Equine Embryo Transfer

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Equine Embryo Transfer

• By Ashley Culp

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What is Equine ET?

• Reproductive technology
• Collection of an embryo from a donor mare
• Transfer of embryo to recipient mare
• Recipient mare maintains the pregnancy and a foal
  is born 11 months later

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History

• 1890, the first embryo transfer was carried out
  in rabbits, England.
• 1974,the first successful non-surgical embryo
  transfer in horses was reported.
• Slow expansion due to resistance to
  superovulation and difficulty with embryo
  cryopreservation.
• 2002, AQHA approved the unlimited registration of
  foals from one mare during a given year using
  embryo transfer.
• Leading countries include US, Argentina, Brazil.

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Advantages

• Multiple foals from one mare
• Increased productivity in one breeding season
• Donor mare can stay in training
• Showing, rodeo, etc.
• Decreased risk of breeding injuries
• Produce foals from problem mares
• High success rates

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Recovery of the Embryo

• Collection should occur 7 days after ovulation
• Defined period for recovery
• Restrain the horse
• Wrap the tail, scrub area around perineum

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Embryo Recovery Steps of the Procedure

• Foley type catheter is passed through the vagina,
  cervix and into the uterus.
• The inflatable cuff of the catheter is inflated
  which allows for a tight fit against the cervix.
• Embryo flushing medium can be flushed into the
  uterus.
• Massage of the uterus, embryos become suspended
  in the flushing medium.
• Fluid is drained from the uterus into a small
  filter dish.

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Procedure (continued)

• 3 Embryo flushes should be performed
• PGF2a should be injected IM to remove residual
  fluid from the uterus
• Shorten cycle
• Help prevent endometritis
• Analysis of the embryos

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Embryo Recovery Pictures
Stocks to restrain the horse
Embryo flushing
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Recovery (continued)

• Use dissecting microscope to detect quality and
  developmental stage
• Grade 1-4 excellent to degenerate
• Late morula, early blastocyst, expanded
  blastocyst
• Embryo should be in the expanded blastocyst
  stage by
• day 7

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Ideal Donor Mare

• Older or injured mares unable to carry pregnancy
• Show mares competing in polo, rodeo, performance
  events, etc.

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Transfer of the Embryo

• Surgical
• Non-surgical

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Surgical Transfer

• Heavily sedate mare
• Flank laparotomy 4-6 inch flank incision
• Deposit embryo directly into uterus
• Higher pregnancy rates (75-90)
• BUT
• Impractical
• Increased cost, discomfort, anesthesia

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Non-surgical Transfer

• Transfer should occur within three hours after
  recovery.
• Tranquilization with xylazine or acepromazine
• Load embryo into insemination rod or embryo
  transfer gun
• Transcervical passage and deposit the embryo in
  the uterus

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Ideal Recipient Mares

• Young (3-12 yrs)
• Healthy, good cervical/uterine tone
• Excellent reproductive history
• Recipients should ovulate at a time similar to
  donor mare
• 1 day before or up to three days after
• Similar body size
• Thoroughbred embryos should not be transferred to
  recipient pony mares.

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Embryo Storage

• Immediate transfer
• Room temperature for 1-2 hrs
• Cooled, transported
• Store at 5 C, viable for 24 hrs
• Cryopreservation
• Not common due to difficulty
• Poor viability after thawing

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Cost

• Most companies have 5 different options
• EquiGen
• 1200 deposit
• 3000 to purchase pregnant recipient mare
• Additional costs
• EquiTransfer, Inc. estimates
• Send embryo, transfer 2400
• On site Embryo recovery, transfer 5000

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Cost-Effective?

• YES
• If the foal is worth 5000 or more as soon as it
  hits the ground.
• If the donor mare produces excellent offspring
  but cannot carry the pregnancy

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Cost-Effective?

• NO
• If donor mare is not extremely valuable
• If foal value does not cover costs of embryo
  transfer

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Animal Care/Welfare Concerns

• Surgical embryo transfer
• Complications
• Increased aftercare
• Discomfort
• Some countries have banned this
• Uterine infections
• Post-transfer

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Example Companies

• Embryogenex- Creekside Animal Clinic
• EquinGen, Equine Reproduction Center
• EquiTransfer,Inc.
• Dr. Carol
• Equine Embryos Inc.
• Equine Reproduction Concepts, LLC

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Conclusion

• Transfer of embryo from donor mare to healthy
  recipient mare
• Pregnancy rates of 70-85
• Cost-effective, safe, successful

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References

• Allen, WR (2005) The Development and Application
  of the Modern Reproductive Technologies to Horse
  Breeding. Reproduction in Domestic Animals
  (40)310-329
• www.creeksideanimalclinic.com/equine.html
• www.equigen.net/Embryo_Transfer.htm
• www.equineembryos.com/et-tech.htm
• www.equinereproduction.com/embryotransfer.htm
• www.equitransfer.com
• Hasler, John F. (2005) Embryo Transfer in Farm
  Animals. Encyclopedia of Animal Science

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References

• www.merckvetmanual.com/mvm/bc/182100.htm
• Squires, E.L. and E.M Carnevale and P.M. McCue
  and J.E. Bruemmer (2003) Embryo Technologies in
  the Horse. Theriogenology (59) 151-170
• Squires, E.L. and P.M. McCue and D. Vanderwall
  (1999) The Current Status of Equine Embryo
  Transfer. Theriogenology (51) 91-104
• Stout, T.A.E. (2006) Equine Embryo Transfer
  review of developing potential. Equine Veterinary
  Journal (38) 467-478
• www.vetmed.ucdavis.edu

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The End