Before I talk about Dominant White, it might be helpful to pull one of the archived posts from my studio blog. I still need to finish pulling the posts that deal with horse color over here to the Tapestry blog, but since this one is relevant I’ll repost it now.

(Previously posted on August 30, 2007)

Exciting News in the World of Horse Color

One of the downsides to publishing your theories is that you stand the chance of later being proven wrong. Or at least missing the mark by a bit.

Ten years ago I wrote an article entitled A Study of White Horses – Not What They Seem, where I questioned the existence of Dominant White in horses. My skepticism was based on my own research into the backgrounds of as many white-born horses as I could find. From that I came to believe that most of the horses designated as Dominant White were more likely to be extremely marked sabinos. I failed to find horses that fit the profile for Dominant White, so I began to suspect that the color did not exist – or perhaps no longer existed since there were anecdotal stories of horses that had fit the profile in times past.

It appears that my speculation was wrong, at least in terms of whether or not there was such a gene in horses. Not only are there real, live Dominant Whites, but the Swiss team that identified them has been able to test for it. So eventually we will know for sure which horses carry the gene. (It is thought that the gene is extremely rare, so it is likely that many of the white-born horses are still just sabinos.)

Other things are in the works, too. A Swedish team found the mutation for grey, though a test is not yet available. UC Davis has been working on dun, and of course there is the ongoing research on the appaloosa patterns. Pretty soon there won’t be anything left to guess about when it comes to horse colors!

That blog post was made in 2007. The article I wrote ended this way:

Given the breeding records of the aforementioned “white” horses, I have come to wonder if Dominant White really does exist. But it is clear that even if it does, the majority of white-born horses are probably sabino whites.

Much of the research for the original article was done between 1992 and 1995, when I had access to the archives at the Tennessee Walking Horse Breeders’ and Exhibitors’ Association. Looking through old show catalogs and registry records, I found a lot of horses that looked like the horse above, Silver Sultan. (Photo from the TWHBEA archives)  Even more were recorded in the early stud books.

(Don’t worry – the highlighting was done on the image, not the book itself! The only way I mark my books is with post-it-notes, which are visible there on the pages behind this one. Those all mark sabino-patterned or white horses that are recorded as having blue eyes so that I can enter them in my notes. There aren’t any post-its closer to this page because those have already been entered. I am perpetually behind with formal records like these.)

I had a complete set of Walking Horse stud books, which were a gold mine of information because breeders submitted (and the registry printed) detailed color descriptions. Because I was interested in how sabino might work, I developed an elaborate numerical system for evaluating just how much white the horse had, and then set about assessing how horses with different amounts of white produced when crossed with mates with differing amounts of white. In hindsight, it was probably far less useful than the time spent justified! But the one take-away was that the white horses all had two sabino parents, and in almost all cases the numerical value of the parents was pretty high.

The way I scored the horses actually skewed this, because I grew up in the Tennessee Valley and I knew that many horsemen called a horse with indistinct body spotting “roan”. Taking that into account, if the horse had enough points based on markings – if I could be pretty sure it was not a dark-headed roan – then it got extra points if roan was used in the description. Many of the horses probably didn’t have body spots, or at least weren’t as patterned as their number value would suggest, but I was weighing a trait that was tied to the white even if I didn’t know it at the time. That is because the gene that causes sabino-white, Sabino1, tends to produce really roany horses, even when they are not very spotted. This old-fashioned Walking Horse mare is a good example.

Finding that link between white-born horses and sabino in both parents was why I wrote the article. Still, there were horses that did not fit my theory. In the article I speculated that in some breeds sabino might be linked in some way to the chestnut gene. There was no apparent link in the Walking Horses, which inherited spotting without any real difference related to base color that I could tell. I did know, though, that in some breeds (like Arabians) there was a noticeable difference in the amount of white a chestnut horse might inherit compared to a bay or black horse. I wondered at the time if this might play a role in the white-born horses that had parents with low numerical values (ie., little to no white), since in most of those cases the parents were bay or brown.

The biggest limitation was that most of the white-born horses I could find were long gone, and in many cases only partial records remained. I published what I had, and hoped that the article might flush out a bit more information. If your heart is truly in research, you really do want those corrections, because where you are wrong is where you learn.

My correction didn’t come for another ten years, but it did come. Almost all the horses that didn’t fit my theory quite exactly right were found to be Dominant White. R Khasper. White Beauty. Puchilingui.  Those that weren’t in the study fit the pattern for being Dominant White.

Tomorrow I will post pictures of Sato, the palomino Dominant White Thoroughbred stallion from one of those identified families. I was fortunate enough to see him in person in Kentucky, and talk to his owner, April Wayenberg. He is particularly interesting because he is more colored than a lot of Dominant Whites. He is also extremely photogenic, so I took hundreds of photos.

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