Sabino (or sabino overo) is a pinto pattern that is extremely common in Thoroughbreds. It is a pattern of white hairs imposed on any coat color that ranges in expression from minimal to maximal. In its most minimal form, it is often manifested as simply a blaze and stockings. More boldly marked sabinos will have white splashes on their bellies and sides, often with roany edges, and the most extremely marked sabinos can be all white or nearly so. Marquetry, pictured below left, is an excellent example of the moderate form of this pattern. as are Northern Dancer and many of his descendants. Note the left hind stocking which seems to come to a point as it rises up Marquetry's leg---this is very typical of the sabino pattern. Also notice the odd white spot on his left knee. Sabinos tend to have odd spots like this one on their bellies as well. The sabino pattern tends to be more loudly expressed on chestnut and chestnut-based colors like palomino.
The sire Northern Dancer is an excellent example of a typical minimally marked sabino. .
The stallion Marquetry is also a fairly minimally marked sabino. Note the odd spot on his left front knee and his blaze that extends on to his chin, both typical sabino indicators.(Photo by Tony Leonard)
Dominant White is a pattern that was for a long time thought to be part of the sabino gene complex. Like sabino, the amount of white on the coat can vary, though most dominant white horses tend to be heavily patterned or nearly all white. Interestingly, dominant white is frequently found to be the result of a mutation, so loudly marked foals can result from otherwise plain parents. Dominant white is believed to be lethal early in utero in its homozygous state. Recent genetic testing has shown that several TB families thought to be sabinos are in fact dominant whites. They include Puchilingui (Sato, etc) and White Beauty (Patchen Beauty, The White Fox, Patchen Prince, etc) and probably others like Shirayukihime (dam of Yukichan and 3 other white horses), Turf Club, Our White Lady, etc.
Phenotypically, sabinos and dominant whites are essentially indistinguishable. Genetic testing is required to prove which a horse is.
This horse is the late Puchingui, sire of many modern dominant white TBs. (Photo by Dan Trout)
This is The White Fox, an extreme sabino son of Patchen Beauty. His first four dams tail-female are white extreme sabinos.
The frame overo pattern does exist in the Thoroughbred gene pool, but it is limited to only a handful of family lines. The only frame overo TBs cropped up in the last 20 years. All are from relatively obscure lines, and the presence of the pattern may be due to a random mutation. In TBs, frame is almost always seen in conjunction with the sabino pattern which makes for some spectacularly patterned horses. Horses carrying only the overo gene almost always have four dark legs. White legs on a horse also carrying frame overo usually indicates sabino at work.
The splash white overo pattern has only recently been recognized in the Thoroughbred. Though there have been a few isolated reports of potential splash whites, no good examples were found until a mare named Hey What The in New Zealand produced two unique fillies in 2003 and 2004. As with the frame pattern, the origins of splash in TBs are mysterious. In heterozygous form, splash can be very minimal, as little as a small snip on the nose, so it likely has flown under the radar for so long because of this.
Seeing Spots: Birdcatcher Spots, Chubari Spots (aka Tetrarch Spots), Bend Or Spots, and Manchado These odd patterns of dark and light spots do occur in other breeds, but they seem to be particularly prolific in the Throughbred, which is why most of them are named after TBs. The genes responsible for these spots have not yet been identified, so not a great deal is known about them. They are, however, entirely seperate from the genes responsible for Appaloosa coloration.
Birdcatcher spots or ticks are patterns of small white spots on a dark coat. Usually, these spots appear once a horse has reached maturity and eventually disappear. Sometimes, however, they do seem to be permanent. This is Willspynow, a 1991 mare by Well Selected out of Spy Gail, by Father Hogan. This mare's spots are bigger and more highly concentrated than most Birdcatcher spots. (Photo by Barbara Livingston)
| Chubari spots (also sometimes called Tetrarch spots) are similar to Birdcatcher spots except that they tend to be much larger. They are usually egg-shaped and egg-sized, as seen here on The Tetrarch. They seem to be tied to the grey color, but they are different from dapples. Dapples can change and fade as the horse ages, but chubari spots don't disappear until the horse has completely greyed out. Many grey TBs have a few chubari spots but it is unsual to see a horse with as many as The Tetrarch. | |
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Bend Or spots are random dark spots on a horse's coat. Man O' War, a descendant of Bend Or, is said to have had these spots. Pictured is Commendable, the 2000 Belmont winner, who has a Bend Or spot on his right hip. Bend Or spots seem to show up most frequently on chestnuts and chestnut-based colors, like palomino, but they can occur on other colors. (Photo by ?)
This pattern is known as manchado or "manchado overo." It has only cropped up in Argentina in a handful of horses from various breeds (Criollo, Hackney, Arab, and TB so far). Because it is only found in Argentina and it has not proven to be hereditable, it may be the result of environmental factors rather than genetic ones. There is also some thought that it may be an exceedingly rare recessive gene. The pattern is not known to be related to other spotting patterns like the appaloosa pattern or Bend Or spots. The horse pictured is a Thoroughbred,Royal Manchado, a 1990 stallion by Royal Castle (ARG) out of Kleymary (ARG), by Manchester (ARG). |
All information and pictures are taken from www.whitehorseproductions.com |
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