Archive | Splash white

Names, categories and descriptive terms

TobiTypical

FrameTypical

I believe that often a seemingly illogical system makes sense when its history is considered. Because revelations are often gradual, systems build on what came before. In this way you often end up with something that is less ideal than what could have been devised had a more accurate picture been known from the start. I believe that knowing this is essential to understanding where things stand today with the terminology for pinto patterns.

When I first took an interest in horse color, most American horsemen accepted that there were two kinds of pinto patterns: tobiano and overo. Those were the terms used by the American Paint Horse Association, which was the largest registry for pinto-patterned horses. If you read enough horse magazines, eventually you would run across a list of rules for determining whether or not a horse was a tobiano or an overo. Did the white cross the topline? Tobiano. Was one or more legs dark? Overo. Did the horse not follow either set of rules? Then he was a combination of the two – a tovero. The rules were useful if you had a typical tobiano or a pure frame overo like the one pictured above.

They were slightly less useful for minimal tobianos like this one.

MiniTob

But the real limitation came when dealing with any of the other pinto patterns. Splashed white, for instance, actually followed the tobiano rules more closely than those for overo. The truth was that the rules for “overo” could be more accurately said to be the rules for frame overo. The rules described that very specific pattern, but in actual practice the term overo was being used to mean anything not tobiano.

In the 1970s and early-1980s, a number of writers began to include additional pinto categories. Among these were splashed white (which had been described in still earlier literature) and sabino. In the United States, Paint Horses with these patterns were registered as overos, so the convention became that, aside from tobiano, the “new” patterns were different forms found under the general category of overo. Thus there was a frame overo, sabino overo, and splashed white overo. Later, when it was identified and named, there was manchado overo. This convention can be a source of frustration for breeders in other countries where overo has been used pretty exclusively for frame overo. (The fact that frame overo is one of the better-known lethal genes probably adds to the desire not to see the same word tacked on to the back of other pattern names.) It makes more sense if it is understood that this was a way of integrating new information into a widespread, existing naming system. It was easier to tell the many breeders of Paint Horses that they needed to be more specific about which type of overo they had, rather than tell them that they had been wrong for calling all those non-tobiano horses overo in the first place.

Categories of Patterns

That process has repeated itself a few times in the years since. We start out with patterns that have names, and then find out we have unwittingly placed genetically different things together under one name. So the name becomes a category, rather than one specific pattern. This has meant it was necessary to search for a way to distinguish between the patterns within the new category. With the advent of genetic tests, the most common approach has been to number the different variations. So when it became clear that Splashed White was a category of patterns, and not one specific pattern, the variations were given numbers in the order in which they were discovered: Splashed White-1, Splashed White-2, and so on through to (at the time of this writing) Splashed White-5.

Although the speed of new discoveries made it difficult for many to adjust, the system has worked reasonably well, with one big exception. That exception is Sabino.

I have written before about my own involvement in researching sabino patterns. In the 1990s, an article I wrote speculating that many white-born horses were in fact “maximum” sabinos was widely circulated on the internet. While I came to that conclusion primarily using research on the Tennessee Walking Horse, I really was just rediscovering what the Dutch researcher J. K. Wiersema already knew in the 1960s. The pattern we both were studying is now known as Sabino-1. With that specific pattern, heterozygous Sabino-1 horses have flashy white markings with roaning, and homozygous Sabino-1 horses are white. We both also observed, however, that there seemed to be other kinds of sabinos that did not look quite like this. What’s more, those patterns did not seem to have a connection to white horses. We both also noted that there were white-born horses that did not quite fit the profile. In hindsight, it is clear that this should have been a big clue that too many different patterns were being lumped into this one category.

This problem is quiet obvious if you group images of horses with patterns that have been called sabino in the past. Here is a slide I used in a recent presentation that makes this point in a very visual way. All the horses in this image have patterns that would, at one time, have been referred to as sabino.

SabinoSlide

Given the broad range of white patterning in that image, it would not be surprising that many began to consider sabino a pattern category. Within that category, or group, one might expect to find quite a lot of separate patterns. And that was what many expected, after the first sabino pattern (Sabino-1) was identified. The assumption was that researchers had found the first of what was likely quite a large number of them. Certainly it was clear that what was arguably the most common form of sabino – what many breeders refer to as “flashy white” – was not the one that had been identified. Although Sabino-1 was later found to be quite an ancient pattern, in modern times it is found in a rather limited range of breeds. It was expected that some of the more common types of sabinos would soon follow.

FlashySab
Horses like this one, with flashy white stockings, a blaze, and maybe a bit of white on the belly or girth, have long been thought of as the most common form of sabino

That expectation did not come to pass. The next set of patterns that were formally identified were classified as Dominant Whites and given the names White-1 through White-4. Each of these particular mutations resulted in horses that were, in terms of phenotype, either completely white or nearly all-white. Because the idea that white-born horses were “maximum sabinos” had gained a lot of traction in the years prior, there were some that felt those first four patterns should have been part of the sabino category, picking up the numerical sequence at Sabino-2. The truth was that those first patterns did fit the original definition of Dominant White in that they produced their own color 50% of the time, and the mutations appeared to be homozygous lethal. The fact that some of the individuals with those mutations were not entirely white would not have actually come as a complete surprise to earlier authors who wrote about Dominant White. Almost every account of the color mentioned the tendency to throw “pied” foals along with white ones. It did make sense to classify those mutations as White rather than Sabino.

When more patterns were added to the White category, the difficulty with the terminology increased. That was especially true with some of the later patterns that looked far more like what had traditionally been called Sabino. Some breeders working with the bloodlines where the more patchy expression was common referred to their horses as Sabinos in advertising. This stallion, Sato, from the Puchilingui line (W-5) of Thoroughbreds, is a good example.

Sato1

For someone interested in producing pinto-patterned sport horses, advertising a horse as Sabino makes good sense, because most pinto breeders do not actually want a white horse. Indeed, some registries for colored horses will not issue regular papers for white horses; they are considered “solids”. Did breeders know that a horse like Sato was technically White? Yes. And the line did produce all-white horses on occasion. But most were loudly patterned in a way that would, at least at one time, be called Sabino.

Officially, however, these horses were White, popularly known as Dominant White. For the sixteen patterns of this type that were discovered after those initial four, each was named as part of the W series of mutations. It was assumed that any other mutations found in that same region were likely to continue in this fashion, while nothing else would be added to the Sabino series. In this way, Sabino could be said to have gone from a named pattern, to a category of patterns, to an informal term used to describe a specific pattern on a specific horse (much like the way roaning is used). Put another way, sabino became the official name for one specific pattern (Sabino-1), and an unofficial descriptive term for some individual horses with patterns of some other official name.

That was roughly where things have stood until very recently, as reflected in the chart below.

NameChart

That seemed to be the system that would continue, until researchers got to W-20. That is where the naming system became a bit harder to explain, because there have been unexpected twists in the most recent discoveries. Because things get a bit more complicated from here, I am going to break this across to a second post. This one has already run quite long (even for a blog that routinely breaks the “keep it brief” rule of blogging!) and there is a lot to digest. I also want to pull the next part out because a study is currently being organized that touches on these new developments, and I want to give that the space it deserves. With luck, I will get the next part out in a more timely manner than this one!

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Searching for another founder

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An elderly Finnhorse, descendent of the stallion Eversti

In the previous post about founders, I talked about the search for the origins of the silver dilution. I wanted to present another case study that highlights some of the challenges in tracing color lines, this time with classic splash white (SW1). We tend to talk about this form of splash white as being incompletely dominant, with the heterozygous horses tending to show very little white and the homozygous horses having the more distinctive “classic” form of the pattern. When the pattern was first described in 1931, however, it was called Recessive Pied. This was in contrast with Dominant Pied, which we now call tobiano. Later the author, Valto Klemola, proposed changing Dominant and Recessive Pied to “Piebald” and “Splashed White” respectively.

By visiting the Splashed White Project page, and clicking on the button to display heterozygous SW1 horses, it is easy to see why Klemola would have considered the pattern recessive; the horses in that group do not look like pintos. In fact, there is a growing understanding that in breeds with minimal white markings, horses can carry the SW1 mutation without showing unusual – or sometimes any – white or blue eyes. With that reality in mind, classic splash behaves enough like a recessive that it illustrates how the search for a founder is different when the color is not visible in the carriers.

Klemola noted how the pattern sometimes surprised breeders.

In the native breeds of Northern Europe what at first glance looks like a piebald foal may be produced from quite normally-colored parents. This surprising phenomenon has given rise to many fantastic explanations among the breeders…

That observation comes from the second paper, published in the Journal of Heredity in 1933. The earlier paper, published in Zeitschrift für Züchtung, included pictures of Danish and Swedish horses with the classic splash pattern. But the main focus was on the Finnhorse stallion Eversti, who was known for producing both blue eyes and occasional pinto patterns. Although he was only mentioned in passing in the 1933 paper, the earlier one provided extensive details about both his ancestors and his descendants, all of which point to the likelihood that he was heterozygous for SW1. Eversti was a black horse with white markings, but his paternal great-granddam was a blue-eyed pinto (“glasäugig und bunt”). When dealing with historical records, SW1 horses are rarely identified as pintos unless they are homozygous. Had the color been unique to Finnhorses, she could not have been the founder. One truth about recessive colors is that the founder would not actually be the new color. Remember each specific mutation is a one-time event. To display a recessive trait, an animal must be homozygous – it must have two of the same mutation. So even if his pinto great-grandmother had been the first known splashed white, she could have been ruled out as the actual founder. The real founder appears somewhere on both sides of her pedigree, and he or she was probably quite unremarkable. The original mutation could spread pretty far before two descendants were crossed, and the result was a very obvious pinto.

Klemola knew that splashed white was not unique to the Finnhorse, so that unnamed pinto mare was never considered as the founder. As he noted, the same pattern occurred in other Northern European breeds, so the original mutation happened before those breeding groups separated. In more recent times, the same type of pattern was observed in breeds as diverse as the Pasos of Puerto Rico and the Marwaris of India. When a pattern is found across a broad range of breeds and regions, that usually means that the mutation is old. Like other old mutations – silver, tobiano, leopard complex – it is unlikely that much will ever been known about the horse that carried that first SW1 mutation.

OregonIceOnFire
Oregon Ice On Fire, a descendant of the Morgan mare Royal-Glo, is heterozygous for SW1

The most that may be possible is to identify some of the sources for the pattern within some of the modern breeds. Now that a test is available for the pattern, carriers can be identified even when they have not produced the more obvious classic pattern. With enough testing information, lines that carry SW1 can be identified. This process has already started in the Morgan breed, where Royal-Glo and Lady In Lace, and ultimately their ancestor Rhythm Lovely Lady, have been named as likely sources. It may be possible from there to connect those horses to some of the early American lines that predated the stud books, since some of those were noted for producing blue eyes. This is perhaps as far back as it may be possible to go with the history of the pattern in America. 

In the case of the Finnhorse, Eversti proved to be an influential stallion. His great-great-grandson, Murto, is one of the four male lines in the breed. Both Murto and his son, Eri-Aaroni, were chestnuts with flashy white markings. Intiaani, the first Finnhorse that tested positive for one copy of SW1, carried 21 lines to Murto through the female side of her pedigree alone. Eleven of those were though Eri-Aaroni. And yet that influence is probably the best argument against the color coming from Murto. It is difficult to find a modern Finnhorse without multiple lines to Murto – and by extension, to Eversti. If Murto carried SW1, breeders should have started to see classic splash offspring among his linebred descendants. Yet until the results came back from Intiaani’s test, it was widely assumed that the pattern could no longer be found in Finnhorses. That would suggest that the source for the mutation came through one of the less common lines to Eversti, or even one of the other lines that go back to Eversti’s sire Jalo (grandson of the blue-eyed pinto mare). The flashy white on Murto and Eri-Aaroni may well be unrelated to SW1.

800px-Eri-Aaroni_and_Paavo_Nurmi
Eri-Aaroni, a son of Murto and one of the most influential stallions in the Finnhorse breed

There are quite a few horses that have either tested positive for a single copy of SW1, or that have produced the classic pattern, that look like Eri-Aaroni (pictured above). A fair number of the known splash white producers in the Welsh Mountain Pony have similar markings. There are also quite a few breeds where these types of markings are common, like the Arabian, yet SW1 is not believed to be present. That complicates the search for sources in breeds where a variety of white-producing mutations are found – which is actually the case in most breeds. Even the presence of blue eyes in a line may not indicate the presence of SW1 in breeds where it is known to be, because some blue-eyed horses have been testing negative for the (currently) known forms of splash white.

With luck those other blue-eyed horses will prove to have a newer mutation. That is the case with the other four formally identified forms of splashed white. The founder of the most common of those, SW2, is a known individual. While she was not named outright in the original paper, the information given matched that of the 1987 Quarter Horse mare, Katie Gun, dam of the famed reining horse, Gunner. The suspected founders of the other three were all born in the last two decades, which would suggest that mutations of this type are more common than originally thought.

And this is probably a good place to jump over to the subject of my friend’s albino dog, since that involves recessive genes, separate mutations producing similar colors, and the search for founders. I’ll start that topic in the next day or two.

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Another minimal classic splash

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Hairicane Lil Bit Rowdy, Miniature Horse mare

Here is another interesting splash white that is homozygous for SW1, sent in by Robin Cole. Unlike the Gotland in the previous post, this mare does have blue eyes, but the white on her face is quite minimal. Like the Gotland, she has four white feet, but all but one leg are very minimally marked. Her pattern looks even more minimal when seen from her other side, probably because the skew in her blaze keeps most of the white away from this side of her face. 

HairicaneLilBitRowdy2

Although she comes from a line that carries frame (Oh Cisco), she tested negative for that pattern. And while she might look tobiano, especially to readers familiar with how tobiano often skews in Miniatures and Shetlands, neither parent is a tobiano. They do look like heterozygous splashes, and the family is known to produce splash patterns. In fact, this is her full sister.

LilBitRowdyFulSis

So while homozygous SW1 horses are pretty consistent in appearance, minimized patterns can be found. That seems especially true among the breeds – like the Gotlands, Icelandics, Shetlands and Miniatures – that are already known to minimize the tobiano pattern. Here are links to a few interesting examples of minimal homozygous SW1 from those breeds:

Bládís vom Moarschusterhof, an Icelandic mare with what appears to be one dark front leg
Hnísa vom Römerberg, an Icelandic mare, also with a seeming dark foreleg
Unun frá Efri-Úlfsstöðum, an Icelandic mare with an irregular blaze and minimal white
Glæta frá Ártúnum, an Icelandic mare with a large star, large snip and what may be a dark eye
(with each of these links, you can click on the first image to pull up additional images)

Opp, a Gotland mare with a face marking much like the one on the Miniature in this post
She does have a more extensive body pattern, though.

And finally, while it is not a minimized pattern, this Gotland mare Nanna does have an unusual skew to her pattern. Along with minimizing the white, skewing patterns seems to be another (relatively) common aspect in this group of breeds.

I had intended to do a post on blue eyes and negative splash tests, but I think it makes more sense to shift that post to after the ones about white markings since those two things are closely related. I am also going to take a little detour into blue eyes of a different kind, though, before tackling the markings. Watch for that in the next day or two. And if you have not done so already, you can get notifications of new posts to the blog via email by filling out the subscription form in the right hand sidebar. I apologize to long-time readers that had a subscription before and now have to re-subscribe, but that was the one thing that did not transfer with the blog when it was moved to a self-hosted site.

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