I do not know any science but would think the horse has to have the genes from its parents but perhaps the womb environment would affect what genes are expressed? (But of course my knowledge of environment affecting gene expression is limited to one hour of PBS NOVA!)
“I” don’t think being an ET horse lowers quality at all. I have first hand experience with one so my opinion is based from experience.
HOWEVER, I do wonder how/if the uterine environment affects markings. My mare is rabicano roan but both of her bio parents are solid with no white (sire) and very minimal white (dam-tiny star) markings and at least her sire does not pass white to the offspring. Her receipant dam was a blue roan. Every year my mare gets more and more roan/white hair all over her body.
My mare’s DNA test show she is 100% from bio parents. Nothing about how she looks in type and movement look like the receipant mare (a qh type) - at all. The quality is definitely from the parents.
So, I would not worry about ET and poor quality. I would just use a receipant mare with lots of chrome if you wanted chrome. 
Remember the cloned kitten? The kittens markings were different than it’s clone even though they had identical DNA. So when it comes to markings, DNA doesnt appear to be the only factor as the article says: http://news.nationalgeographic.com/news/2002/02/0214_021402copycat.html. “” She is not, however, identical to her DNA donor. The reason for this is that the pattern on cats’ coats is only partly genetically determined—it also depends on other factors during development.""
What’s amusing to me, I was joking when my mare was a baby about how I wished some if her recp dam’s roaning would rub off on the filly. Little did I know…it would. Now to be fair, it could just be a huge coinicidence.
