Archive for January 24, 2011

Sunrise 10:02 am, Sunset 4:05 pm for more that 6 hours of daylight, and gaining 6 and a half minutes a day. The gain is fairly steady now, changing by only a couple of seconds a day. The clouds that came in last night to warm things up are clearing, though there were enough left to give a pink sunrise. Temperature 9 below, but the forecast calls for warming this week–highs generally above zero F, lows below 0. Still not much snow–we have a chance Wednesday and Wednesday night, but only a chance. I think all the snow must be down south! At least we have a break from ice fog temperatures.

An updated version of this post is available.

Any color horse, full color, dilute, or with intermixed white hairs, can have white body markings. These have long been recognized as falling into two categories: leopard (Appaloosa in North America) and pinto (or paint, piebald, skewbald, or parti-colored.) I’ll leave the leopard complex for later—maybe Tourist Trap will be out by then, and the horses in it have leopard complex markings. For today, I’ll just give a brief overview of the paint/pinto nomenclature.

Tobiano (left) and leopard (right)

In British usage, a piebald was a black and white horse, and a skewbald was red and white. This distinction is rarely made today. Rather, the color of the horse—bay, black, palomino, red dun roan, or whatever—is followed by the pattern of marking. And there are a lot more patterns recognized today, often due to quite distinct genes, than was the case when I first became interested in horse genetics!

Paint and pinto are in fact synonyms when they are used as descriptive terms, though they have separate breed registries. In North America pinto may be more common in the east and paint in the west, but either may include any of the patterns of white body spotting.

The first breakdown came when tobiano—the pattern shown by the horse in the left of the photo—was recognized as being genetically distinct from overo. Then it turned out that there were several genetically distinct patterns being lumped together as overo—just about everything that wasn’t tobiano, in fact. The latest version of Sponenberg gives no less than seven patterns of white body markings, not including the leopard complex or the dark-eyed solid white of the American Albino. I’ll give a very short summary of the seven here, and cover specific patterns and what is known of their genes in later posts.

Tobiano is a relatively clean, crisp spotting with white legs but generally dark heads. White markings tend to be vertical and generally cross the back in all but minimally marked animals.

The frame pattern was once considered typical overo. It is horizontal, tends to affect the head first and the legs last, and white rarely crosses the spine. Frame to frame breeding can produce white foals that die shortly after birth.

Sabino-1 horses normally have both face and leg markings, and often have roaned areas as well. They are usually not as crisply marked as tobianos, but they vary widely and confusion with almost any of the other patterns is possible.

Splashed white gives the appearance of the horse being splashed with white paint from below. The legs are normally white, and so is the belly area. In addition, white is normally present on the head, often to such an extent that the head is entirely white.

Polygenetic sabino and the form of dominant white that sometimes produces colored areas are not well characterized genetically. but are apparently distinct from the other forms of white spotting.

The final pattern, which is very rare, is called manchado, and has been seen in several breeds in Argentina. In this pattern, white first appears along the top line, and can produce a white mane on an otherwise colored horse. The head and legs tend to stay dark as the white areas grow larger, and there are often dark spots in the white, giving a superficial similarity to some leopard patterns.

All of these patterns vary widely in the amount of white, and all have pink skin under the white portions of the coat. I’ll take them one at a time in later posts.