This is an archived Horseadvice.com Discussion. The parent article and menus are available on the navigation menu below:
HorseAdvice.com » Equine Reproduction » Horse Breeding & Artificial Insemination » Twinning and Management of Twin Embryos »
  Discussion on Thoroughbred mare with twins-28 days
Author Message

Posted on Tuesday, Aug 31, 1999 - 1:12 pm:

My friend has a 8 year old thoroughbred mare who has settled with twins. She was ultrasounded again today (28) days and still is carrying two healthy babies- neither one is showing signs of poor health. The vet feels the twins are probably identical as they are so close to one another that he does not want to attempt to pinch one off. He gave the owner instructions to give the mare shots and abort both pregnancies. My friend wonders if she could/should wait until day 40 to see if one has died on its own or if she should have the vet attempt to pinch one off regardless of the risk to the other. Any suggestions? This mare has had two large foals for her owner in the past 3 years.

Thanks, Stace

Posted on Wednesday, Sep 1, 1999 - 7:41 am:

Hello Stace,
It is a little like gambling isn't it? If the two embryos are adjacent to each other and touching then there is a very good chance one will dissolve, but this has usually began by now.

She cannot afford to wait until day 40. The problem is that by about day 36 to 38 irreversible physiological events (formation of the endometrial cups) occur that will probably keep the mare from returning to heat for 3 months if aborted. But she can wait until day 34 post ovulation, this will give a little extra time for what should occur about 90% of the time. But don't delay later than day 34.

Interestingly there has never been a case of identical twons identified in horses, all that have been checked have been fraternal, and her twins indicate a double ovulation that implanted together: the most common outcome of twin vesicles.
DrO

Posted on Wednesday, Sep 1, 1999 - 7:26 pm:

Well you learn something new every day :-)

All the info I have studied on twins does not say that they cannot be Identical, but I will accept your info as other research I found had not bothered to test for it.

That brings up the next question, I assumed double ovulations occured one from each ovary. Under normal circustances is the ovulation on one side or both, how often would an ovulation occur from both ovaries. Is it more likely to occur in older mares.

In approx 11 weeks I can give you more info from my experience :-), The mare is now over 3 feet wide and has 76 days remaining, here's hoping everything is perfect :-)

Posted on Thursday, Sep 2, 1999 - 6:38 am:

I see double ovulations from the same and different ovaries, and have not noticed a pattern. Neither have I noticed a age relation. I am sure Ginter has studied both of these questions and I will see what he says. There does seem to be a breed correlation with both TB's and WB's having a greater incidence.
DrO

Posted on Saturday, Sep 4, 1999 - 1:04 pm:

Thanks for the response. Deb does not plan to rebreed this mare this year- so, she's not worried about the mare forming endometrial cups. She'd just like to give the pregnancy and nature its best opportunity to solve the problem. I've read studies which show that there is a "window" of time when one twin aborts without harming the other- and that the chances of double abortions increase as they age. But, how long could she let this continue before possible harm would occur for the mare? Must progesterone shots be given before a certain time period for the comfort of the mare?
This late abortion possibility stuff is actually making ME uncomfortable. (:

Thanks again,

Stace

Posted on Saturday, Sep 4, 1999 - 6:09 pm:

I think 60 days is the latest point where prostaglandin will cause abortions.
It does not seem to have an effect after this, as proved by the vet who owns the stallion my mare went to. She gave prostaglandin to one of her mares that was not cycling, she figured out later on that their own stallion had got to his daughter 2 months before, and she did not abort.

The problem seems to be that after 45 days I think it gets hard to detect twins as the uterous starts to DrOp below the pelvic bone.

Posted on Sunday, Sep 5, 1999 - 11:10 am:

Hello Everyone,
Darren is partially right. Between day 35 and 45 and onward it becomes more difficult to cause abortion with prostaglandins, but not impossible. I have seen the hypothesis that the eCG has a protective effect on the CL's preventing abortion but I have a simpler theory: Generally there are a multitude of CL's present of different ages, some are still immature and therefore resistant to the prostaglandin injection.

Usually abortion can occur if you give luteoluytic doses of prostaglandins (Lutalyse or Synchrocept) once daily for 5 days. This is fairly reliable but not fool proof: what if you have a ovulation the day you start or during the treatment period, you might miss this one.

Thorough ultrasound monitoring of reproductive events during and after is important. I have one literature reference that says this works up to day 120 but I draw the line at day 90.
DrO

Posted on Sunday, Sep 5, 1999 - 7:48 pm:

Thanks Dr.O

I will adjust my rule of thumb :-)

I did think it was strange that they didn't cause an abortion in their mare because it would have been less than 60 days. Once again I suppose it comes down to the mare :-).

Just another piece of information to file away in my head for future reference.

Posted on Monday, Sep 6, 1999 - 6:13 pm:

Thanks to both of you for your help- I will fill you in on the final outcome.
Stace

Posted on Wednesday, Sep 22, 1999 - 1:00 am:

Well, nature did not resolve this for the mare- She didn't lose either foal and they had to begin the abortion yesterday. She will be re-ultrasounded next week after treatment to make sure she is open again.

Both foals were growing well. Dang.

Thanks for the help-
Stace

Posted on Wednesday, Sep 22, 1999 - 7:58 am:

Bummer, thanks for reporting back. We have many who come and seek help here but do not have the courtesy to report back the final outcome which would be invaluable information for other members.
DrO
Home Page | Top of Page | Join Us!
Horseadvice.com is a BBB Accredited Business. Click for the BBB Business Review of this Horse Training in Stokesdale NC