Skewbald is a colour pattern of

horse The horse (''Equus ferus caballus'') is a domesticated, one-toed, hoofed mammal. It belongs to the taxonomic family Equidae and is one of two extant subspecies of ''Equus ferus''. The horse has evolved over the past 45 to 55 million y ...

s. A skewbald horse has a coat made up of white patches on a non-black base coat, such as

chestnut The chestnuts are the deciduous trees and shrubs in the genus ''Castanea'', in the beech family Fagaceae. They are native to temperate regions of the Northern Hemisphere. The name also refers to the edible nuts they produce. The unrelat ...

, bay, or any colour besides black coat. Skewbald horses which are bay and white (bay is a reddish-brown colour with black mane and tail) 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 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 backgro ...

pattern. Some animals also exhibit colouration of the irises of the eye that match the surrounding skin (blue eyes for white skin, brown for dark). The underlying genetic cause is related to a condition known as

leucism Leucism () is a wide variety of conditions that result in the partial loss of pigmentation in an animal—causing white, pale, or patchy coloration of the skin, hair, feathers, scales, or cuticles, but not the eyes. It is occasionally spelled ' ...

. The term is also used to describe spotting patterns in various other animals, such as goats.

Horses

Terminology

In British equestrian use, ''skewbald'' and ''

'' (black-and-white) are together known as ''coloured'', and the white markings are called ''patches''. In North American equestrian usage, the term for all large-spotted colouring is ''

pinto Pinto is a Portuguese language, Portuguese, Spanish language, Spanish, Sephardi Jews, Jewish (Sephardic), and Italian language, Italian surname. It is a high-frequency surname in all List of countries and territories where Portuguese is an officia ...

'', and the markings are called ''spots'', The specialized term ''

paint Paint is any pigmented liquid, liquefiable, or solid mastic composition that, after application to a substrate in a thin layer, converts to a solid film. It is most commonly used to protect, color, or provide texture. Paint can be made in many ...

'' refers specifically to a breed of horse with American Quarter Horse or

Thoroughbred The Thoroughbred is a horse breed best known for its use in horse racing. Although the word ''thoroughbred'' is sometimes used to refer to any breed of purebred horse, it technically refers only to the Thoroughbred breed. Thoroughbreds are c ...

bloodlines in addition to being spotted, whereas ''pinto'' refers to a spotted horse of any breed. Americans usually describe the colouration of a pinto literally: black-and-white, chestnut-and-white, or bay-and-white.

Genetics

Genetically Genetics is the study of genes, genetic variation, and heredity in organisms.Hartl D, Jones E (2005) It is an important branch in biology because heredity is vital to organisms' evolution. Gregor Mendel, a Moravian Augustinian friar working i ...

, a skewbald horse begins most commonly with a chestnut base coat colour (called "red" by

geneticist A geneticist is a biologist or physician who studies genetics, the science of genes, heredity, and variation of organisms. A geneticist can be employed as a scientist or a lecturer. Geneticists may perform general research on genetic processe ...

s), or some other set of colour genes other than black. Then the horse has an

allele An allele (, ; ; modern formation from Greek ἄλλος ''állos'', "other") is a variation of the same sequence of nucleotides at the same place on a long DNA molecule, as described in leading textbooks on genetics and evolution. ::"The chro ...

for one of three basic spotting patterns overlaying the base colour. The most common coloured spotting pattern is called

tobiano 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 c ...

, and is a

dominant gene In genetics, dominance is the phenomenon of one variant (allele) of a gene on a chromosome masking or overriding the effect of a different variant of the same gene on the other copy of the chromosome. The first variant is termed dominant and t ...

. Tobiano creates spots that are large and rounded, usually with a somewhat vertical orientation, with white that usually crosses the back of the horse, white on the legs, with the head mostly dark. Three less common spotting

gene In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a ba ...

s are the frame and splash

overo 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 ...

genes, which create a mostly dark, jagged spotting with a horizontal orientation, white on the head, but dark or minimally marked legs. The sabino pattern can be very minimal, usually adding white that runs up the legs onto the belly or flanks, "lacy" or roaning at the edge of the white, plus white on the head that either extends past the eye, over the chin, or both. The genetics of overo and sabino are not yet fully understood, but they can appear in the offspring of two solid-coloured parents, whereas a tobiano must always have at least one tobiano parent.

Other animals

The term is also applied sometimes to

goat The goat or domestic goat (''Capra hircus'') is a domesticated species of goat-antelope typically kept as livestock. It was domesticated from the wild goat (''C. aegagrus'') of Southwest Asia and Eastern Europe. The goat is a member of the a ...

s and

dog The dog (''Canis familiaris'' or ''Canis lupus familiaris'') is a domesticated descendant of the wolf. Also called the domestic dog, it is derived from the extinct Pleistocene wolf, and the modern wolf is the dog's nearest living relative. Do ...

s, among other animals. Both ''piebald'' and ''skewbald'' are used in dog and goat breeding.

References

"Introduction to Coat Color Genetics"
''from'' Veterinary Genetics Laboratory, School of Veterinary Medicine, University of California, Davis. Web Site accessed January 12, 2008

External links