Roan (color) - Roan Horses

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.