Why Overo Isn't Specific Enough
by Leslie Kathman

Many times we see horses on someone’s sire/dam list that are described as "overo". The problem with this is that it isn’t very specific; it does not give a person looking for parents enough information to determine if the horse would be a suitable choice. That is because there are three separate kinds of overos, each of which are the product of separate, distinct genes. This means that an overo of one type cannot produce foals of the other two overo patterns, unless they are bred to a horse that does have that pattern. So listing a model as an "overo" is about as helpful as just saying the model is "spotted" or "pinto"-- what kind of overo is vital information!

Frame Overo

Frame overo is the classic overo pattern. Most of the "rules" for telling overos from tobianos (white does not cross the back, legs and tail are dark, ect.) come from this pattern. Ironically, it is also the rarest pinto pattern! Because it is not found in the European or Asian breeds, it is thought to be a mutation that occurred in the New World. It is also the pattern that is thought to be responsible for "lethal whites" when a horse inherits two frame genes, it is born entirely white and dies shortly after birth.

The most visible difference between frames and other overos is that frames have dark legs. Often frame overos will have no white on their legs, or will have one or two small socks. Invariably, if you find a frame overo with one or more stockings, he is also carrying the sabino gene. They also tend to have dark toplines and dark manes and tails. They have bald faces, but not to the same extent that splash-whites do. An entirely white head will often mean that they are also carrying the splash gene. Frames will occasionally have a blue eye; the trait is more common in frames then in sabinos, but far less common than in splashes. Along with the bald face, white is generally concentrated on the neck and sides, usually in fairly large patches that will often have jagged edges similar to torn paper. A few have lacy edges and some will have large, crisp edges. Often the hindquarters will remain dark, or with very little spotting.

The only breed where frame overos are found in any numbers is the Paint. There have been true frame overo American Miniatures, and there was even a line of frame overo Morgans that has since been lost.

Sabino Overos

Where frame overo is the rarest overo pattern, sabino is the most common; just about any breed that does not restrict white markings to "small stars and socks" will have sabinos to varying degrees. Usually, the more the breed is inclined to flashy markings, the more likely it is to find sabinos, making the pattern quite rare in a breed like the Morgan, and almost universal in a breed like the Clydesdale.

Because it occurs in so many breeds, many of which do not officially allow pintos, and because it often expresses itself in such a minimal way (high stockings and belly spots, for example), sabino is often discounted as a pinto pattern. Many breeders will write off as "flashy markings" or "high white", or even classifying it as a type of roan. Nonetheless, it is still a pinto pattern -- as is proven by the occasional wildly pattered foal from such parents!

One of the things that does make this pattern difficult is that there is a great deal of variation among individuals and from breed to breed. Some sabinos have crisp, ragged edged patterns, while others are a blotchy roan. In some breeds, the pattern is strongly linked to the chestnut color, while in others it occurs on all colors equally. In some the mane and/or tail are affected, making them roan or even -- in the case of bays -- flaxen, but in others the mane and tail remain dark. There are, however, a few characteristics common to most sabinos, which include blazes that tend to extend over the muzzle and under the jaw (the other overos tend to spread across the face towards the cheeks, rather then under them), high stockings that travel up the stifle, disconnected knee patches and spotting that starts on the belly or girth area. Roaning is more common in this pattern than in any other, while blue eyes are extremely rare (they are far more common on model sabinos than in real ones!) It is also possible to get entirely white sabinos, which usually have dark eyes.

Again, almost all breeds without marking restrictions will have some sabinos, regardless of whether or not the registry "allows" pintos. Breeds where it is common include the Tennessee Walker (it was the original color of the breed), Missouri Fox Trotter, Clydesdale (there are not, to my knowledge, Clydesdales that do not have the pattern!), Paint, and the Gelderlander. It is also common in certain strains of Arabians, Welshes, Quarter Horses, and American Shetlands.

Splash Overo

Not as common as sabino, but not nearly as rare as frame, splash overos are the ones that break nearly all the "rules" regarding overos. Unless the horse is predominantly dark, the white will cross the back, and the edges are almost always crisp and rounded, like a tobiano, and the tail is often white, as are the legs. For this reason, some splash overos are mistaken for tobianos. Others are mistakenly labeled toveros. But splashes are a category of overo all their own, and are characterized by a lot of white on the face (often the entire head is white) and white on the legs and underside -- making the horse appear to have been splashed into a bucket of white paint. Another telltale sign of the pattern is blue eyes; splashes invariably have one or more two blue eyes, even when they are only minimally marked. Splash is also similar to sabino in that it often is so minimal that it appears as if the horses have flashy markings, when they are genetically pintos.

Splash overo occurs in a wide variety of breeds, often in the form of unexpected crop-outs. It does appear in Quarter Horses, Paints, and even Appaloosas, especially those tracing to Old Fred. It is quite common in Welsh Ponies, where blue eyes are considered by some to be a hallmark of "old blood", although obvious pintos are no longer granted papers. It s also found in Icelandics, Shetlands, Tennessee Walkers, Saddlebreds, Missouri Foxtrotters, and Finnish Drafters.

Combination Overos

As was mentioned, all three overo patterns are the product of separate genes. This means that a horse can inherit one, two, or even three different overo patterns (and even the tobiano pattern as well -- these are the "toveros"). Combination overos take the characteristics of each pattern they possess, so they might have the all-white face of a splash overo, along with the lacy edging and roaning typical of a sabino, for example. This can make the patterns in these horses particularly hard to identify. Also making it harder is the fact that combination overos often have a great deal of white (since each pattern has white in a different area, each pattern that is added gives more white). So much white will sometimes hide the clues that would otherwise give away which pattern(s) were involved.

Combination overos (and toveros) are most common in breeds where pintos are sought after, since "high white" horses are rarely bred together in breeds that have color restrictions. In breeds like the Paint, where all types of patterns are found and where they are frequently bred together, the majority of horses will actually have more than one pattern.

So overo is really a general term that simply means "pinto that is not a tobiano". And as you can see from the descriptions, many of the "rules" people use to tell an overo from a tobiano can actually lead to mistakes in identifying a horse. This is because the rules are generalizations about three very different patterns, and not all of them apply to each pattern. Some of these rules include "white does not cross the back" (it does on many splash-whites, and on some sabinos), "some of the legs will be dark" (not always true on splashes or sabinos), "the tail is dark" (splashes often have white tails, and sabinos often have mixed or flaxen tails), "they have blue eyes" (very uncommon in sabinos) and "the edges are lacy or ragged" (not true of splashes and even some frames). While they cannot be condensed into a few simple rules, the descriptions above are much more accurate ways to identify the patterns.

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