roan (color)

Roan is a coat color found in many animals, including horses, cattle, antelope, cat and dogs. It is defined generally as an even mixture of white and pigmented hairs that do not "gray out" or fade as the animal ages."''roan'', ''a''. and ''n.1''" Oxford English Dictionary. 2nd edition 1989. OED Online. Oxford University Press. 3 June 2008. . There are a variety of genetic conditions which produce the colors described as "roan" in various species.

Roan horses

A horse with intermixed white and colored hairs of any color is usually called a roan. However, such mixtures, which can appear superficially similar, are caused by a number of separate genetic factors. Identifiable types of roans include true or classic roan, varnish roan, and rabicano, though other currently unknown factors may be responsible for ambiguous "roaning." Gray horses, which become lighter as they age until their hair coat is nearly completely white, may be confused with roans when they are young. Duns, which are solid-colored horses affected by the dun dilution factor on their bodies but with darker points, are also sometimes confused with roans, but they do not have the intermixed white and colored hairs of a roan.

Horses with the classic or true roan pattern may be any base color which is intermingled with unpigmented white hairs on the body. Except for white markings under the control of other genes, the head, mane, tail, and lower legs are dark. Roan is a simple dominant trait symbolized by the ''Rn'' allele. The University of California, Davis School of Veterinary Medicine's genetics services have developed a DNA test that uses genetic markers to indirectly determine the number of ''Rn'' or ''rn'' alleles a horse has. The mutation responsible for true roan has not yet been identified exactly, but been assigned to equine chromosome 21 (ECA21) in the KIT sequence. The overall effect is that of a silver or lightened appearance to the affected part of the coat.
Descriptions of roan coat colors are as follows:
* Red Roan or strawberry roan describes true or classic roan on a chestnut base coat. The mane and tail remain red or have only a few white hairs, while the body ranges from nearly chestnut to pinkish. Geneticists prefer the term "chestnut roan," but this term is not in common use.
* Bay Roan is true roan on a bay coat. The particular shade depends on the underlying shade of bay; but the mane, tail, and lower legs are black, and the reddish body is intermingled with white hairs. The head is usually red. Formerly, bay roans were lumped together with chestnut roans and both called "red roans."
* Blue Roan is true roan on a black coat. The mane, tail, head, and legs remain black, while the body takes on a grayish or bluish appearance. Blue roans are sometimes mistaken for grays or grullos. However, Grays fade with age, while roans do not; and grullos are blue duns and possess dun markings but not intermingled white hairs.

Any other coat color may also be affected by roaning. Few combinations have the same unique terminology applied to the common roan colors, although palomino roans are sometimes called ''honey roans''.

Roan mimics

A varnish roan is not a true roan; it is actually one of the leopard complex coat patterns associated with Appaloosa, Knabstrupper, Noriker horse and related breeds. Rabicano is a white pattern that falls into the category of ''roaning'' or scattered white hairs, the genetics of which are not yet fully understood. Sometimes called ''ticking'', rabicano is common even in breeds that do not have true or classic roan, including Arabians and Thoroughbreds. This pattern usually takes the form of scattered white hairs around the junction of the stifle and flank, and peculiar rings of white hairs near the base of the tail. This trait is called a ''coon tail'' or ''skunk tail''. Some forms of sabino, which is a pinto pattern, have roaning along the edges of other white spots or markings A roan horse may not fit into any of the traditional categories as there is much still to be learned about the genetics of roan. The existence of other types of roaning conditions not covered by those mentioned here is possible and likely.

Roan dogs

The genetics behind roan dogs are still unclear, and at present candidate genes have been ruled out. There remains a great deal of ambiguity in terminology regarding mottled dogs, which are called ''roan'', ''ticked'', ''mottled'' and ''belton'' depending on the context. The roan or ticked color is described in many breeds of gundogs such as English Cocker Spaniels, American Cocker Spaniels, English Springer Spaniels, Field Spaniels and Brittanys, German Longhaired Pointers, German Shorthaired Pointers, Bracchi Italiani, Spinoni Italiani, Lagotti Romagnoli, English Setters, Small Münsterländer as well as Border Collies and many other breeds.

In dogs, roan manifests itself only in unpigmented areas, the presence and shape of which are determined by other genes. This is in stark contrast to true roan horses and roan cattle, which are roan only in pigmented regions of their coat and may have white markings. Instead, dogs with roaning or ticking are born with clear, open white markings which begin to fill in with flecking in the subsequent weeks and continue to darken with age. Most breed standards use the terms "ticked" and "roan" interchangeably, with the former referring to clearly defined flecks on a white background and the latter to flecks so closely spaced that the mixture appears even.

The terminology that relates the underlying coat color with the roan modifier is often breed-specific, but most standards call a black dog with roaning ''blue''. In breeds that are characterized by roaning and ticking such as the Large Munsterlander, clear white-marked individuals may be called ''plated''. The term ''belton'' is reserved for English Setters.

In 1957, Little suggested that roan and ticking were controlled separately, and postulated that roan may have been homologous to "silvered" coat in mice. This condition in mice is actually homologous to merle, which might be described by some as "roan." In 2007, the gene responsible for roan cattle (KITLG) was refuted as a possible cause of roan in dogs. Ne