Re: RC: Re: Breeding theories (was *Muscat)

[CMKSAGEHIL@aol.com]

In a message dated 9/10/99 9:33:31 AM Pacific Daylight Time, 
claudiaspears@hotmail.com writes:

<< All my resources tell me (vets, A&M,
 Colo. State Vet school and tech support) that an older mare has older eggs.
 They are with her since production started, so to speak. So how does this
 theory fit in?  >>

This doesn't really get to be a problem until the eggs are fairly aged.  
Long-term suspension in the division phase (which is where they are) will 
eventually lead to breakdown of bits of genetic material, which can lead to 
really oddball anomalies (if the fetus survives to be a foal) or to embryonic 
death, or just plain failure to settle.  One of the things that has made 
embryo transfer frustrating in these older mares is that one can harvest a 
completely wonderful-looking embryo and transplant it into a perfectly 
healthy recipient mare, only to have it resorbed at 35-40 days just as it 
does in its own mother.  After having this happen over and over, researchers 
began to feel that a great deal more fetal loss in older mares (20+) was due 
to flawed genetic material causing flawed embryos than they had previously 
thought.  Before, they had assumed that the fetal loss in these old mares was 
due to the aging of their reproductive tracts, making them unable to carry 
foals.

Heidi


=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
Ridecamp is a service of Endurance Net, http://www.endurance.net.    
Information, Policy, Disclaimer: http://www.endurance.net/RideCamp   
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=