embryo transfer in horses

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embryo transfer in horses

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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

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