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Chimera and twinning

Equine-Reproduction.com Bulletin Board » Miscellaneous and Suggestions for a New Topic Category » Chimera and twinning « Previous Next »


Author Message
 

Diana Gilger
Senior Stallion or Mare
Username: Kdgilger

Post Number: 3595
Registered: 01-2008
Posted on Friday, August 27, 2010 - 01:19 am:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

OK, Jos...please help me settle something! LOL
If a mare has a chimera foal, does this mean that she is more likely to foal twins in future pregnancies?
Please and Thank You in Advance!
 

Jos
Board Administrator
Username: Admin

Post Number: 3004
Registered: 10-1999
Posted on Friday, August 27, 2010 - 10:37 am:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

As a chimera is formed from the combination of two fertilized oocytes, that is indicative that there must have been a double ovulation. As there is a tendency towards repeats of double ovulations in double-ovulating mares, yes, there is a possible tendency that in some cases she will be more likely to repeat.

However... (:-)):

It is important to bear in mind that twinning is nature's way of increasing the odds of establishing a pregnancy; the highest incidence of twinning is seen in barren mares, and the lowest in mares 60 days or fewer post-foaling. Nature is saying to itself "this barren mare can't get pregnant, so let's increase the odds, but this post-foaling mare is obviously fertile, so we don't need to worry about increasing the odds in her". Consequently, if we accept that there is a higher incidence of double ovulation in a barren mare, obviously, if she gets pregnant and has a foal, the following year she is no longer in the barren category, but has now joined the lowest percentage category of post-foaling mares. Hence, although there is a genetic connection in some mares with double ovulating mares tending towards production of double ovulating filly foals, and a continuously higher percentage of double ovulations themselves, there is also another category of double ovulating mares that is in a sense "environmental" in cause.

There are no straightforward answers in equine reproduction (at least when you ask me the question! :-))
 

Diana Gilger
Senior Stallion or Mare
Username: Kdgilger

Post Number: 3596
Registered: 01-2008
Posted on Friday, August 27, 2010 - 06:43 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

Jos, as usual, your answers are very helpful, and very much appreciated! You ROCK!
:-)
 

Holly
Senior Stallion or Mare
Username: Bonny

Post Number: 2222
Registered: 03-2008
Posted on Friday, August 27, 2010 - 07:37 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

OK Diana why did you ask??? Are we thinking twins with one of your girls? Yes I am nosey!!!
 

Diana Gilger
Senior Stallion or Mare
Username: Kdgilger

Post Number: 3598
Registered: 01-2008
Posted on Friday, August 27, 2010 - 08:42 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

I will catch you on your site tonight or call you, so as not to start unnecessary trouble here. LOL
 

Diana Gilger
Senior Stallion or Mare
Username: Kdgilger

Post Number: 3599
Registered: 01-2008
Posted on Sunday, August 29, 2010 - 02:00 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

JOS....what does it tell you if the mare was a 2 yr old maiden when she was bred?? Surely she doesn't fit into the "barren mare" category as a young maiden? Or maybe it's environmental? I just want to hear anything EXCEPT chances are this mare will twin again....LOL It's something that worries me alot with my minis, and she's one of my best bloodlines. ICK...now I'm pre worrying about next april !! hahaah! Does the foaling drama EVER end?
 

Jos
Board Administrator
Username: Admin

Post Number: 3005
Registered: 10-1999
Posted on Sunday, August 29, 2010 - 08:44 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

Mnffff.... Sorry, can't say what you want to hear! :-)

Why are you so concerned about twinning? Double ovulations increase your chance of establishing a pregnancy significantly. In one piece of research (Allen W.R. (2003). 29th Asian Racing Conference) it was shown that in single-ovulation mares 58% conceived, while double-ovulation mares had an 86% chance of conceiving overall, be that a singleton or twins. If this is coupled with a recorded 97% success rate in twin to singleton reduction it makes double ovulating mares more fertile at an 83% singleton pregnancy rate, and therefore more desirable in the broodmare band!

Which do you prefer? A 58% single cycle single conceptus pregnancy rate, or an 83% single cycle single conceptus rate?

Seems like a no-brainer to me.... :-)
 

Diana Gilger
Senior Stallion or Mare
Username: Kdgilger

Post Number: 3600
Registered: 01-2008
Posted on Sunday, August 29, 2010 - 08:57 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

Well, in this particular situation, I prefer that she ovulated just one! :-) The reason for that being that she has been bred back since June 12, and I *assume* it's already too late to 'pinch' one if it's a double...right? I guess If I'd known anything about this 'chimera' thing earlier on, I'd have willingly and safely had her scanned and I'd feel much better! LOL The good thing is, EMSA can xray the belly in minis, and we'll know if she's carrying twins in advance. If she does, they're pros at handling my horses...and she can go there to foal. I assume that if she is carrying 2, that I should from now on have her checked early on after breeding. What day post breeding do you recommend having them ultrasounded for this? I used to have all my mares ultrasounded at 16 days post breeding, but that went by the wayside when I figured out they're either bred or they're not..LOL Either way, I'll find out.
On a side note, did Equine Reproduction used to be further south on 35? Maybe near Marietta exit? I was coming back from Houston the other day, and saw an old sign with Equine Repro on it attached to a fence...but it was nowhere near Wynnewood.
 

Jos
Board Administrator
Username: Admin

Post Number: 3006
Registered: 10-1999
Posted on Monday, August 30, 2010 - 10:04 am:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

We recommend two pregnancy check ultrasounds per mare on all mares post-breeding - one before fixation at 16 days; the second before 28 days - as the minimum number.

Read the twinning article (follow that link).

On the other note... nope. Not us. We're 2¼ miles west of exit 64 off I-31 and haven't ever been located anywhere else in OK.
 

Diana Gilger
Senior Stallion or Mare
Username: Kdgilger

Post Number: 3605
Registered: 01-2008
Posted on Monday, August 30, 2010 - 12:33 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

Thanks for the info and the link to the article!!



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