I know there is some variability, esp if the white is due to something like the sabino gene, but just curious. For example, if I have a mare with four high-ish socks, from a sire with four socks, with pedigree that includes a grandsire known for throwing lots of chrome, and she is bred to a stallion with four high socks and even some body white (non-stock horse), would the average resulting cross have socks?
Yes, the odds of pretty significant socks is pretty high here
The odds go up if the foal is red-based (chestnut, palomino, etc), as black extension (E, as opposed to red which is e) is known to suppress white expression.
When you have a black- or bay-based horse with lots of chrome, there are some boosters in play, and they tend to throw more white on their black/bay-based offspring.
Chestnuts with lots of chrome are less likely to produce bay/black-based foals with chrome
So it’s about the white color genetics the parents have, but also whether they’re black or bay-based (E?), or red-based (ee)
My observation has been that Frame Overo pinto expresses more on chestnuts than on black/bay, and that non pinto chestnuts also tend to have more socks and big blazes than black/bay.
But in Tobiano pinto there are a lot of black and white pintos with 50/50 balance of white and color.
ALL Overo white, which is non-Tobiano, non-appaloosa, expresses more on red-based colors. This covers splash, frame, white, sabino. And that’s without getting into the white-boosting patterns. Frame on its own doesn’t produce much white at all. All the loud Frame horse have some white boosting like W20 (which is very, very common), and then still, yes, more expression on red-based colors.
Tobiano is a color-linked gene. It’s gene is linked to extension. This doesn’t matter if the horse is EE or ee, or if he’s homozygous for Tobi.
But if a stallion is Ee, and hetero for Tobi, then To is linked to either E, or e. If it’s linked to E, then unless the mare also has To and it’s linked to e, then that stallion will never*** produce a red-based Tobiano foal, because his To always goes with E (which makes the horse black/bay/etc). Any red-based Tobiano offspring of those horses are from this example stallion passing e, and the mare passing e with Tobi linked. All his black/bay-based foals would be Tobi, and his red-based foals all solid, if the mare doesn’t carry Tobi.
*** there’s about a 7% chance the linkage will swap, so the E-To link stallion could produce a chestnut To foal, with a solid mare, if that breeding was in that 7% chance
Art Deco for example had the E-To link, so all (or at least the vast vast majority, I can’t remember if it was ever documented that he had a link swap) tobiano foals from non-To mares were black/bay-based.
But, if that Ee stallion’s To is linked to e, then you get a mix of black/bay-based and red-based tobiano offspring when bred to EE and Ee mares. Why? Because his e-To can be passed, and the foal can be either Ee or ee depending on what the mare passes, but with To. If he’s bred to ee solid mare mares, then all red-based foals will be tobi, and all Ee foals would be solid.
The % of white in Tobi is highly variable and not related to color
Thank you, totally interesting! I had no idea that Tobiano was color linked!