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1. Embryo Transfer in Horses
2. History Embryo transfer was initially performed in 1890 by Walter Heape of Cambridge where a Belgian hare doe fostered the fetal development, of another variety of rabbit (an Angora).
3. History In 1974, Japanese researchers Oguri and Tsutsumi first to perform non surgical ET between mares.
Gradual adaptations of these original procedures have developed into a variety of modern practices.
4. Why Perform Embryo Transfer Prevent interruption of show career
Obtain more than one offspring from a mare each year
Obtain foals from mares with low biopsy scores
Marketing of embryos
5. Embryo Transfer Identification of a suitable donor
Recipient selection
Donor / Recipient Synchronization
Embryo collection and handling
Transfer procedure
Surgical
Non- surgical
6. Advantages, uses Obtain foals from older or otherwise subfertile mares who are unable to maintain pregnancy
Obtain foals from mares without taking them from competition.
Obtain more foals from superior mares
Obtain foals from very young, cycling mares
Improve productivity of fertile mares with lesser genetic potential
7. Disadvantages, limitations Place health of embryos at risk
Expensive
Typically single embryo/collection
Subfertile donor mares are generally less productive
Aged mares produce fewer embryos, of which, many are lesser quality/survivability.
Superovulation difficult
8. Superovulation Foltropin, E-FSH analog (Bioniche)
2x Daily injections of 12.5 mg beginning before appearance of a dominant follicle
day 6-9 after ovulation (PGF on day 6)
Give HCG when majority of follicles >35mm
Increase recovery from .5 embryos/collection to 1.9 embryos/collection
Cost = $400 to $500 / mare
9. Efficiency Rate = % pregnancies per donor ovulation Recovery rate 50 to 70%
Success rate also 50 to 70%
Low efficiency = 25% pregnancies from donor ovulations
High efficiency = 50% pregnancies from donor ovulations
10. Factors that influence success Donor selection
Recipient selection
Donor preparation
Synchrony of recipient
Recipient preparation
Recovery procedure
Embryo preparation
Method of transfer
Management of recipient
11. Donor Selection Superior marketability
Healthy
Ages 2 to 15 ideal
Clean culture
Easy to handle
Estrous cycle characteristics
Natural production of follicles early in year
Normal cyclic characteristics
12. Recipient Selection Similar in size or larger
than donor (esp. pelvic size)
Age 3-10 ideal
Sound reproductive history
Normal reproductive tract
Normal cycle characteristics
Normal physiology
Normal teasing behavior
Good maternal characteristics
13. Scheme for Equine Embryo Transfer Synchronize ovulation between donor and recipient mares
Breed Donor mare- day of ovulation = Day 0
Flush uterus on day 7
Wash embryo and load into transfer instrument
Place embryo in uterus of recipient mare
14. Synchronization between donor and recipient
15. Donor - Recipient Synchrony Ovulation of recipient should occur between 1 day before to two days after the donor
16. Estrus Synchronization
17. Regumate
18. P & E (most effective)
19. Superovulation Foltropin, E-FSH analog (Bioniche)
2x Daily injections of 12.5 mg beginning before appearance of a dominant follicle
(day 5 – 8 after ovulation)
Give HCG until majority of follicles >35mm
Increase recovery from .5 embryos/collection to 1.9 embryos/collection
Cost = $400 to $500 / mare
20. Donor preparation Day 7 after ovulation
Tranquilize
Rectal suppressant
Rectal evacuation
Perineal cleansing
21. Embryo Collection Procedure
22. Flushing Filter for Searching
23. Embryos recovered
24. Embryo Preparation Searching and handling embryos
Sterile disposables
Specially formulated holding media
Above room temperature
Wash 4x in 200x vol
Control air flow over dish
Load for transfer
25. Embryo Handling
26. Transfer Method Surgical
Non-surgical
Vaginal cervical access after digital dilation/uterine access per rectum
Vaginal cervical access/careful insertion through internal os without digital dilation
Cervical access using speculum, uterine access using forceps to retract cervix
27. Surgical ET Preparation
28. Non-Surgical ET Instruments
29. Non-Surgical ET Instruments
30. Recipient preparation Banamine
Dormosedan
Empty rectum
Cleanse perineum
31. Recipient Management Re-examine 5d after transfer
Search for ~1cm vessicle
Re-examine ~20 d after transfer for heartbeat
Expected foaling date is ~11 months after transfer date
32. Embryo Transport Similar to cooled semen transport
Media instead of extenter
Embryo placed in a tube instead of syringe or bag
Cooled in equitainer
Attempt 24hr viability
33. Embryo Cryopreservation Only efficient in embryos that are <200um in diameter.
Morulas (day 5)
Very early blastocysts (day 6)
Not …
Mature blastocysts (day 7) > 400um
Expanded blastocysts (day 8) > 800um
34. Factors that influence success Donor selection
Recipient selection
Donor preparation
Synchrony of recipient
Recipient preparation
Recovery procedure
Embryo preparation
Method of transfer
Management of recipient