SB1 + W20 horses: Case study one

As many horse breeders would know, foals sometimes turn up looking completely different to what was expected. This Miniature horse foal is Yarreh Lane Flash Gentleman Jack. His dam (Yarreh Lane Morning Star) is black with a small star, and his sire (Southern Star Flashback) is bay with a wide blaze and two high socks. So why is this little guy mostly white?

We tested him for agouti, red/black, sabino 1, splashed white 1 and W20. The sire, Southern Star Flashback, has one copy of sabino 1. He turned out to be homozygous black (‘a a’ for agouti, ‘E E’ for red/black) with one copy of sabino 1 (from his sire) and one copy of W20 (from his dam). He doesn’t carry splashed white 1. This colt is mostly white because the combination of sabino 1 and W20 produces much, much more white than just W20 by itself, or just sabino 1 by itself!

If you are curious as to exactly why this happens, read more about W20, sabino 1 and the other W genes here.

On a side note, the owner asked me if W20 was common in Welsh ponies as the dam has a reasonable proportion of Welsh bloodlines. The answer is yes, it seems to be very common.

Thank-you Yarreh Lane Miniature Horse Stud (FB) for sharing this story and their photos.

Click here to test for Sabino 1 and/or W20

News Reporter