Roan (color)
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- Different meaning: Roan, Norway.
Roan is a type of coat color in horses (and, occasionally, in other animals, such as dogs and cattle) that is a mixture of white hairs with a base coat of another color.
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[edit] Roan in Horses
Roan, caused by the roan gene, (R), consists of single white hairs intermingled with the base color of a horse. Roaning gives the horse a lightened appearance, while the mane, tail and head tend to remain darker, close to the original base color. Roan horses also tend to have dark lower limbs. It is a dominant gene, meaning that at least one parent must be a roan in order to pass the gene on (it does not appear from two non-roan parents with roan lineage).
- see also Equine coat color genetics
The true roan gene appears in some breeds more than others. Roans are commonly found in Quarter Horses, American Saddlebreds, Tennessee Walking Horses, Connemara Ponies, Miniature horses, American Paint Horses, Welsh Ponies (though rarely, if ever, in Welsh Cobs) and Shetland Ponies. There are only two roan Morgan horses known to be alive today, a gelding and an aged mare, so the color is probably at a dead end in that breed.[citation needed]
The roan gene arguably does not appear in Arabians and Thoroughbreds; though horses in these breeds have been registered as "roan." It is thought that irregularly colored individuals in those breeds may actually carry the rabicano or sabino gene complex rather than the "true" roan gene.
Several terms are used to describe different shades of roan in horses:
- see also Equine coat color
- Red or Strawberry Roan Begins with a chestnut base coat with white intermingled hairs. Like a chestnut or sorrel, the mane and tail are red. Some red roans have so many white hairs as to have a near-pinkish tint while others, tending toward rabicano coloring, may have only a few white hairs intermingled on an otherwise dark coat.
- Bay Roan Begins with a bay base coat, giving a roan horse a reddish coat but black mane and tail, with dark "points" (ears and lower legs). The head will usually be red, with a black forelock. Bay Roans are sometimes also called red roans. [1]
- Blue Roan Begins with a black base coat, intermingled with white hairs and the end result is a horse coat with a bluish tint. Blue roans are occasionally confused with grays or a blue . However, a gray becomes lighter with age and a blue roan does not. A blue dun (also known as a grullo) has a faded mouse-colored coat that is all one shade on the body (other than the distinctive dun markings), with no intermingled white hairs.
These shades of roan are created genetically as follows:
- Red base (chestnut "e" gene) + Roan = Red or Strawberry Roan
- Black base ("E" gene) + Roan = Blue Roan
- Bay base (Black ("E" gene) + Agouti "A" gene) + Roan = Bay Roan
Roan can also appear on any other base color or mixture of colors, so there are also buckskin roans, silver dapple roans, and so on. However, with dilution gene coat colors, the white hairs may not be as noticable.
Varnish roan coloring seen in the Appaloosa is not caused by the roan gene, but is the result of the varnish roan gene combined with the leopard (lp) gene that creates the distinctive spotting patterns of the breed.
[edit] Lethal Roan Question
There was a theory that a homozygous roan (RR) could be a lethal gene. This idea of "Lethal Roan Syndrome" was based primarily on a 1979 study.[2] This study examined the percentages of roan foals thrown by roan parents, and found fewer than expected. The study did not include direct genetic analysis, as such technology was not available at the time. Not finding large numbers of dead foals, the researchers concluded that any homozygous roan fetus was absorbed, thus preventing birth. This study and its conclusions popularized the idea of Lethal Roan Syndrome. This was consistent with the "dominant white" and "lethal white" studies available at the time; later study has shown that the dominant white or "W" gene in horses is lethal when homozygous (see White (horse), and there is a different, unrelated recessive condition called lethal white syndrome. Nonetheless, in the late 1970s, genetic science had not yet developed to provide a clear answer to the roan question.
A more recent genetic study of roans by Dr. Ann Bowling [3] refuted the lethal roan theory. Using modern genetic analysis techniques, Dr. Bowling found several homozygous roans and no evidence of a Lethal Roan Syndrome.
[edit] Roan in Dogs
The roan gene in dogs acts as a simple dominant gene. The action of the gene results in a mingling of colored and white hairs. To be roan a dog must have white areas; a solid colored dog can not be roan. Breeds where the roan gene commonly occurs are English Cocker Spaniels, English Setters, Australian Cattle Dogs, and German Shorthaired Pointers. The roan pattern also occurs in American Cocker Spaniels, Field Spaniels and Border Collies.
Roan dogs are more prone to deafness due to the absence of pigment during ear formation. There are no other health issues associated with this gene.
Black and white roans are referred to as "blue roans" (spaniels) or "blue belton" (English Setters). Red/buff and white roans are referred to as "red roans" "orange roans" or "lemon roans" or oran. Brown and white are referred to as "liver roans", "chocolate roans" or "brown roans".
[edit] Roan Cattle
The roan colour can also result in Shorthorn Cattle, but in a case of intermediate inheritance or Codominance. These cattle can not breed true, as this type of intermediate inheritance is also Heterozygous, or hybrid, as two different colour alleles are required form the parents to produce this particular coat colouring.
[edit] References
- ^ AQHA General Glossary
- ^ Hintz, H.F. and VanVleck, L.D., published 1979. Lethal Dominant Roan in Horses. Journal of Heredity 70:145-146.
- ^ http://www.hancockhorses.com/article-roanQHNews.pdf QH News
- Bowling, Ann T. "Coat Color Genetics: Positive Horse Identification" from Veterinary Genetics Laboratory, School of Veterinary Medicine, University of California, Davis. Web site accessed February 9, 2007
[edit] See also
[edit] External links
Horses
- Photo of blue roan
- Photo of grulla roan
- Photo of chestnut roan
- Photo of smoky black roan (black + 1 creme gene + roan)
- Photo of palomino roan
- Photo of silver dapple roan
- Photo of strawberry roan
- Photo of bay roan
- Horse Coat Color Genetics (Including roan definition, photos, and genetic formulas)
- Blue Roan Genetics and Photos
Dogs