I want to talk about the type of sabino that Criollo breeders call bragada, but before I get to that, it makes sense to discuss what I got wrong about sabinos in general. That’s because, in my early exploration of sabino, bragada was the part I missed. It is a pretty big piece of the puzzle, and not knowing where it fit meant I did not have a clear picture.
The flaws in “minimum” and “maximum”
White horses fascinated early geneticists, but they were not my original focus. I was interested in “crop-outs” – pintos that appeared unexpectedly in otherwise solid breeds. What I came to believe, based mainly on the Walking Horse studbook records, was that sabino was a pattern that existed on a continuum that started with horses like the one above and went on through to a horse that was entirely white. In this conceptualization, a horse with a blaze and stockings represented the “minimal” end of the pattern’s expression, and all-white represented the “maximum” expression.
In the early 1990s – just as the internet came along and made it possible to talk to other equestrians – this was considered a radical idea. More than one person pointed out the absurdity of my position with some version of, “What, are we supposed to think of horses with white markings as pintos? Where do you suggest we draw the line?” I had not thought of it that way, but when pressed, I had to admit that I did not know where to draw the line. What I knew was that certain types of white markings, body spots, and roaning appeared in related horses. The records also suggested that there was a dosage effect; the whitest horses tended to have two sabino parents.
My hypothesis of a continuum of expression worked reasonably well because my dataset came from a breed where (we now know) most sabinos carry Sabino-1. It fell short, however, when I was able to look at comprehensive records for a very different breed. In the late 1990s, the Arabian Horse Registry offered its pedigree database on CD-ROM. Where the old Walking Horse studbooks had written descriptions of markings, the more recent entries in the Arabian database had digitizing diagrams. It was a goldmine of information.
The white Arabians in my notes were the weakest links in my hypothesis. With Arabians, the “two sabino parents rule” that seemed so well-supported by the breeding records of hundreds of white Walking Horses only worked if sabino was defined very broadly. Perhaps more importantly, though, I could not connect the white Arabians with the Arabians that had more extensive white on their bodies. In Walking Horses, all the phenotypes on the continuum clustered into families; in Arabians, they did not.
Searching for the connection
Since I had more examples of crop-out pinto Arabians, I decided to focus on those. I knew that certain horses tended to get the credit (or blame) for producing “excessive white.” Fortunately for me, one of those horses was a popular sire whose stud career was recent enough that most of his foals had marking diagrams on file. That was Khemosabi.
Khemosabi had more than a thousand foals. Many of his sons were prolific sires in their own right. That gave me thousands of diagrams to analyze. At one point, the binders with marking diagrams of Khemosabi descendants took over one of the shelves in my library. The story they told was pretty clear. When it came to sabino patterning in Arabians, my hypothesis was wrong. If there was a continuum of white expression in sabino Arabians, it was one that did not stray far from the phenotype seen on the Paint Horse above or the one below.
In my notes at the time, I referred to this phenotype – blaze, socks or stockings, perhaps some white on the belly or girth area – as “flashy white sabino.” I did not know that it had a separate name in South America. However, the production records convinced me that while it shared some visual characteristics with the other sabinos, it was, in fact, a separate pattern.
With the bragada Arabians, I saw a different pattern of inheritance than with the sabino Tennessee Walking Horses. One of the most striking aspects of sabino in the Walking Horses was its wide range of expression. In the Arabians, sabino markings were inherited in a similarly dominant fashion, but with far less individual variation. The majority had what would be considered little more than extensive or “flashy” markings. Some had white on the belly or girth, but the amount of body white visible when the horse was in profile was limited.
Bragada was distinct from the other sabino patterns in that it tended to hover around the limit of what qualifies as a pinto, or in the case of breeds with “white line” rules, what disqualifies from being solid. Horses with more obvious body spotting did occur on rare occasions. Those usually had this phenotype. (I have used a photo of another Paint Horse because it was a particularly useful representative image.)
There were horses like this among the descendants of Khemosabi. What analyzing all those diagrams told me was that the horses in the body-spotted group were related to each other. They all traced back to the same Khemosabi son, but the other branches of his family all produced the expected bragada markings. The Khemosabi family gave me a large dataset that made it easy to see that the extensive patterns were separate. I checked this with the other cases I had, unrelated to Khemosabi, and I saw the same situation with each one. A horse would be born with a surprising level of white for his or her breeding, and they would then go on to pretty consistently produce it.
The Khemosabi son was eventually identified as carrying a new white spotting mutation (W15). Another horse I looked at, Fantasia Vu, was recognized as the founder of the W19 mutation. There are similar cases that have not yet been tested. I am pretty sure, based on what we now know, that they also have new sabino mutations.
The case for the name
In many breeds, white on the body can have a significant impact (good or bad) on the value of a foal. Because the amount (and location) of white is important, it is useful to refer to the less-extensively marked sabinos with a specific term. It also doesn’t hurt that the phenotype already has a name in a part of the world where it is common. It is even unique, short and easy to pronounce.
Using bragada for this type of patterning also highlights the fact that while sabinos (of all kinds) have a range of white expression, the width of that range can vary dramatically. Sabino-1 is notable for its wide range of phenotypes. Bragada patterns appear to have a more narrow one. (The W alleles that produce very white phenotypes also have a narrow range of expression.)
The idea that all sabino-type patterns have a broad range leads to mistaken ideas about where unexpected patterns originate. Invariably when a foal with extensive body spotting is born, comments will be made about this or that ancestor who was known to throw a lot of white. As the sabino Arabians show, those relatives with “a lot of white” and a suprisingly loud foal may have two genetically distinct patterns. Using the South American term for the more common “flashy-marking” phenotype helps to highlight that the more extensive patterns are unique to the families of their founders. Those wanting obvious pintos would be better served using members of the founder’s family, rather than going back to a grandsire with a wide blaze. Likewise, breeders hoping to avoid body-spotting should not automatically dismiss horses with broad blazes.
I have a few more sabino posts that I hope to finish before returning to recoloring. It is the start of the Spring term, and I am focused on classes, but I plan to continue posting even if it is at a slower pace.