An up-close head-shot of a brown horse, notice the tan coloration of the nose.
A brown foal with her black dam. Notice the darker coloration along the back of her neck and clearly noticeable black points on her legs. Photo courtesy of Greenlich Connemaras
The foal as an adult horse. Notice the tan coloration in the flanks and along the belly. Because her dam is black she is heterozygous for At. Photo courtesy of of Greenlich Connemaras
Seal brown Holsteiner filly: Notice the darker coloration along the neck even though she lacks black on the legs.
A bay foal: Notice the lack of “smuttiness†along the topline and also the lack of noticeable black points. Photo courtesy of Ancient Oaks Sport Horses
A black foal: this shade of black foal coat is sometimes confused with brown but notice the more uniform coloring. . Photo courtesy of Ancient Oaks Sport Horses
A black foal with a faded muzzle. Notice the difference in coloration between the faded areas on the black foal and the tan areas on the brown Photo courtesy of Greenlich Connemaras
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.
Because of this advance, we now know that brown is caused by a mutation on agouti and, is in fact, separate from bay. The brown mutation is denoted At and is recessive to the wild type mutation (A). The order of dominance for the known agouti alleles is A, At,a. This means, that as long as the horse is allowed to express black pigment, (ie not ee) a horse with a genotype of AAt will be bay based while a horse that is AtAt or Ata will be brown based. (I use the term “based†because other dilutions, modifiers or white patterns may still be present.) With the availability of a test for brown, one trend has come apparent, horses that are heterozygous for the brown mutation (Ata) are visually darker than brown horses who are homozygous for the brown mutation (AtAt). At first this may seem a bit counterintuitive but, think of the heterozygous horse (who will be darker) as being closer to black than the homozygous horse. It is also important to remember that while chestnut or sorrel based horses do not express brown they can still carry the brown mutation. It can then be passed on to their offspring and may express if the offspring inherits the right combination of genes from the other parent.
Visual identification of the brown horse can at times be challenging. It can be difficult to tell a very dark brown horse from a faded black horse or a light brown horse from a bay horse. During the winter a brown horse will often fall into the “almost†black category, usually with a brown muzzle and/or flank. During the summer however, they will often lighten to “almost†bay. The affect can be compounded if the horse also fades during the summer. This color change frequently causes confusion among owners who aren’t sure what color their horse truly is.
The brown horse will most often be born with an intense foal coat. This can include darker points and usually a darker topline, while the bay foal will generally have only black pasterns or may even lack black points completely. A bay foal will also have a much lighter coat without the darker coloration along the topline. The difference between a brown foal and a black foal is similar. A brown foal will be born with darker coloration along the topline while the black foal can be born looking anywhere from “mousey†to “brown†to solid black but will generally be a more uniform color. Differences in adult coloration can be even more dramatic. During the winter a brown horse may be almost completely black but will have lighter areas in the “soft†parts of the body with the nose and flank area being the most common. Black horses that fade may look brown but the brown “fade†will be a different shade and these faded areas will generally disappear with the winter coat while the tan areas on a brown horse will remain and may even intensify during the winter months. At first, it may appear easier to distinguish a bay from brown however; a dark bay can be almost indistinguishable from a light brown. A very general rule of thumb is that a Bay will generally have a red tint to the coat and lack the general “smuttiness†that tends to accompany brown, while brown horses will lack this red tent and will instead appear to have tan highlights on a darker coat. It can take time and experience to confidently identify brown from black or bay and even experienced horse people can be fooled. Hopefully, as the test from Pet DNA Services is more widely utilized, some the ubiquity that has long surrounded brown will begin to fade.
A classic example of frame on a chestnut horse. Notice how the white is confined to the barrel, has jagged edges, and leaves the legs solid. Photo Courtesy of Ancient Oaks Sport Horses
Homozygous tobiano stallion with frame. He is homozygous for black as well. An example of how frame can "hide" in other patterns. Photo courtesy of Emily West
A good example of just how minimal frame can be. Although rare, it is necessary for breeders to be acknowledge the fact that frame can be extremely minimal. He has been DNA tested positive for Frame (LWO). Photo is courtesy of Celtic Mist Miniature Horses
The sad result of a frame to frame breeding. This foal was humanly euthenized when he began showing signs of distress. In this case the owner knew her mare was positive for frame but had been assured by the stallion owner that his stallion was negative. As you can see that was not the case.
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. Lethal White Overo foals are born almost solid white with blue eyes. They are born with an under-functioning digestive track which results in sever colic 24-72hrs after birth. Only foals who carry two copies of the frame gene will be "Lethal White" therefore, both parents must be carriers. Since, 25% of frame to frame breedings will result in a lethal white foal, never take someones word that their stallion is negative for frame. If your mare is positive for frame always ask to see the stallions test results. If you are considering buying a mare and the owner states she is negative for frame again, ask to see the test results. If they really have tested they won't mind sharing the result. If they haven't tested well...you can test yourself. The only case where a test would not be necessary is if a horse's sire and dam have both tested negative for frame. Since neither parent carried a copy of the frame gene the foal (or horse as the case maybe) cannot be positive for frame. Breeding frame to frame will never increase your chances of getting a colored foal. It does increase your chances of a dead foal. In any frame to frame breeding there is a 25% chance of getting a frame negative foal, a 50% chance of getting a frame foal, and a 25% chance of getting a dead foal (ie. Lethal White). In frame to solid breedings these numbers change to 50% frame foal and 50% negative frame foal. Notice the lack of a dead foal. The 50% chance of frame stays the same. If your mare (or stallion for that matter) carries frame and you want to maximize your chances of getting white pattern on your foal, breed your frame pattern horse to a tobiano or sabino (who is negative for frame of course). It is possible to get a solid white foal that is not Lethal White Overo. These foals are dominant white, maximum sabino, or carry multiple patterns. The frame pattern is caused by a missense mutation in the gene EDNRB. Testing is available from both UC Davis and Animal Genetics Visit the Frame Photo Gallery
Possible- Based on phenotype
American Saddlebred
American Warmblood
Australian Draught Horse
Australian Stock Horse
Azteca
Campolina
Criollo
Curly
Falabella
Gelderland
Missouri Fox Trotter
Morgan
National Show Horse
Quarter pony
Known Breeds- based on phenotype and testing
American Paint Horse
American Quarter Horse
American Indian Horse
American Shetland Pony
Miniature Horse
Mustang
Nokota
Spanish Mustang
Spotted Kentucky Mountain Saddle Horse
Spotted Saddle horse
Tennessee Walking Horse
Thoroughbred
*This list was complied by CMHorses on this forum thread http://colorgenetics.info/equine/content/horsepony-breeds-frame
