility.  Any surgical procedures such as urine pooling correction or perineal reconstruction, and caslicks procedures should be performed will prior to breeding season.

2.)  Evaluation of recipient mare availability.  The greatest success of embryo transfer conception will arise when using a large band of recipient mares that are available for commercial use.  If you are attempting to use only one or two recipient mares per donor/embryo, then through evaluation of each recipient mare candidate must be implemented.  An evaluation of the recipient mares equal to that of the donor mare must be performed.  Uterine, ovarian, and cervical abnormalities and those greater than 10 years of age need to be struck from the list of possible candidates for recipient mare use.

3.)  Timing of the recipient mare to ovulate one to two days after the donor mare.  If you are using a commercial recipient herd, then a phone call to the operation the first day of breeding and the day of ovulation should be sufficient to allow proper timing of a recipient mare.  If you are attempting to use one or two recipients by mare, then the use of certain hormones including regumate, prostaglandin, and HCG will be necessary to synchronize both the donor and recipient mares cycles and ovulations.  The use of the medications along with frequent palpations to determine when and how to use them properly is sometimes a difficult task, but has been successful in many situations.

4.)  Proper timing of insemination of the donor mare with good quality viable semen.  An embryo can not be retrieved from a mare that is not pregnant.  Breeding the donor mare through live cover or artificial insemination with cooled semen is acceptable.  The use of frozen semen will yield a lower conception and embryo recovery rate.  Determination of the actual day of ovulation of the donor is necessary to perform the embryo collection on Day 7 post ovulation.  Performing the collection 2 days prior and 2 days later than the 7 day time will yield no embryo recovered or recovery of an embryo to large or unacceptable to implant in the recipient mare.  The day of ovulation of the donor mare is very important to determine.  

5.)  The embryo collection is performed on Day 7 post ovulation of the donor mare.  The mare is sedated to control the discomfort of the flush.  The vulva and perineum area is surgically prepared (cleaned/sterile/tail wrapped) to prevent contamination during the embryo collection.  A sterile catheter is placed trough the cervix with "Y" tubing attached to bags of fluids.  The fluid is a modified saline solution with additives to promote embryo viability.  The uterus is distended with this fluid and massaged to facilitate movement of the embryo.  Then, the fluid is drained through a cup with a filter to catch the embryo in a small amount of fluid.  At this time, the embryo is too small to be seen by the naked eye.

6.)  Identification of the embryo.  The small size of the embryo requires identification with the aid of a microscope.  The cup of fluid is gently poured into a grid search dish and searched through.  When an embryo is found, it must be retrieved by a micro-pipette, placed in clean fluid and prepared for implantation into the recipient mare.

7.)  Implantation into the recipient mare.  The recipient mare is sedated to control movement.  The
vulva and perineum area is surgically prepared (cleaned/sterile/tail wrapped) to prevent contamination during the embryo implantation.  Implantation of the embryo into the recipient mare through the vagina and cervix is performed in an expeditious and precise manner for the highest conception rates.  If done improperly, contamination of the uterus from the placement through the vaginal vault is the biggest risk of the vaginal placement of the embryo into the recipient mares uterus.

8.)  Post Implantation Care.  The recipient mare receives Regumate daily for the maintenance of pregnancy.  Progesterone supplementation either by use of Regumate orally or Progesterone injections are recommended through the 10th month of pregnancy.

Each one of these steps must be successful for the completion of a successful embryo transfer with a resulting pregnancy and delivery of a live foal.  Our embryo recovery rate averages 80 to 90% and conception rates average 90% when we use the commercial recipient herd.  This percentage of pregnancy is reduced to 760% when we use a small number of recipient mares.

Equine embryo transfer can be a viable alternative to natural carry for many reasons.  Embryo recovery rates and subsequent pregnancy rates can be very high when the entire process of evaluation, breeding, embryo flushing, and implantations are all performed with diligence, care, and organization.


Embryo Pictures                                    First Miniature Horse Embryo Transfer

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Shenandoah Miniature Training and Foaling Center

Brandy or Carp Carpenter
24757 State Highway 56
Whitesboro, Texas 76273
(903) 564-9447
Fax: (903)564-7629


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