Management Of Mares For Chilled Semen

Chilled semen can be a highly efficient means of getting your mare pregnant saving on transport, agistment and gaining the opportunity to use interstate and over international stallions.

The keys to success are:

§         Fertile mares

§         Fertile semen

§         Accurate ovulation prediction

§         Reliable semen transport

There are a number of ovulation synchronisation methods.  The following is the simplest and most commonly used and works in most cases at GVH.  Other methods may be prescribed particularly early in the breeding season or when a more precise synchronisation of ovulation is required

1)     Determine suitability for AI program. Perform a full reproductive examination including an ultrasound. If any abnormalities including cysts or fluid accumulation are detected, the uterus is swabbed and perhaps biopsied and is treated accordingly. This is best done early in the season to allow adequate time to treat the mare.

2)     Prostaglandin the mare on Wednesday evening and Thursday morning to bring the mare into season. Note: approximately 25% of mares may not respond to this injection. If they have been in season over the past 5 days they generally will not respond and repeat injection will be required.

3)     Notify the stallion's owner that the mare has been given a prostaglandin injection and a semen collection may be required early the following week.

4)     The mare is delivered to GVH Sunday/ early Monday.

5)     Reproductive examination is performed to assess follicle development. Mares will generally ovulate on the Tuesday, Wednesday, and Thursday of that week.

6)     Order semen when we have a 35mm follicle and administer H.C.G or Ovuplant if assistance with ovulation is deemed necessary. (Note: H.C.G generally assures ovulation 35hrs post injection or Ovuplant at 40hrs post injection)

7)     Ultrasound the mare the next morning to check for follicle status.

8)     The mare is inseminated immediately on arrival of the semen. Sperm will live longer in the reproductive tract than in the refrigerator.

9)     The mare is examined at 24hrs-post insemination to check for ovulation and fluid accumulation in the uterus. If the mare failed to ovulate or if ovulation is not pending, further semen is ordered. If fluid is accumulating in the uterus, a uterine lavage is performed.

10) Pregnancy test mare 12 to 14 days later.

Management Of Mares For Frozen Semen

Insemination of mares with frozen requires special consideration because of the generally short life of frozen sperm once it is thawed. This requires great precision with the synchronisation of insemination and ovulation.

The goal is to inseminate within 12 hours prior to or 6hrs after ovulation. This ensures that viable sperm are in the oviduct for any mare that ovulates in the 12 to 48 hour window, following the administration of H.C.G or Ovuplant on 35-40mm follicle.

If multiple doses of semen are available;

a)     Continue to examine the mare twice daily and inseminate 24hrs after H.C.G or 30 hours after Ovuplant.

b)     Examine the mare 18 hours later and re-inseminate even if ovulation has occurred.

c)     Examine the mare the next day (24hrs later) to ensure ovulation. Re-inseminate if a follicle is still present.

If a single dose if semen is available;

a)     Examine the mare every 6hrs from 24hrs post Ovuplant or H.C.G.

b)     Inseminate on the detection of ovulation.

Do the post ovulation ultrasound 24hrs later (as with chilled semen) and lavage uterus if necessary.

Embryo Transfer Program

Embryo Transfer (E.T) is a technique where 5 to 8 day old fertilised embryo's are collected from one mare (a donor) and transferred to another mare (recipient).

Embryo transfers were first conducted in horses in the early 1970's but has only gained widespread acceptance by breed societies in recent years, resulting in a surge of interest among breeders.

ADVANTAGES:

§         Multiple pregnancies from the mare each season. 6 is a reasonable expectation.

§         Pregnancies from older mares or mares that are unable to carry a pregnancy to term.

§         Pregnancies from young performing mares.

§         Multiple pregnancies from a single mare by different sires.

DISADVANTAGES:

§         Lack of a super ovulation technique. E.T in mares utilises their natural cycle. Note: E.T has no effect on the subsequent fertility of mares.

§         A considerable amount of expertise is required to conduct successful E.T programs.

§         Expense.

§         Use of frozen semen can limit the success of E.T programs.

DONORS:

§         Superior genetics.

§         Young and fertile or proven brood mares.

§         Older mares with a poor-breeding history result in embryo's being recovered in 20% of flushes.

§         The mare is inseminated as usual.

§         Embryos are collected 7 days after ovulation.

§         The flushing technique has very little effect on the physiology of the mare and she can be programmed for another E.T program on the day of collection.

§         Mares remain in work whilst being flushed.

§         Mares can be flushed each fortnight.

§         Best results are obtained when the stallion, donor and recipient are all at the E.T centre.

RECIPIENTS:

§         Must be fertile mares with no history of reproductive problems.

     We prefer mares that have had a foal, but we regularly use maiden mares preferably           quiet tractable mares.