Splashed white or splash is a horse coat color pattern in the "overo" group of spotting patterns that produces pink-skinned, white markings. Many splashed whites have very modest markings, while others have the distinctive "dipped in white paint" pattern. Blue eyes are a hallmark of the pattern, and splash may account for otherwise "solid" blue-eyed horses. Splashed white occurs in a variety of geographically divergent breeds, from Morgans in North America to Kathiawari horses in India. The splashed white pattern is also associated with congenital deafness, though most splashed whites have normal hearing. Splashed white can be caused by multiple variants across two different genes, for which genetic testing is available. [1] [2]
The splashed white pattern is characterized by the appearance of having been dipped, feet-first, into white paint. Blue eyes are common, but not universal. [3] [4] [5] [6] The margins of the white markings are crisp, smooth, blocky, and well-defined. [7] [6] The head and legs are white, and the tail is often white or white-tipped. [7] [5] [6] The underside of the body is white, and a connected white patch often spreads smoothly up either side of the thorax. [6] On its own, the splashed white pattern is seldom responsible for white markings that reach the topline, and so it has been categorized as one of the "overo" patterns by Paint horse and Pinto horse registries. [3]
The minimal expression of the splashed white pattern can include few or no white markings at all. When only minimal markings are present, other qualities can belie splashed white. Stars and snips may be lopsided, off-center, or otherwise strangely placed. Blazes are usually blocky or straight-edged, and bottom-heavy. Splashed white blazes may also be crooked or skewed to one side. [5] Sabinos with a bold blaze almost invariably have white on the lip or chin, and this is not the case for the facial white of a minimally marked splash; the upper lip typically remains colored. [5] [8] Leg markings in a minimally marked splashed white range from hind coronets to high-whites on all four, or marked hindlegs and unmarked forelegs. While sabino leg markings are often tapering with distal patches, the leg markings on a splashed white usually have crisp borders. [3]
The most reliable identifier of the splashed white pattern is one or more blue, or parti-colored eyes. [7] [3] [5]
Some breed registries make a distinction between pinto horses and solid horses which may have white markings.
Breed registries for which minimum or maximum white markings are a factor in registration have created imaginary lines to simplify the selection process:
White markings extending past these lines are considered "pinto", "paint" or "colored" while white markings which do not cross these lines are not considered to suggest these traits. However, horses without "excessive white markings" can still have the potential to produce "high white" or distinctly spotted offspring. Splashed white horses have produced generations of "solid" horses, followed by an errant, classically marked splashed white. Discreetly marked splashed whites are responsible for some families of cropout American Quarter Horses. [3] [4]
As sabino-type markings also originate on the underside, some splashed whites can be mistaken for cleanly marked sabinos. [7] Both patterns can be present on the same horse, but splashed white markings are crisp and blocky, and horizontally distributed. In particular, the face markings of splashed whites are straight-edged and bottom heavy, whereas those of sabinos are often tapering or feathered, and often vertical in orientation. Splashed white markings also generally have smoother edges than sabino. [7] The presence of additional white patterning genes can intensify the amount or obscure the characteristics of splashed white markings. [4] [5]
In the Gypsy horse, the pattern called "blagdon" is described as "a solid colour with white "splashed" up from underneath." [9]
Potential health concerns involving splashed white are deafness and, for some rare variants, embryonic viability.
There is some association between splashed white and congenital deafness in horses that are very white, though many or most splashed white horses have normal hearing. [4] [3] [8] [10] This type of deafness is probably similar to instances of deafness in white or piebald, blue-eyed examples in other species. In white-coated cats and dogs with deafness, an absence of melanocytes in the inner ear leads to death of the hair cells, which are necessary for perceiving sound. [10] The presence of pigment around the outside of the ears - which most splash horses have - does not prove the presence of that necessary pigment in the inner ear. There must be pigment inside the inner ear to prevent this problem. [2] Domestic horses often cope well with deafness, and deaf horses may go undiagnosed. Some deaf horses are more skittish than normal, while others are distinctly calmer. Deafness in horses can be diagnosed by brainstem auditory evoked potential (BAEP), which is minimally invasive and requires no sedation and minimal restraint. [10] While blue eyes and a white face are often associated with deafness in other species, apron-faced, non-splash horses are not known to be deaf. Nor is the presence of one blue, one normal eye indicative of unilateral deafness. The case horse in Hardland's 2006 case study had one blue eye, while the other was parti-colored, but the horse was bilaterally deaf. [10]
Some variants of splashed white may produce non-viable embryos if homozygous. SW1 and SW2 have been found in homozygous form, but SW3, SW4, SW5, and SW6 may or may not be homozygous lethal. [4] [1] [2] At present, this cannot be ruled in or out.
In other species, changes to PAX3 (where SW2 and SW4 are found) can cause cleft palates and other congenital defects. [11]
DNA tests exist for six forms of splashed white across two different genes. SW1, SW3, SW5, and SW6 are alleles of MITF, while SW2 and SW4 are alleles of PAX3. [1]
SW1 is the most common known variant. It is incomplete dominant, meaning it has different effects depending on whether one copy or two copies are present. Horses heterozygous for SW1 (one copy) may have a minimal splash pattern, or may be completely solid. Horses homozygous for SW1 (two copies) have the more extensive classic splashed white pattern. [5] [12]
The splashed white pattern was first studied in Finnish Drafts and Welsh ponies by Klemola in 1933. [13] He divided pinto patterns into a dominant "piebald", describing patterns now known to come from tobiano, frame overo, and sabino, and a recessive "splashed white". His splashed white appears to be describing only the more extensive form of the pattern seen when two copies of SW1 are present.
Originally believed to be very rare outside of Europe, splash is turning out to be more common than previously thought, possibly due to the pattern's tendency to masquerade as modest markings. For example, minimally marked splashed whites have been responsible for cropouts among American Quarter Horses. [3]
There may be additional forms not yet mapped. In addition to breeds identified as carrying the SW1, -2 or -3 alleles, color patterns described as splashed white but not yet verified via genetic testing have also been identified in American Saddlebreds, Shire horse, Clydesdales, and the Irish Tinker or Gypsy horse. [3] [4] [5]
It is likely that many splashed whites go unidentified, whether because their markings are too minimal to register as "pinto" with breeders, confusion with sabino, or the confounding effect of multiple white spotting patterns. [3] [5] Just as the presence of additional white patterning genes can increase the amount of white, other genes may be responsible for restricting the expression of splash. [5]
The genetic mechanisms behind certain traits, such as blue eyes in a few Arabian horses with otherwise minimal markings, have yet to be identified, though there is speculation that splash genes could be involved. [14]
Informal name | Technical name | Gene |
---|---|---|
SW1 | MITFprom1 | MITF |
SW2 | PAX3C70Y | PAX3 |
SW3 | MITFC280Sfs*20 | MITF |
Macchiato | MITFN310S | MITF |
SW4 | PAX3:p.Pro32Arg | PAX3 |
SW5 | MITFdel | MITF |
SW6 | SW6 | MITF |
SW7 |
SW1 is the most prevalent. It appears to be several hundred years old and predates the development of modern breeds. SW1 has been identified in the American Quarter Horse, American Paint Horse, Icelandic horse, Miniature horse, Morgan horse, Shetland pony, Trakehner, and Finnhorse. [15] [18] [19]
SW2 is a PAX3 mutation mistakenly thought to originate with a single Quarter Horse mare foaled in 1987. However, it seems it is actually older, and it has been found in Quarter Horses and Paint horses as well as Noriker and Lipizzan horses. [18] [20] [21]
SW3 has been exclusively found in certain lines of Quarter horses and Paints, and is very rare. [2] [4] [18]
Another allele of splash informally called "Macchiato" has only been found in a single Franche-Montagne horse, probably a spontaneous mutation, and that individual was sterile. [4] [15]
SW4 was found in a family of Appaloosa horses. [16]
SW5 was found in a family of American Paint Horses. [17]
SW6 is thought to originate with a dual registered Paint horse and Quarter horse stallion. [12]
Some horses of Quarter Horse lineage carry more than one splash mutation. [4] [15]
The American Paint Horse is a breed of horse that combines both the conformational characteristics of a western stock horse with a pinto spotting pattern of white and dark coat colors. Developed from a base of spotted horses with Quarter Horse and Thoroughbred bloodlines, the American Paint Horse Association (APHA) breed registry is now one of the largest in North America. The registry allows some non-spotted animals to be registered as "Solid Paint Bred" and considers the American Paint Horse to be a horse breed with distinct characteristics, not merely a color breed.
Waardenburg syndrome is a group of rare genetic conditions characterised by at least some degree of congenital hearing loss and pigmentation deficiencies, which can include bright blue eyes, a white forelock or patches of light skin. These basic features constitute type 2 of the condition; in type 1, there is also a wider gap between the inner corners of the eyes called telecanthus, or dystopia canthorum. In type 3, which is rare, the arms and hands are also malformed, with permanent finger contractures or fused fingers, while in type 4, the person also has Hirschsprung's disease. There also exist at least two types that can result in central nervous system (CNS) symptoms such as developmental delay and muscle tone abnormalities.
Lethal white syndrome (LWS), also called overo lethal white syndrome (OLWS), lethal white overo (LWO), and overo lethal white foal syndrome (OLWFS), is an autosomal genetic disorder most prevalent in the American Paint Horse. Affected foals are born after the full 11-month gestation and externally appear normal, though they have all-white or nearly all-white coats and blue eyes. However, internally, these foals have a nonfunctioning colon. Within a few hours, signs of colic appear; affected foals die within a few days. Because the death is often painful, such foals are often humanely euthanized once identified. The disease is particularly devastating because foals are born seemingly healthy after being carried to full term.
A piebald or pied animal is one that has a pattern of unpigmented spots (white) on a pigmented background of hair, feathers or scales. Thus a piebald black and white dog is a black dog with white spots. The animal's skin under the white background is not pigmented.
Skewbald is a colour pattern of horses. A skewbald horse has a coat made up of white patches on a non-black base coat, such as chestnut, bay, or any colour besides black coat. Skewbald horses which are bay and white are sometimes called tricoloured. These horses usually have pink skin under white markings and dark skin under non-white areas. Other than colour, it is similar in appearance to the piebald pattern. Some animals also exhibit colouration of the irises of the eye that match the surrounding skin. The underlying genetic cause is related to a condition known as leucism. The term is also used to describe spotting patterns in various other animals, such as goats.
Tri-coloured refers to a horse with three different coat colours in a pinto spotting pattern of large white and dark patches, usually bay and white. This colouring is also commonly called skewbald. In modern usage in British English, skewbald and piebald horses are collectively referred to as coloured, while in North American English, the term pinto is used to describe the colour pattern.
Bay is a hair coat color of horses, characterized by a reddish-brown or brown body color with a black point coloration on the mane, tail, ear edges, and lower legs. Bay is one of the most common coat colors in many horse breeds.
A gray horse has a coat color characterized by progressive depigmentation of the colored hairs of the coat. Most gray horses have black skin and dark eyes; unlike some equine dilution genes and some other genes that lead to depigmentation, gray does not affect skin or eye color. Gray horses may be born any base color, depending on other color genes present. White hairs begin to appear at or shortly after birth and become progressively more prevalent as the horse ages as white hairs become intermingled with hairs of other colors. Graying can occur at different rates—very quickly on one horse and very slowly on another. As adults, most gray horses eventually become completely white, though some retain intermixed light and dark hairs.
A pinto horse has a coat color that consists of large patches of white and any other color. Pinto coloration is also called paint, particolored, or in nations that use British English, simply coloured. Pinto horses have been around since shortly after the domestication of the horse.
Tobiano is a spotted color pattern commonly seen in pinto horses, produced by a dominant gene. The tobiano gene produces white-haired, pink-skinned patches on a base coat color. The coloration is almost always present from birth and does not change throughout the horse's lifetime, unless the horse also carries the gray gene. It is a dominant gene, so any tobiano horse must have at least one parent who carries the tobiano gene.
Overo refers to several genetically unrelated pinto coloration patterns of white-over-dark body markings in horses, and is a term used by the American Paint Horse Association to classify a set of pinto patterns that are not tobiano. Overo is a Spanish word, originally meaning "like an egg". The most common usage refers to frame overo, but splashed white and sabino are also considered "overo". A horse with both tobiano and overo patterns is called tovero.
Horses exhibit a diverse array of coat colors and distinctive markings. A specialized vocabulary has evolved to describe them.
A white horse is born predominantly white and stays white throughout its life. A white horse has mostly pink skin under its hair coat, and may have brown, blue, or hazel eyes. "True white" horses, especially those that carry one of the dominant white (W) genes, are rare. Most horses that are commonly referred to as "white" are actually "gray" horses whose hair coats are completely white. Gray horses may be born of any color and their hairs gradually turn white as time goes by and take on a white appearance. Nearly all gray horses have dark skin, except under any white markings present at birth. Skin color is the most common method for an observer to distinguish between mature white and gray horses.
Sabino describes a distinct pattern of white spotting in horses. In general, Sabino patterning is visually recognized by roaning or irregular edges of white markings, belly spots, white extending past the eyes or onto the chin, white above the knees or hocks, and "splash" or "lacy" marks anywhere on the body. Some sabinos have patches of roan patterning on part of the body, especially the barrel and flanks. Some sabinos may have a dark leg or two, but many have four white legs. Sabino patterns may range from slightly bold face or leg white markings—as little as white on the chin or lower lip—to horses that are fully white.
Markings on horses are usually distinctive white areas on an otherwise dark base coat color. Most horses have some markings, and they help to identify the horse as a unique individual. Markings are present at birth and do not change over the course of the horse's life. Most markings have pink skin underneath most of the white hairs, though a few faint markings may occasionally have white hair with no underlying pink skin. Markings may appear to change slightly when a horse grows or sheds its winter coat, however this difference is simply a factor of hair coat length; the underlying pattern does not change.
Rabicano, sometimes called white ticking, is a horse coat color characterized by limited roaning in a specific pattern: its most minimal form is expressed by white hairs at the top of a horse's tail, often is expressed by additional interspersed white hairs seen first at the flank, then other parts of the body radiating out from the flank, where the white hairs will be most pronounced. Rabicano is distinct from true roan, which causes evenly interspersed white hairs throughout the body, except for solid-colored head and legs.
A cropout, crop-out or crop out is a horse with body spots, including pinto or leopard complex spotting, or "high white" horse markings, with a sire and dam who both appeared to have been solid-colored. There are several variations in the definition, depending on the breed registry involved. There are multiple genetic reasons that may cause a horse to be a cropout. Sometimes solid-colored horses throw cropouts because some spotting patterns are recessive genes that are not necessarily expressed unless the relevant allele is inherited from both parents. Other times a gene may be a dominant or incomplete dominant but so minimally expressed that the horse looks solid but can pass flashy color on to its offspring.
Dominant white (W) is a group of genetically related coat color alleles on the KIT gene of the horse, best known for producing an all-white coat, but also able to produce various forms of white spotting, as well as bold white markings. Prior to the discovery of the W allelic series, many of these patterns were described by the term sabino, which is still used by some breed registries.
The Pinto Horse Association of America (PtHA) registers horses, utility horses, ponies and miniature horses of various pedigrees with certain kinds of pinto coat colors. The word pinto is Spanish for "paint." In general terms, pinto can apply to any horse marked with unpigmented pink-skinned, white-haired areas on its coat. The Pinto Horse Association of America provides the owners and riders of pintos with a show circuit and a breed organization. The primary requirement for PtHA registration is coat color; the pinto is not a true breed, but a color breed.
Roan is a horse coat color pattern characterized by an even mixture of colored and white hairs on the body, while the head and "points"—lower legs, mane, and tail—are mostly solid-colored. Horses with roan coats have white hairs evenly intermingled throughout any other color. The head, legs, mane, and tail have fewer scattered white hairs or none at all. The roan pattern is dominantly inherited, and is found in many horse breeds. While the specific mutation responsible for roan has not been exactly identified, a DNA test can determine zygosity for roan in several breeds. True roan is always present at birth, though it may be hard to see until after the foal coat sheds out. The coat may lighten or darken from winter to summer, but unlike the gray coat color, which also begins with intermixed white and colored hairs, roans do not become progressively lighter in color as they age. The silvering effect of mixed white and colored hairs can create coats that look bluish or pinkish.