Tag Archives | Tarpans

An interesting example of splashed white

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Like I mentioned in the previous post, I became an avid collector of any examples of splash I could find. One of the most interesting “finds” I made was this particular foal, April’s Spumoni.

She appeared in the American Tarpan Studbook. I should caveat the title with the statement that while these horses were called “Tarpans” at the time, in actual fact they were not exactly Tarpans. Authentic Tarpans have been extinct since the last one died in a Russian zoo in 1909. Here is the last known photo of a living Tarpan, taken in 1884.

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The Tarpans in the book are more accurately called Heck Horses. They are so named for the German biologists, Heinz and Lutz Heck, famous for their theory that extinct animals could be recreated by back breeding. That is, they felt that the genetic material that remained in domestic descendants of the original horses could be concentrated through selective breeding, until something approaching a true Tarpan was obtained. In addition to the Tarpans, they attempted to recreate the extinct Auroch.

The work of the Heck brothers is very controversial. The projects, which were conducted at the Tierpark Hellabrunnin in Munich, are often said to have been Nazi-funded. But perhaps more importantly from a genetic standpoint, there are problems that extend beyond the initial premise, which was itself controversial from the start. Questions remain about just how accurate was their understanding of the animals they were trying to recreate. (To be fair, the existing information they had to work with was itself questionable. The Tarpan pictured above, for instance, is thought by some to be of questionable origin.) It is also said that their research was not transparent; the details of what crosses were used were not preserved. Lacking modern molecular tools, they were also limited to what they read in historical accounts, and what they could see in the (alleged) domestic descendants.

Those are a whole lot of qualifiers to say that the little filly at the top was not really a true Tarpan, and may not have actually had any Tarpan blood in her makeup. It would be a mistake to say that she is proof that splashed white originated among the Tarpans, and made its way from there to domestic animals. Not when two of the breeds believed to be utilized by the Heck brothers were the Icelandic and the Gotland, both of which have modern individuals that have tested positive for the SW1 mutation.

But her situation does have something potentially interesting to tell us about splashed white.

I was surprised to find a splash in that stud book, to say the least. Her minimally-marked parents were even more puzzling. At the time I obtained my copy of the studbook, most of the splashed white horses I had found were from American breeds (Paints, Saddlebreds) or Welsh Ponies. I had not even begun to suspect that the pattern was incompletely dominant, and I had not yet encountered Gotlands Ponies and the way the patterned appeared among them. (I had seen and handful of Icelandic individuals, but was not able to track their backgrounds.) April’s Spumoni was a puzzle, because her parents were so minimally marked. They were both marked with white, which was why they both appeared in the Appendix of the studbook. Her sire had one white coronary band and a small snip. Her dam had a tiny star and a small snip. If Gambling Man has parents that left me scratching my head because I couldn’t figure out which was the culprit, Spumoni was puzzling because I could not imagine how either could be the culprit. They had “ordinary” markings.

That was close to 20 years ago, when I still imagined that there were “ordinary” markings. Markings that did not mean anything. Needless to say, I gave that idea up some time ago. Markings, and what they mean, is the question that drives most of my personal research these days. Back when I first encountered Spumoni, I wondered whether something was tamping down the pattern on her parents, or whether something was amping up the white on her. Initially I overlooked the possibility that it could very well be both, and that the range of patterns out there were being subtly altered by all kinds of boosters and suppressors.

Which is why I think Spumoni is all the more interesting in light of some of the most recent tests. I had noted in the past that some of the seemingly homozygous splash horses (what we would now assume to be SW1/SW1) had parents with almost no white. As more horses turn up with really conservative parents, it is interesting to ask just how minimal can a heterozygous SW horse be when no white boosters are present. It is certainly true that some of the Gotland parents are quite minimal. What was true about Spumoni is that she came from horses solid enough to pass for the regular register, which required that horses be unmarked. Her parents were marked, of course, and that placed them in the Appendix. All four of her grandparents, though, were registered as unmarked. In the cases where photos are available, the individuals look truly solid. Spumoni also had a full sister that had white feet, and her sire had a full sibling with a blaze and socks. All these horses trace back to unmarked horses. It is possible, of course, that the zoos involved misidentified the horses when compiling the studbook. (The early horses were all the property of zoos.)  Still, it was a small breeding community, with a small group of founder animals, so it seems unlikely that several of the more influential founders were falsely described as unmarked.

As more horses are tested, we may find out just what those outer limits are. The idea that we may start getting clues about what causes markings on horses is very exciting. That is the big puzzle, after all.

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Musings about markings

I have time for just one more post before I go on my internet sabbatical, so I thought I’d leave off with some musings about white markings.

My friend Caroline Jones shared this photo of a partbred Suffolk with me recently. She is interesting because her sire is a solid chestnut (“whole-coloured”) Suffolk, and her dam was a bay Shire. She has a large star and what looks like some white hairs on her nose. Although they are not visible in the photo, she had completely solid black legs.

The two breeds are interesting because modern Shires are uniformly marked with white, and are likely homozygous for some kind of sabino. British Suffolks, on the other hand, have been heavily selected for the absence of white on the legs. Even in the early stud books (late 19th century) leg white was rare and usually pretty minimal, but over time the preference for solid legs eliminated even that. They can have face white, and some even have blazes, though solid faces or small stars are the most common. The Shire and the Suffolk are therefor at the opposite ends of selection for markings.

What is an interesting question is why the absence of markings won out, at least in this case. If sabino is dominant, then a homozygous sabino should stamp all its foals with some type of sabino marking. Is this mare, with her large star and dark legs, a sabino? And does this mean that the absence of markings might also be more than just that? Do Suffolks carry something in addition, something that limits the white? Chestnut is considered quite a ‘leaky’ color when it comes to white markings, so much so that chestnut outcrops from unmarked black or bay breeds often have white that their darker relatives never displayed. It makes sense that to create an (largely) unmarked chestnut breed like the Suffolk, breeders would have inadvertently concentrated white suppressing genes.

The idea of white suppressors has long interested me. I first came to wonder about them when I ran across a splash overo crop-out (reconstructed) Tarpan. At the time I wondered how such a loud foal could come from two minimally marked parents. The sire had a small snip and a white coronary band on a hind foot, and the dam had a tiny star and small snip. Was something tamping down the white on the parents? Or was something boosting the white on the foal? Since then I have come to believe that, in the case of splash, the parents were typical of heterozygotes in breeds without ordinary white markings. Although it might not have been relevant to the Tarpans, I have come to suspect that the answer to my original question about boosting and suppressing is that both happen.

So is Susie (above) a suppressed sabino, or a boosted star-marked horse? And just what do those suppressors and boosters do to other patterns? How many of each kind are there? Is there a separate suppressor for faces and for legs? (We know there are breeds uniformly marked with sabino-like face markings, but no leg markings, for instance.)

When I return from my break, I’ll get back to dominant whites (and their connection to the zebra topic).

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