Repro2- Mare Hormone Therapy and Breeding

  1. In what mares would you want to prevent/suppress estrus?
    performance animals that are competing
  2. How long is estrus in a mare? How long after estrus does she ovulate?
    • estrus: 4-9 days [LONG]
    • ovulation: 24hrs after estrus
  3. As far as PGF injections, ___________ has reduced side-effects as compared to ___________.
    Estrumate (Cloprostenol); Lutalyse (Dinoprost)
  4. Give PGF injection to a _______ CL; estrus will occur in ________, and ovulation will occur in _________.
    >5day; 3-5 days; 7-10 days (24hrs after estrus)
  5. Reasons for variation (of days to respond) in responses to PGF injection?
    depends on stage of follicular wave (how big was her follicle when you gave the injection?!)
  6. How do you short cycle a mare?
    give PGF injection during diestrus
  7. When is natural PGF released during a mare's cycle?
    day 14 (same as cow)
  8. How can you induce luteolysis of a refractory CL (less than 5 days old)?
    give lutalyse twice a day for three straight days
  9. What drug can you use (preferred ecbolic drug post-ovulation) post-breeding to clear fluid from the uterus?
    oxytocin (DON'T USE PGF-WILL AFFECT FERTILITY- delays progesterone production from Cl)
  10. If oxytocin is given before day 10 of the cycle,...
    it disrupts luteolysis and prolongs CL function--> retained CL (used in performance horses to prevent cyclicity)
  11. What requirements must be met before you induce ovulation in a mare?
    • uterine edema
    • relaxed cervix and uterus
    • pre-ovulatory follicle (>35mm)
  12. Why must a mare be in heat before you induce ovulation?
    follicle must be pre-ovulatory (>35mm) because it needs LH receptors to be affected by the LH surge and ovulate
  13. What drugs can you use to induce ovulation in a mare?
    GnRH- Deslorelin, Sucromate (only FDA approved drug), hCG
  14. Once you give ________, the mare should be induced to ovulate within ________.
    GnRH; 40-48hrs
  15. What are the issues with the GnRH Ovuplant implant (not available in the US btw)? (2)
    down-regulation of pituitary, delayed return to estrus due to low FSH [ which is why you should remove the implant after ovulation]
  16. What should be the strategy to induce ovulation in old mares or mares late in the season?
    GnRH and hCG (4hrs after GnRH) together
  17. What are uses for progestogens in mares? (4)
    extend luteal phase, maintain a pregnancy, suppress estrus, synchronization
  18. What drugs are progestogens used in mares? (3)
    ReguMate, Altenogest, injectable progesterone
  19. Estrus occurs _________ after withdrawal of ReguMate.
    3-5 days
  20. What is the gold standard method for estrus synchronization in mares?
    progesterone + estradiol for 10-14 days--> estrus 3-5 days after that's done--> hCG and ovulation 8-10 days after that--> breed
  21. The average estrus cycle in a mare?
    21 days
  22. How long is the follicular phase in a mare's cycle?
    4-7 days
  23. How long is the luteal phase in a mare's cycle?
    14-15 days
  24. Why would we want to manipulate a mare's photoperiod?
    to induce estrus early because the birthday for foals is January 1st (need to be bred by February; don't usually enter cyclicity until spring)
  25. How do you manipulate the photoperiod?
    100W bulb in a 12x12' stall for 16hr of light a day, starting 2 months before breeding (start Dec. 1)
  26. What is the result of manipulating the photoperiod?
    mare goes through the transition period early and has large follicles but no ovulation--> then starts cycling
  27. When is the optimal time to breed a mare during her cycle?
    as close to ovulation as possible
  28. What is the least fertile type of semen?
  29. Sperm selection takes place at the ___________.
    uterotubule junction (UTJ)
  30. How long after breeding should you lavage the uterus without decreasing fertility?
    4hrs post-insemination (remove fluid/bacteria; there are already sufficient sperm in the oviduct)
  31. What is the lifespan of an oocyte after ovulation?
  32. How long do fresh, cooled, and frozen semen live in a mare, respectively?
    • Fresh- 48hr
    • Cooled-48hr
    • Frozen- 12hr
  33. What are the advantages of AI? (6)
    efficient, increase number of mares bred, allows semen transportation, minimize transmission of disease from stallions, eliminates transmission of disease from mares, reduces risk of injury
  34. Disadvantages to AI? (3)
    requires training, cost, increased risk of injury to semen collector
  35. Minimum number of sperm in fresh semen?
    500 million
  36. Minimum number of sperm in cooled semen?
    1 billion
  37. When should you order semen to breed a mare?
    when in estrus and has a follicle >30-35mm
  38. What medication should you give when you inseminate a mare with a 30-35mm follicle?
    hCG or GnRH at breeding; come back and check for ovulation in 24hr
  39. What protocol should you abide by when using frozen semen for insemination? (3)
    exam for ovulation every 6-8hr, AI within 12 hrs of ovulation, use hCG or GnRH to induce ovulation
  40. Describe the timeline of estrus manipulation and breeding with frozen semen.
    [edema and pro-ov follicle] 6am, hCG--> 24hr+ US [no ov]--> 30hr+ US [no ov]--> 36hr+ US [ov--> AI]
  41. What can you do post-breeding to minimize risk of infection and fluid accumulation? (3)
    oxytocin, uterine lavage, antibiotic (in necessary)
  42. Normal mares should clear any fluid from the uterus within ________ of breeding without any drugs/lavage.
  43. What are the current technologies in assisted reproduction in mares? (4)
    embryo transfer, oocyte transfer, intracytoplasmic sperm injection (ICSI), cloning
  44. What are indications for embryo transfer? (4)
    valuable older mares, increase production from superior mares, physically unsound mares, performance mares (still performing but want foals)
  45. What is imperative for embryo transfer to be successful?
    recipient mare and donor mare MUST be synchronized
  46. Do you need to place the embryo in a specific place when performing ET in a mare?
    NO (unlike cows) luetolysis is a SYSTEMIC process; also, the embryo is going to move around the lumen of the uterus anyway
  47. What is the only way to tell a clone from the original animal?
    mitochondrial DNA
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Repro2- Mare Hormone Therapy and Breeding
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