Notebooks are the heart of my research. They contain information on horses of interest – their colors, markings, photos, pedigrees – arranged four-up (more or less) on a page. Over the years, I have filled thousands of pages. They look like this:
There are a handful of topics that have tended to fill my notebooks in the last few years. I wanted to use this particular topic, recoloring, to show why the kind of record-keeping in the notebooks is so useful to me.
My interest in recoloring started with Gump (pictured above). I saw him at a local Paint Horse show, and the roan spots inside his face marking immediately caught my attention. Muzzle spots, even densely-placed muzzle spots, are not uncommon on certain kinds of pintos. Gump’s spots were unusual because they were relatively large and spread across the entire length of his face. Those spots raised questions in my mind. White spotting is, by definition, the absence of the cells that produce pigment. Were there factors that could restore those cells to those areas? Was it possible to “recolor” an unpigmented area?
Those questions stuck with me, and I began to look for more horses like this. Gump was a frame overo with a modest pattern (pictured below). I wanted to see if this was something linked to the frame pattern. Was it found on horses with other pinto patterns? Could it appear on non-pintos?
Once I started looking, I found spotting like this on other kinds of pintos and non-pintos as well. I called the markings “belton” after the coloring of an English Setter and set up a notebook so I could compare the horses that I found. There were some tendencies that I noticed pretty quickly. For example, a blaze on a belton-spotted horse tended to terminate well before it reached the upper lip. Broken blazes were quite common, and the bottom tended to have a “scalloped” shaped. The Quarter Horse mare below has a very stereotypical blaze for a belton-spotted horse.
Gump’s spots were not confined to his muzzle. I soon noticed that this was also true of the leg spots on tobianos. Ink spots on homozygous tobianos tend to cluster more densely around the coronet. That is also true of garden variety ermine spots. With belton patterning, the spots covered the length of the leg more evenly. (Note the spots on the hind leg on the Quarter Horse mare above.)
This type of record-keeping is also useful is because I can compare trends in the pedigrees. That was what convinced me that the classic form of splashed white – the one found in Welsh Ponies and Icelandics – was incompletely dominant. With belton patterning, pedigrees allowed me to find tobianos where I could rule out homozygosity as the cause for the spots. It has long been known that not all ink-spotted tobianos were homozygous. With the pedigrees alongside the images of the horses, I could start to compare the phenotype of horses where homozygous ink spots had been ruled out with those where it was not. There were subtle visual differences on most of the horses. I could also see horses that appeared to have both types of spots. The horse pictured in the close-up at the top of this post is one of those.
With Sabino-1 and Splashed White-1, the pattern of inheritance was easy to recognize from the records. So far, belton spotting has not been so straight-forward. There are reasons to think it might have a connection with other recoloring traits like badger face and colored socks. At least, some of the families with belton patterns seem more likely to have those kinds of markings than non-beltons. I also think that one of the prevailing theories, that these kinds of markings are due to white suppression, is mistaken. But at this stage, I have more questions than answers. (That is the stage of research I like the best, by the way. Imagining a world where I might never run out of questions makes me happy.)
Like sabino, this is an area that interests me and one that I will explore in future posts. In the meantime, I am still adding horses to my notebooks. If you have a horse with belton spots, a badger face, or a colored sock, I would love to hear from you!
Top photo is © Kimberley Smith and used with permission.