Tobiano and overo refer to two color patterns used to describe pinto-colored horses. Pinto-colored horses have patches of solid colors, such as black, bay, or chestnut, interspersed with patches of white. Think of an overo as a solid-colored horse that had an unfortunate accident with a paint bucket; someone splashed or dabbed random patches of white on the horse's sides. A tobiano often looks like a solid colored horse that had a bucket of white paint poured all over his back; the paint dripped down the back and sides, but left some solid-colored patches showing. Learning to distinguish between the two color patterns can be confusing at first, but with practice, you can learn the distinction between the two coat patterns.
Overo and tobiano coat patterns can occur in horses or ponies of any size. The overall appearance of the two coat patterns differs in the amount and placement of the white patterns on the horse's body. A tobiano horse has white patches crossing the horse's spine, which extends from the spot between the ears, called the poll, down to the tip of the tail bone. On a tobiano horse, the white pattern will cross over the spine at any point. An overo horse has a mostly solid-colored body with white patches, which can be quite large, that do not cross the spine at any point. An overo horse's mane and tail usually are dark, while a tobiano may have white mixed in with the mane and tail color.
Face and Eye Color
Overo horses often sport the striking white pattern on the face, called a "bald" face. A bald-faced horse has a large mask of white extending over the eyes and across the entire head down to the muzzle. Bald-faced horses often have blue eyes, a feature often found among overo-patterned horses. Tobiano horses usually have a solid-colored head and typical horse face markings, such as a white star, snip or stripe. They usually have brown eyes if the solid color appears on the face near the eyes.
Leg and Hoof Color
Another difference between an overo and tobiano coat pattern is the color of the legs and hooves. The leg color of an overo horse usually is dark and matches the body color. An overo patterend horse with a predominantly solid bay color may have the usual black markings on the legs that are found on bay horses. The hooves typically are a beige or grayish-beige color. Tobiano horses usually have white-colored legs, and some tobiano horses have black hooves. Black hooves are not required, however, for a horse to be considered a tobiano.
The overo and tobiano patterns are carried by a color gene. Tobiano is a dominant gene, meaning that a horse sporting a tobiano pattern must have at least one parent carrying the tobiano gene. Genetic tests are available that can determine positively an overo or tobiano pattern. According to the Australian Paint Horse Association, the test for tobiano horses looks for the dominant "T" gene. The test to determine if a horse carries the overo gene is called the OLWS test. Unless you plan to breed your horse, it probably is not important to obtain a genetic test to determine whether it is an overo or tobiano.
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