Dominant White vs Sabino White

Other than a double-cream dilutes and grays, there are also two other patterns/mutations that have the potential to make a horse white colored. These alleles are dominant white and sabino white.

(Also, when I say "sabino", I am referring to the SB1 form of sabino.)

Sabino white is pretty basic - it's an almost-white horse that is homozygous for the sabino pattern.

Dominant white, on the other hand...well, there are eleven twenty different mutations found for it, and each mutation has a slightly different white pattern. As with the sabino nomenclature, each different mutation for DW is labeled with the number following (DW 1, DW 2, and so on).

The differences between how these two alleles look? Don't ask me. I still get it wrong.

What I can tell you, though, is that testing has been done on the DW allele and most horses with this dominant allele are at least 50% white.

Now, I haven't seen either a sabino white or dominant white horse face-to-face before, but I have a feeling the latter are less common since the DW allele's homozygous form is known as embryonic lethal and the foal is aborted before birth.

SB1 x SB1 = 50% heterozygous SB1, 25% homozygous (sabino white) SB1, 25% non-SB1
DW x DW = 50% heterozygous DW, 25% homozygous (lethal) DW, 25% non-DW
DW x non-DW = 50% heterozygous DW, 50% non-DW

Sabino white horse, image by Arsdelicatas on Wikimedia Commons.

Dominant white horse, image by Haase B, Brooks SA, Schlumbaum A, Azor PJ, Bailey E, et al.

Dominant white horse, image by Haase B, Brooks SA, Schlumbaum A, Azor PJ, Bailey E, et al.

Also, the Thorougbred farm Valley View Acres has quite a few pictures of their DW horses, and AnimalGenetic's article about the allele has information about the different genotypes linked to each mutation.