Sunday, June 15, 2014

Rabicano and Roan: Two Unique Horse Color Patterns

Several years ago, my palomino mare, Hollywood Royal Lady (Holly), foaled a gorgeous bay stud colt who grew up to be my current stud horse, MJ Royal Smartypants (Ziggy). Ziggy was clearly a bay, but he had a unique "mealy" color -- meaning that he had subtle fawn coloring on the sides of his muzzle, along his ventral midline, and around his groin.  As his silky baby coat shed out and the mealy coloration dissipated, I could see distinct white hairs here and there.  They weren't in solid white patches, like a pinto, but were intermingled with the red of his bay coat, with some congregating together heavily.

Now, I've always loved roan horses and, never having had my name on a roan's papers, was hopeful Ziggy would magically mature into a bay roan.  Bay roans, for those who aren't up on roan genetics, are bay horses with a roan gene that is sole and separate from the base color of the horse.  Ziggy doesn't have that roan gene after all -- which a horse must inherit from one parent.  Instead, he has what is called a "rabicano" variation.

Rabicano!  What a great name.  It sounds wild and western.  It's a Spanish word that means "brush-tail." (How romantic is that?)  Rabicanos, as you might figure from that "brush-tail" translation, also have white hairs at the tail's base. They generally have white on the flanks and often on the barrel.  Ziggy's mother, who is a golden palomino, also has the rabicano trait; she has a couple of different good-sized areas where the white hairs predominate on her hip and neck.
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Holly's dock area, showing rabicano as expressed in the palomino color.

The rabicano color trait is commonly known as "ticking."  Consider a blue-tick hound, or an Australian cattle dog; they're excellent examples of that ticking trait.  However, many people aren't aware of the rabicano variation and will misidentify a horse as being a roan or a grey when it lacks the genetics to be either roan or grey.

If you're unsure about whether your horse is a roan or a rabicano, here's the sure-fire way to tell:  a roan will always get darker where hair has been rubbed off.  For example, if the horse has worn a fly mask, they'll often have the darker burnish on the lower front of the face where the bottom of the mask has rubbed.  You may be familiar with roans that have dark lines or marks across their body.  Those areas show the original base color of the roan; scratch a roan, you get that base color back, and only that base color.  However, if you scratch a rabicano that has no roan genes, you get white hairs.  A rabicano will respond like a solid-color horse:  with white re-growth.
Note the white hair above Ziggy's tail as well as interspersed randomly throughout his rump hairs.

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Close-up of typical rabicano white hair cluster.

Just about any color or color-patterned horse can be a rabicano.  Thanks to Holly's genes, here on the property we have rabicano in sorrel, palomino, and bay.  Each of them has very clear ticking and loosely-clustered hairs forming white patches.

Now, a few words about roans.  A roan has the same genetics of solid-color horses, but with the addition of a roan gene.  As mentioned above, that gene must come from one parent or the other -- even if the parent horse doesn't express the roan color, they still carry the roan gene.  A bay roan is said to be a bay that "expresses" the roan gene.  A bay horse can carry a roan gene but not pass it on to its foal, in which case the baby horse carries the gene but does not express it.  Confused yet?  Think about this:  a bay horse is genetically a black horse that has an agouti gene (making it a bay); a bay roan is a bay horse that expresses a roan gene.

A strawberry or red roan is a sorrel or chestnut, genetically, but it carries and expresses the roan gene.  A blue roan is a black horse that carries and expresses the roan gene -- but it does not have the agouti gene that would otherwise turn it into a bay horse.  Not all horses referred to as "blue roan" are true blue roans, though:  some are actually grullo horses with a roan gene.

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Here's a bay roan bucking horse.

A buckskin can also express a roan gene, if it has one parent that carries that gene and if the other parent is a cream dilution.  (I won't get into the dilute genes in this post.)  You'll never see "buckskin roan" on AQHA papers, though; they're simply registered as "buckskin" with the possible addendum, "Carries and expresses the roan gene."

For the newcomer to the study of horse color, it's important to understand that color and pattern are two different concepts, and they're often misapplied.  Horses have a base color which is affected by genes for various patterns and effects, so to speak.  A horse may have the base color for black, but carry the pinto gene so that they have a color pattern of pinto.  Perhaps an easier example is an Appaloosa:  a black horse may have the genes that cause spots on the rump.  The color is black; the pattern, Appaloosa or spotted.  It can be confusing unless one keeps in mind that all horses have a base color plus the effects of various patterns.

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