Tag Archives | frame overo

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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Belton pattern on the feet

ACCFilly

In yesterday’s post, I included Audrey Crosby McLellan’s mare, AC’s Painted Lace. The belton spots are pretty obvious on her face, and I wondered if there were similar spots on her white legs. Audrey was kind enough to provide pictures that show them very well.

These first two images are with the lower legs clipped, so they show the spots very clearly. Like the spots on the faces of the previous horses, they are very round and have the same kind of halo effect where the underlying dark skin is wider than the colored hair.

LaceysLegs2 copy
Those images show the markings very clearly, and these are good shots of wet feet to show what is going on with the hooves.


Right front foot (front and back)


Right hind foot (front, side and back)


Left hind foot (front and back)

These pictures show how the color is concentrating down around the hoof. This kind of density in spotting is often seen in tobianos, where the cat-tracks cluster around the hoof. This gives some tobianos surprisingly dark hooves. It is also seen in some belton dogs. They have heavier spotting on the legs (and face), but it increases still more at the toes. Here is a tobiano with that kind of spot concentration, and an inset image of an English Setter with the black-toed belton look.

darktoes

I have no idea if the actual mechanism behind belton dogs (T, or Ticking) is even similar to these kinds of spots on horses, but the visual similarities are striking.

I would also add that posting unusual horses to the blog is a lot of fun, because it often results in readers sending in images of their own horses, or horses they have encountered. Just recently, someone sent a horse that is truly strange – and it takes a lot for me to call something strange! I am going to use the leg spotting as a jumping-off point to talk a little about cat-tracks, and then move on to my strange example. So stay tuned for some cool stuff!

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Belton patterning and frame overo

HesStyling

The above image of a belton patterned face is from the contents page of the most recent Paint Horse Journal. I didn’t notice the title until I scanned it so I could add it to my research files. It certainly does seem that lately there is a horse with this type of patterning “in every issue”!

The horse pictured is the Paint stallion Hes Stylin. He is a good example of the type of belton ticking that seems to be linked with the presence of the frame pattern. Like the pattern in some dogs, this type of dark ticking concentrates more heavily on the face, where the spots are more numerous and generally larger than on the body.

BeltonComp

(English Setter picture courtesy of Wikimedia Commons.)

Since making the initial few posts about what I called belton patterning (for lack of a better term, since “ticking” already means white hairs in the coat), many people have sent pictures and links to horses with these kinds of markings. I have also begun noticing the less dramatic versions that I had previously overlooked. The more I see of ticked horses, the more I believe that this particular type is probably linked to frame. That doesn’t explain a horse like Vision Morinda, or the more heavily cat-tracked tobianos, so I suspect there is more than one cause of dark spots on markings or patterns. The frame overos with belton patterning, though, seem to have a pretty consistent look.

The spots are very round, and often have more colored skin than colored hair, which gives many of them a ghosted or haloed appearance. This type of effect is noticeable on the cluster of spots close to Hes Stylin’s left eye.

The white patterning on the body does not really show a lot of these round spots, though most have had some. I’ll return to Gump, the first horse I posted, to show both sides of his pattern. The round spots on his face contrast quite markedly with the ragged nature of his pattern. The link to Hes Stylin (above) shows a full-body picture, and he has the same kind of contrast between the torn outline of his pattern and the regularity of the spots.

GumpRight

GumpLeft

I apologize that I don’t have a better photo of Gump’s left side. I try to get conformation shots of both sides on patterned horses, but sometimes the opportunity never presents itself. It’s not a flattering picture, but that left shot does show how much clear white there is on the body pattern relative the the spotting on the face.

Gump does have some belton spots on his lower legs, though they are not as pronounced as on his face. Most dogs that have this type of belton pattern have bolder spotting on the lower legs as well as the face. The image of this English Setter puppy (also courtesy of Wikimedia Commons) illustrates that effect, though the underlying black-and-tan pattern makes her feet look paler because the base color there is tan.

800px-English_Setter_Spain

Because frame overos do not typically have a lot of white on the lower legs, it is hard to know if the spots would concentrate there or not. In fact, many of the examples I have encountered or have been sent have no white on the legs at all. Here is a mare I photographed at a fun show last fall. A different photo of her appears in the book to illustrate the frame pattern in what is probably its pure form.

BeltonFrame3

Her legs are all dark, but here is her face. The spots are not nearly as pronounced on her as on Gump and Hes Stylin, but that seems to be true of most of the chestnuts with these types of spots.

BeltonFrame1

BeltonFrame2

What is interesting is that this mare also has what looks like a large occluding spot above her right eye. For that matter, it is possible to think of the patch over her eye, and the one across her muzzle, as occluding spots. If you look at Hes Stylin up at the top of the post, he has a similar set of patches above his eye, too. A similar spot is present on this Paint cross mare, Hechzeba, shared by Audrey Crosby McLellan of ACC Photography.

ACC3

She is tested positive for frame, but has no body white (or leg white) to show any further spotting.

hechzeba

Audrey also sent a link to pictures of her own mare, AC’s Painted Lace, who was also tested to carry the frame pattern. Notice how she has a patch over the eye and on her nose that are quite similar to the earlier mare.

ACCFilly

In photos it looks like Lacey has some spotting inside her socks, but even her face spotting is more subdued than some of the others. It may be that is due to other white patterning, since some white patterns (like some forms of sabino) are known to amplify the white on the horse at the expense of colored areas. It also might be that this particular kind of spotting is just concentrated on the face. Until there are more examples with leg white, it is hard to know for sure. And even then, it is hard to know if the factor that put the white on the legs (where it is usually missing on frames) might not also erase the spots there. That may be what happened with Hes Stylin, since he has what appear to be unspotted legs.

(Hes Stylin is also interesting in that his is the combination of frame with another pattern that is most often mistaken for tovero. Although the dark areas fall in such a way that it is an easy mistake to make, his sire is an unmarked Quarter Horse (Kids Classic Style) and his dam is a overo mare (Shesa Scotch Bar Doll) from a long line of overos.)

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