ROAN is a dominant allele which modifies the coat colour by 'roaning' the body but leaving the head and legs the solid base colour. When branded or blemished the brand or blemish will grow back in the same solid colour as the head. A characteristic of roans is the spearing of the points on the front legs, in a non-roan the points end in the horizontal plane while in a roan they spear upward into the forearm. Often this spearing of the points is the only way to distinguish a palomino or buckskin roan.
Roan will work over every colour, the darker the base colour is the more distinct the contrast. Palomino & buckskin roans can be very hard to distinguish. Cremello or perlino roans cannot be determined on visual inspection, only by DNA zygosity testing or by the progeny they produce.
For many years it was believed that roan was lethal in the homozygous state ie if two roans were bred together that there was a 25% chance of a non-viable embryo which would be aborted. This has been disproved and genetic homozygous roans have been confirmed both in USA & Australia.
A DNA roan zygosity test has now been developed in USA which will make determination of dilute and double dilute roans a much easier task. This test was developed on Quarter Horses and Paints but has now been proven to work on Welsh, Ponies, Partbred Arabians, Riding Ponies & Australian Ponies so the test is now available at a low cost commercially. For further information see http://www.vgl.ucdavis.edu/services/Roan.php and http://www.vgl.ucdavis.edu/services/horse.php
A grey horse can carry the roan allele and produce roan foals if it was born roan itself. While a grey horse becomes progressively lighter with age, eventually ending up white, a roan horse is obviously roan at first coat change as a foal and will remain that colour forever. The body coat colour will lighten and darken according to the time of year but the head and points remain the base colour. Many horses which are turning grey are incorrectly termed roan as are many that are merely heavily ticked.
Left is a buckskin roan showing the characteristic spearing up the forearm.
Right is a non-roan buckskin showing the black point ending in the horizontal plane
Brands can be clearly seen on this chestnut roan & black roan
Palomino Roan Wesh Mountain Pony
Bay Roan Quarter Horse (above) & Australian Pony (below)
photo B Zaiter (Birdwood Rupert Bear)