Daylene Alford's blog

In the beginning we had Sabino and Sabino was good and we loved it. We attributed markings to it...alot. It was was our favorite scape goat. “It's Sabino!” was often heard

The KIT gene is responsible for a multitude of white spotting patterns across many species. One of the latest to be discovered is a de novo mutation (a genetic mutation that neither parent possessed nor transmitted) in the Weimaraner Dog.

Tobiano is probably the best recognized of all the white patterns. It almost always leaves the legs white. It will cross the top line at the shoulders and hip before other areas and fights to leave the chest, flanks and head colored. It commonly results in a solid head and white tale head. Some theorize that Tobiano doesn't add face white but whether this is true or not is still open for conjecture. When Tobiano is mixed with other patterns we can get a solid white or nearly white horse but rarely, if ever, does Tobiano express to that extent alone. When Tobiano is very minimal (sometimes called Crypt-Tobiano). It will usually express as four white stockings or socks, sometimes with a wither or neck spot. In miniature horses, it's expression can found at it's most minimal, at times leaving only the back two feet white.

The color brown in horses has long been a source of ambiguity. Some registries handle brown as a separate color, while others consider all browns to be dark bay. Adding to the confusion, researchers, even as late as 2003, theorized that the darkest brown horses were actually black horses with mealy. It became apparent however, when the recessive allele at agouti (a) was located, that these dark horses with brown noses and flanks didn’t test as black but as bay. Because no other agouti alleles were located, at the time, it was generally accepted that brown (even the almost black variety) was just a darker version of bay. This changed when Pet DNA Services of Arizona isolated the mutation that causes brown.

Frame is a white pattern in horses that puts white on the barrel and the face of a horse. It tends to leave white markings with jagged edges but no "halos" (areas of dark skin under white hair) or roaning. Frame can cause blue eyes and face white but prefers to leave the legs solid. Horses positive for frame can have leg white, but it must be added by a separate white pattern. Any color horse can be a frame carrier and frame's expression can very greatly from a "solid" animal to one who is wildly marked. Frame will rarely cross the top line of the horse without another white pattern being present. Because of frame's wildly varying expression, as well as its ability to "blend" with other patterns, it can be very difficult to tell if a horse carries frame simply by visual inspection. Frame is the gene responsible for Lethal White Overo Syndrome. It is therefore important, for everyone who may breed a frame positive horse, to understand how frame is inherited and how it affects foals.

During fetal development cells called melanocytes migrate out from the spinal cord to other areas of the body. These melanocytes produce the pigment that “colors” the dogs coat and skin. Areas where the melanocytes do not reach during fetal development remain without pigment causing areas of white hair and pink skin. The areas most commonly white in dogs are the last areas that are reached by the melanocytes: the chest, tip of the tail, and the toes. The current theory on white pattern development is that environmental factors in the womb (and perhaps white booster or suppressor genes) can affect melanocytes migration resulting in small white spots in these areas without an actual white pattern mutation. When mutations occur in the genes that control melanocyte migration, large areas of white can result. Recent studies have shown that at least one white pattern is the result of a mutation in the gene microphthalmia-associated transcription factor (MITF). However, this mutation does not account for all the white patterns found in canines and in some dogs the mutation does not follow the expected pattern indicating additional genes at work. (Schmutz et al. 2009)

It's quite common for countershading to be confused with dun markings. What is countershading? It's not known what causes countershading type markings but they are believed to be a type of camouflage. Countershading is more common on foals but can appear on adult horses as well. Countershading markings that can closely resemble dun are false dorsals, shoulder bars, and stripes or mottling on the legs. It is usually possible for a trained eye to distinguish between the two even on foals but at times even experts can be fooled. The most important thing to remember is that a dun foal must have a dun parent. It is sometimes possible for dun to "hide" in that it can be covered by gray or white patterns but generally speaking if the horse has no dun in its near pedigree then it's not dun but countershading.

Horses are non-ruminants meaning that unlike cows and goats they only have one stomach. They also are unable to regurgitate food. This mean they can't "throw up" if they eat something that is poisonous or something that upsets their stomach. It is therefore important to only provide high quality feeds and forage.