HGG Community Forums

You're probably getting an overlap of W1 and W1 or W1 and W3. W1/W1 is "very risky," while W1/W3 is "moderate risk." Even W1/TO can be taking a chance, though it is "low risk."

I reference the White Factor Risks chart from the FAQ a lot, because I can never remember off the top of my head which W has the potential to interact badly with which other kit markings.

Edit Ammit beat me to it. :) They also both have splash 2 (sw2) which is lethal if the baby gets a copy from each parent.

If I was going to GMT them for myself. I’d remove the mare’s W1, and SW2. Then I’d remove the stallion’s W1. I’m not a fan of W1, so there may be a different way to modify them.

I feel like we haven't talked about this in a little white on the forum, so I'm gonna include some resources and info you probably don't need, but may be handy for reference.

Here's the link to the White Factor risk chart!
https://www.huntandjump.com/faq.php#870

This only covers versions of the Kit gene, though.
So, to add, if one horse has any of the following, they cannot be bred to a horse with the same gene without risking a lethal amount of white!

-Frame
-Splash 2 (aka PAX3c70y)
-Splash 3 (probably irrelevant since it's very uncommon)

Because White Factor affects how likely a given combination of genes is to be lethal, when breeding a horse with a lethal white gene, it's probably best to choose a horse with less white overall, even if its genes are not dangerous themselves. White Factor is hereditary, but it has a pretty big random factor.

If you really want to breed those 2 individuals together, obviously you can if you're OK with the risk! Or you can GMT them, or of course simply breed them to different horses with less white.

The nice thing about that, is that not all their descendants will inherit the dangerous white mutations, so some of those descendants will be able to be bred together without the risk.