Pinto Patterns
Pinto Patterns: Pinto is a term that refers to several different patterns of white. The patterns fall into two catagories,
tobianos and
overos. The overo catagory is really just a catch-all for non-tobiano patterns that includes frame overo, sabino, dominant white, and splash white. A horse with a combination of tobiano and one or more overo patterns is known as a
tovero.
The
tobiano pattern is dominant, and it is characterized by white crossing the horse's back between the withers and the dock, as well as by areas of color on the head, chest, and flanks. Most tobianos have normal face markings like stars and blazes, and they almost always have four white feet. The most minimally marked tobianos occasionally appear to have only 4 stockings and no other discernable white markings.
Frame overos are characterized by having a dark topline between the withers and dock, with blocks of white on their sides and necks. Frame overos usually have large blazes or apron markings.The feet are usually dark, but may be white if combined with other pinto patterns, particularly sabino. The frame gene is responsible for "lethal white overo." Horses that are homozygous for the pattern (2 copies) die shortly after birth. Heterozygous frames are perfectly viable.
(See below.)
Sabino is a pattern that comes in many forms. In its minimal form, it only manifests itself as small socks and a star or blaze, if that. More extreme sabinos will have white patches, often with roaned edges, creeeping up their sides from the underside of the belly. The most extreme sabinos will look entirely white or nearly so, often retaining a few patches of color along their toplines, particularly on the ears or in the mane.
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. Like frame overo, dominant white is believed to be lethal in its homozygous state, but it is lethal early on in utero.
Splash white horses look as if they've literally been splashed with white paint from the underside or dipped in white paint. Splash white is an incomplete dominant. Homozygous spashes will have more white than heterozygous splashes. Splash markings tend to have smooth, crisp edges, and most splashes have blue eyes (especially the homozygous ones).
Most pinto patterns can range from minimal expressions (a nearly solid colored horse) to extreme expression (an all-white or nearly all-white horse). White horses resulting from tovero and sabino patterns are completely viable. White horses that are homozygous for frame overo, however, are known as lethal white overos (LWO). For more information on lethal white, please read my page about
white horses.