Good morning.... I have a lovely mare who in her day probably cost more than my house. I know own her at age 21, and she is still fantastic. She is a mare worth breeding, but alias, she is too old and I would not want to chance anything that might be ultimately detrimental to her (BTW, she was bred once and gave birth to two full sized and healthy twins .... both grew up and are doing fantastic).

I was curious of how difficult and how successful a process it would be to harvest her eggs and find a time to implant them in another mare next breeding season.

Do you have any idea what the success rate is, or even if a 21 year old mare's eggs are still viable.

Dianna,

Good Questions!

21 year old mares can still be fertile, with a couple of qualifications or issues.

1. The ova (eggs) of older mares (15 +) have been shown to have essentially degenerated with age. Consequently, they are associated with producing "defective" embryos. In some elaborate studies done almost 20 years ago, it was demonstrated the "aged" ova produced "aged" embryos that were not as viable as "young" ova. The embryos stay in the oviducts instead of being released into the uterus at the normal time. This results in decreased embryo recovery rates in older mares compared to the younger mare. Expect to have to breed and flush your mare on more cylces to recover a viable embryo.

2. The second part of your questions is in regard to harvesting and freezing "eggs" this year for transfer next year. The mare ova (egg)has some "unique" characteristics that have so far, prevented us from freezing them successfully. We are however, able to freeze early (Day 6) embryos.

The process is similar to the regular embryo recovery for direct transfer, except we flush the donor mare on Day 6 post ovulation to recover an earlier stage (morula) embryo that withstands the freezing process. After recovery, the embryo is put through a series of equilibrations in solutions to protect it in the freezing process and then plunged into liquid nitrogen for storage.

As for the overall success rate of the procedure, you can expect to have to flush your mare on more cycles to recover an embryo (3-4) vs 1-2 for a younger mare and because you are trying to recover an earlier stage embryo (Day 6) the recovery rates are a little lower also. Once recovered the post thaw transfer rate is also lower than with a fresh embryo so to be sure you acheive a pregnancy I would suggest freezing 2.

My suggestion would be to forego the freeze and transfer fresh embryos this year.

Good Luck!

Thank you for taking the time to answer. I apologize for not getting back to the board sooner... life is so hectic.

I have been offered 2 mares to use to carry the embryo, and was wondering how long the mares would have to be kept together before we could expect them to cycle with one another..... I am hoping to accomplish this this year, even if it means a August or September baby in 2010 (here in AZ that shouldn't be a problem and as we are talking dressage not race, that also shouldn't be a problem.

Any pearls of wisdom?

Dianna,

In order to get your mares synchronized to cycle closely enough for embryo transfer, the mares are going to have to have their cycles regulated with hormones to come into heat together and more importantly ovulate within 24-48 hours of each other. The target is to have your donor mare, the one the embryo is flushed from, ovulate 24-48 before the recipient mare who the embryo is transfered into. I would suggest you find an experienced equine theriogenologist aka. reproductive specialist, who has experience with embryo transfer work. There is such an individual in Buckeye, AZ, Dr. Lloyd Kloppe at Durango Equine Veterinary Clinic. His clinic phone number is 623-386-2928.

Good Luck!

Thank you. I have actually already spoken with Dr. Kloppy, except he will only send the embryos out and that doesn't work for me. There is another local vet well versed in this and I have worked with him for many years.

This is exciting, isn't it!