Equine Colour Genetics
White Roaning Patterns

Rabicano is a White Ticking Pattern, generally accepted to be a Polygenic Incomplete Recessive Gene.
The predominant manifestation of the Rabicano coat pattern is concentrated areas of white ticking that originates at the flank area and radiates out over the body. Rabicano can manifest in as little white ticking as restricted to only the flank region in conjunction with white ticking at the tail head region, right through to covering the entire body including the head and legs [though this latter expression is comparatively rare].
Rabicano is one of the few equine colours that has never been the subject of official genetic research. As a result while there are an abundant number of theories as to the genetic cause and control of the Rabicano pattern, none of which have yet been officially acredited. As such, the information contained on this page, and throughout this website, on the Rabicano Gene contains theorized information gathered from various sources over many years.

Rabicano
©CHETAR ARABIANS 2006 - 2010
Website Designed & Maintained By Kielee Hawtin
Introduction
The Rabicano Gene
All Rabicanos MUST possess the Rabicano Primary Coat Markers


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Identification of the Rabicano Gene
The Rabicano Gene is one of three genes that are recognized for producing various patterns of white ticking as the predominant marking manifestation.
The Rabicano Gene, however, does have specific characteristics recognized as being cause by only the Rabicano Gene that set it apart from the other white ticking patterns and so the Rabicano Gene is generally one of the easiest to identify.
Rabicano is known as the "White Ticking Pattern" is some parts of the globe, especially the UK.
The name "Rabicano" is a Spanish derived term used exclusively for this pattern in many parts of the world.

Throughout this site I have used the terms Primary Coat Markers and Secondary Coat Markers in an effort to simplify the task of identifying the individual genes and resulting patterns caused by them. Primary Coat Markers are the markings and/or characteristics that a horse MUST POSSESS to be classified as carrying a specific gene, while Secondary Coat Markers are the markings & characteristics that a horse MAY or MAY NOT possess, that are used to further classify the degree of pattern expression caused by the specific gene. Furthermore, I have outlined the various markings attributed to individual genes individually, and split them into two groups - The frist identifies the markings that are attributed to being caused by a single, specific gene alone, and the second group identifies the markings that could result from that specific gene but are also attributed characteristics of another gene as well.
The TERMINOLOGY PAGE contains full explanations of the more uncommon and/or technical terms I've used throughout this site.


Primary Rabicano Coat Markers
White Ticking at Tail Head + White Ticking in Flank Region

There are two Primary Coat Markers for the Rabicano Gene. While there are a variety of white ticking pattern characteristics attributed to the Rabicano Gene, the two Primary Coat Markers will be present regardless of the other additional, if any, markings the horse possesses if it is indeed a Rabicano.
These two Rabicano Primary Coat Markers are White Ticking at the Tail Head/Dock Area in conjunction with White Ticking at the Flank Region.
For a horse to be identified as having the Rabicano Coat Pattern, it must possess both of these two Primary Coat Markers.
It should be noted that, while the white ticking at the tail head/dock area in conjunction with white ticking in the flank region, are the two absolute indicators for the Rabicano Gene, and that they will always be phenotypically present in those individuals who carry the genotype for Rabicano, the white ticking may be that minimal as to be easily missed as being present, let alone attributed to a colour gene. There may also be extensive white ticking elsewhere on the body, with only very minimal white ticking in the noted regions as to result in the misidentification of the causative gene. The Primary Coat Markers of the Rabicano Gene may manifest in as little as only a few hairs at both the tail head/dock area and at the flank region. If the horse is Rabicano though, there will be at least a couple of white hairs in these regions - They are the absolute indicators for the Rabicano Gene.

Secondary Rabicano Coat Markers
Classification of Rabicano Expressions
Minimal Rabicanos express only the two Primary Coat Markers. As little as a few white hairs intermingled with the base colour at the flank in conjunction with the tail head, through to an easily visible, though not intensive, patterning of white ticking at these areas are classified as Minimal Rabicanos.
A Minimal Rabicano at the higher end of the classification will have easily visible white ticking at the flank and tail head, but it will be limited to these areas, the background colour of the horse will still be easily seen between the pattern of white, and they will not express any of the Secondary Coat Markers.
Common Rabicano Misconceptions

Rabicano is often confused with the Roan Gene, one of two other genes responsible for various White Ticking pattern manifestations that is present in almost all horse breeds. The Roan Gene is not, however, present in the Arabian breed. To confuse the separate genes further, Rabicano is often termed Arab Roan as it is one of only two white pattern expressions presently identified in the Arabian breed [the other being the Sabino Overo Gene]. To simplify the confusion this can cause, all references throughout this site to "True Roan" refer to the Roan Gene and the pattern manifested by it.

The white ticking caused by the True Roan Gene manifests in a visibly different pattern than Rabicano. It is usually easily distinguished from Rabicano when you know what to look for. The True Roan Gene results in a consistently even coverage of white ticking over the entire abdomen and neck of the horse. The entire head, from the throat latch to poll and forward, always remains the base/modified base, or background, colour of the horse - with no white ticking whatsoever on the head. In most cases, this same True Roan trait of remaining the background colour applies to the lower legs of all Roans. As such, the easiest way to differentiate between the Rabicano and Roan Genes is to assess the head of the horse. White hairs present forward of the throat latch automatically rule out the Roan Gene and confirm the presence of another gene, which may in fact be Rabicano - Baring in mind that Rabicano is not the only white ticking pattern that results in the appearance of white hairs on the head, and as white ticking on the head is not a prerequisite marking [Primaru Coat Marker] for the Rabicano Gene either, further evaluation would be required to identify whether the white ticking is caused by Rabicano &/or Sabino Overo.

The other reliable method of distinguishing between the True Roan and Rabicano Genes can be to assess the body. The Roan Gene is a Complete Dominant Gene - Irrespective of whether it is heterozygous or homozygous, the pattern it manifests is identical. The Roan Gene causes white ticking that covers the entire abdomen and neck , there is no limitation to certain areas of the body as with the Rabicano manifested pattern. The only time white ticking covers the entire body with Rabicano is with a small number of Maximum Rabicanos, and in these cases the white ticking will [hardly] never be uniform in coverage, and they will always have further definitive Rabicano indicators such as the coin sized patches, rib barring and/or extreme white ticking concentrations.

Genetic Control of the Rabicano Gene

As Rabicano has never been the subject of formal studies, the controlling loci and recessive vs dominant vs wild alleleic combinations present at the gene are still unknown, so the following abbreviations are really just 'guesses' by those in the know at the genetic control and the alleles that lie there are.
Rabicano is represented by the locus abbreviation [Rb].
A horse that does not carry Rabicano is [RbnrRbnr] at the Rabicano Locus.
Non Rabicano/Homozygous Recessive = [RbnrRbnr]
Heterozygous Rabicano = [Rb+Rbnr]
Homozygous Rabicano = [Rb+Rb+]

Note: With the true genetic mechanisms of Rabicano being questionable, a horse being Homozygous for Rabicano remains unable to be absolutely confirmed and so horses possibly homozygous at the Rabicano Locus should have the genotype representation of [Rb+Rb-].


 

Genes & Markings Linked to the Rabicano Gene

There is evidence that the Rabicano Gene is linked to the Sabino Overo Gene. It is quite common for a Rabicano to express Sabino Overo, and many people make the common mistake of assuming their Sabino Overo horse is actually a Rabicano [Rabicano does not involve white facial and leg markings at all, while facial and leg white is a prerequisite - are Primary Coat Marker - for Sabino Overo Gene]. In addition, a true Rabicano [without Sabino Overo in addition to it], that carries a Moderate or Maximum expression is even more highly unusual. All of which gives evidence to the following theory.
It is theorized that the Sabino Overo Gene acts as a type of support for the Rabicano Gene. Essentially the Sabino Overo Gene's genetic mechanisms [remembering that it is also a Polygenic Recessive Gene] effectively 'strengthen' the genetic environment required for expression of the Rabicano Gene, resulting in a stronger phenotypical manifestation of Rabicano [alongside Sabino Overo]. Both genes are Polygenic and share an expression characteristic [ie. White Ticking], so it is highly possible that both genes share a number of genetic environmental factors that must be present for the phenotypical expression. It is also theorized that Rabicano may possibly also strengthen the Sabino Overo Gene as well, resulting in a more intense expression of Sabino Overo as well.

Moderate Rabicanos express both of the Primary Coat Markers in high concentrations, along with one or two of the Secondary Coat Markers. The Secondary Coat Markers will be easily seen, and can occur in any combination in conjunction with the Primary Coat Markers [but will be limited in number & intensity].
Maximum Rabicanos express all of the Coat Markers described above - both the two Primaries as well as all of the Secondary Coat Markers.
Minimal Rabicano
Moderate Rabicano
Maximum Rabicano
The appearance of creamy to white hairs down the backs of the legs, on the belly and on the throatlatch and under the jaw, is also a trait seen in some Rabicanos. The hairs may be completely white or may be white 'tipped' with the remainder of the hair shaft the background colour of the horse.
Generally termed Frosting, less is known about this trait, but it seems to occur in all three expressions of the gene, though without much consistency. There is a coat pattern that has also been named Frosting that manifests exclusively in the frosting traits I've mentioned here. Theories surrounding this pattern/trait suggest it may indeed be a Rabicano mutation, a pattern linked to the Rabicano Gene, or a subtype pattern expression, possibly a partial mutation, of the Rabicano Gene itself, with much of the evidence to date supporting this latter theory above the rest.
[See the final sections on this page for more information on the Rabicano Gene theories].
Specific Areas of White Ticking
White hairs appear in the mane and/or tail of some Rabicanos. This trait is termed Mane and/or Tail Frosting, and is most commonly seen in Maximum Rabicanos, though can sometimes appear with the other Rabicano expressions. The mane and tail frosting can be that intense that the mane and/or tail are completely white/silver in colour, or may be as little as just a few white hairs - or anything in between.
There is some evidence supporting the theory that a Rabicano Gene mutation is the cause of the colour phenomonen where a horse will have a white/silver mane and/or tail with an otherwise complete lack of any other modification of colour, as well as a complete lack of indications of another colour gene in play.
Mane & Tail Frosting
Small solid spots of white appear under the tail and between the hind legs of some Rabicanos. They differ to the above mentioned white ticking spots [coin sized patches of extreme concentrations] in that they can appear on any Rabicano expression and are solid patches rather than intensely ticked- They are irregular in shape, come in a small range of sizes, and can also be disconnected in some cases [as aposed to being circular in shape and coin sized in appearance as with the maximum expression patches described above]. They are, however, generally smaller than a five cent piece in most circumstances.
Small Solid White Patches in Specific Areas
The most common secondary marker of the Rabicano gene is intense concentrations of White Ticking appearing in the localized areas of the flank, belly, barrel, under the jaw/along jawline, at the throatlatch and between the fore and hind legs. This Rabicano White Ticking trait is seen in all degrees of expression - Minimal, Moderate and Maximum Rabicanos - though to largely varying degrees. It is generally widely accepted that the more intense the concentrations of white ticking, the more intense the degree of expression.

Coin sized patches of extreme concentrations, so intense they [can] seem to be solid, appear under and tail and between the hindlegs, and sometimes also within the ticked areas of the flank and belly regions. This patching trait is usually reserved for Maximum Rabicanos. This trait is also theorized to be an indication of homozygosity, much the same as paw prints/cat tracks being a trait proven to indicate Homozygosity in Tobianos.
Extreme Concentrations of White Ticking
Skunk Tail
It is a common misconception that a Rabicano must possess the Skunk Tail trait in order to be classified as a Rabicano - A horse does not have to have a Skunk Tail to be a Rabicano. This is the most commonly held misconception applying to Rabicano. For a horse to be Rabicano, the prerequisite is white ticking at the flank in conjunction with white ticking at the tail head - Not white ticking at the flank and a Skunk Tail as commonly believed.
A Maximum Rabicano [a horse carrying the most intensive expression of the gene] will almost always have extensive white at the tail head and in the tail - Either a Skunk Tail and/or intensive tail frosting, but a Minimal Rabicano [the least expressive] will commonly have very few white hairs at the tail head. Just a few white hairs at the tail head along with a few white hairs at the flank can be indicative of the presence of the Rabicano Gene.
Rabicano vs True Roan
Gene: Sabino Overo
Lacing is considered to be one of the few true phenomenons of horse colour genetics. It is one of, if not the, rarest occurences you will find. Adding to this is the fact that many of those that own horses with lacing assume that the pattern is the result of a previous injury, illness or coat condition and so never think to actually research what is in fact a colour characteristic! I have heard everything from wire fence injuries through to being 'left over' from Queensland Itch and rain scald being attributed to having caused this patterning on horses! All of these horses were/are in fact horses with the Lacing White Pattern!
Lacing causes the appearance of white hairs along the topline between the wither and tail head. The white hairs form a cobwebbed type of pattern that gives the horse a highly unusual look. Adding to the confusion of this pattern being caused by previous injury etc is the fact that Lacing is a developed pattern, not something that appears at birth or upon the foal coat shedding. The most common age of development is between the ages of 4 and 6 where the white hairs will begin to grow, forming small spots along the topline and progressively 'joining' into the Lacing pattern.
The evidence that supports Lacing being linked to the Rabicano Gene is abundant. Many horses develop associated Rabicano markings at the same time that the Lacing begins to appear, where they have previously had no indicators for the Rabicano Gene. Lacing also develops on true and combination white pattern Rabicanos later in life. Horses that develop the Lacing pattern alone are also commonly of Rabicano breeding. All of which supports the theory of this unusual, rare pattern being linked to the Rabicano Gene.


Marking: Lacing
The White Pattern "Frosting", or "Frosted", has long been considered by many to be an a separate white pattern. Recently there has been growing support for the theory that the pattern known as Frosting is actually a manifestation of the Rabicano Gene. There is much more evidence to support this theory than there is that indicates Frosting to be a completely separate gene.
The formal description of the Frosted pattern is highly similar to that of Rabicano. It is said to cause uneven white ticking body markings, including on the head, along with white hairs in the mane and tail, and white 'tipped' guard like hairs on the body and more intensively on the belly and legs.
Interestingly enough, Frosting and Frosted is commonly used in describing the coat markings resulting from the Rabicano expression.
Marking: Frosting/Frosted
Rabicano vs Sabino Overo
Rabicano is also often confused with the Sabino Overo Gene, which is the only other gene besides Rabicano & True Roan that is a recognized White Ticking characteristic producer. The Sabino Overo Gene results in white ticking that can appear anywhere on the body, and in the areas that it does appear, the white ticking is uniform across the affected area. The Rabicano Gene white ticking manifests in restricted areas only [see the Primary & Secondary Coat Markers above for more information on these], and the white ticking appears in a highly irregular pattern - it is not uniform. The differences noted here between the white ticking manifestations is the easiet way to differentiate between Rabicano & Sabino Overo. As Sabino Overo also causes white ticking in unrestricted areas of the body, the same body assessment used to differentiate between Rabicano & True Roan [see above] can be used in regards to Sabino Overo as well.


Rabicano Combination Genes
Rabicano in Combination With Other Genes
The Rabicano Gene can appear in conjunction with any white pattern as well as on any background colour.
The most common combination is of Rabicano appearing with Sabino Overo, and it is in fact theorized that these two genes may be linked [see Genes & Markings Linked to the Rabicano Gene below]. When the two of these genes appear together, the result can be quite striking, with the horse usually displaying generous amounts of white, with both solid white markings as well as white ticking. Rabicano and Sabino Overo are most commonly seen together when both are in their minimal expressions, with these still amounting to quite a lot of white. There are a number of individuals with moderate to maximum expressions of both genes, though this is considered rarer than the minimal expression combination.


Rabicano Marking Characteristics
White Ticking Characteristics
The white ticking that manifests as a result of the Rabicano Gene is highly irregular and localized. All bar only a few of the most Maximum of Rabicano Expressions will have white ticking that is localized/restricted to the abdomen [barrel, belly and flank regions] only, with no white ticking forward of the wither to chest on the body. Those Maximum Rabicanos that do have white ticking forward of the line from wither to chest on the body will display a pattern of highly irregular white ticking - The white ticking will be intense in some areas, but not in others, with no 'eveness' to the patterning at all. This characteristic is useful in identifying Rabicano as the two other genes that manifest in white ticking are characterized by even patterns of white ticking.
Barrel Barring
Small Spots of Intense White Ticking
Skunk Tail
Skunk Tails, also known as a Coon Tail in some localities, is the term given to those Rabicanos that display extremely intensive areas of white ticking at the tail head/dock area. This trait is characteristic specific and appears only on the more intense degrees of Rabicano expressed individuals, and is generally a trait reserved as an identifier for the Maximum Rabicano Expression only. The extremely intense areas of white ticking appearing at the dock area manifest in a 'striped' pattern that forms one or more horizontal [when the horse is viewed from the rear] "bars" across the tail head and/or region/s. This trait is unique to the Rabicano Gene, and is named for its' similarity to the striped pattern seen on Skunks' and Racoons' tails.


Frosted Rabicanos
This term is not yet an official classification for the Rabicano Gene but it is gaining in popularity and will likely soon be used across the board to describe those individuals that express the pattern traits of Mane &/or Tail Frosting &/or Leg Frosting [as described above in Secondary Coat Markers].


The term Barrel Barring, also known as Rib Barring in various localities, is the name given to the Rabicano trait that results in the manifestation of white ticking in a pattern of vertical stripes, or vertical bars as the name suggests, along the sides of the barrel, or along the ribcage area to be more precise.
The vertical barring is not the same as the Skunk Tail trait in that the Skunk Tail trait is a manifestation of white ticking so intense that the horizontal bars appear to be solid white, whereas the barrel barring trait is a less intense arrangement of white ticking that appears to form a pattern of bars, most easily seen from a distance and not easily discerned when up close to the horse. When viewed up close there appears to be no rhyme or rule to the patternwork of white ticking, with only a few individuals possessing this trait in its' most intensive, easily seen from close to the horse, form.
The final marking characteristic that is true to only Rabicano is the trait of white ticking spots. These spots vary in size, from around the size of a fifty cent price down to smaller than a five cent piece, but are always very similar in appearance. They are always circular, near on perfectly so, with no pointy or jagged edges to them at all, and they are always formed by white ticking. They usually appear to be solid, or nearly so, but upon closer inspection will reveal themselves to be tightly woven spots of intense white ticking and not solid at all. None of the other genes that manifest in white ticking cause this trait.


Rabicano Attributed Markings
White Ticking Over the Barrel & Abdomen - Sabino Overo & True Roan
Polygenic Recessive Gene

As I have previously mentioned, the Rabicano Gene has never been the subject of formal genetic studies, so the exact genetic mechanisms that control the expression have yet to be determined. The recent rise in popularity will likely see this change in the near future though - hopefully sooner rather than later!

Rabicano is somewhat similar to the Sabino Overo Gene in that some families appear to consistently pass the expression on to their progeny in what appears to be a dominant trait. On the flip side though, many families do not follow this trend, with the gene appearing to have a recessive mode of inheritance, with only the odd descendant phenotypically expressing the pattern [commonly termed Crop Outs]. In addition, True Crop outs have been shown to occur after many generations of seemingly non Rabicano carriers. These genetic behaviours subsequently support the theory that Rabicano [as with the Sabino Overo Gene] is a Recessive Gene. Rabicano [seems to] require a certain genetic environment, a certain combination of genes, in order for a phenotypical expression to be achieved, and so it is therefore thought to be a Polygenic Gene [controlled at multiple gene loci]. This is supported by selective breeding pattern results.

Genetic Shorthand: Rabicano
The following Rabicano Marking Characteristics are the traits that are accepted as being caused by ONLY the Rabicano Gene.
The following Rabicano Attributed Markings can result from NOT ONLY Rabicano, but also from other Colour Genes.
White Ticking is a proven pattern trait of [at least] two other white pattern genes, those being Sabino Overo and Rabicano. As such, it can be difficult at times to distinguish between the three and there are many commonplace mistakes made with the identification horses that carry one or more of these genes.
While they all can manifest in white ticking, each has its' own specific pattern of manifestation, and the differences in there is what is used to distinguish each pattern individually and in combination with eachother.
The more important rule to remember when trying to identify Rabicano as a white ticking pattern causative is that Rabicano results in areas of white ticking that are almost always restricted to the flank and dock/tail areas, and even when in its' most maximum of expressions where its' possible for a Rabicano to display more extensive white ticking in other areas of the body, there will always be a more intensive display of white ticking in these areas - There is nothing "even" about the Rabicano Gene and the pattern that results from it - Whereas, the other two commonly recognized white roaning causatives manifest in an even pattern of white hairs across the entire body including the head with Sabino Overo and across the entire body excluding the head with Roan.

The basic principles I use when first approaching the separate identification of these three patterns are the following two, very simple rules:
1) Does the horse have white ticking in areas other than the dock/tail and flank? If not, it is Rabicano. If so, it's not Rabicano; move on to step 2..
2) Does the horse have white ticking anywhere on its' head? If so [& it also have white facial & leg markings], it's Sabino Overo. If not, it's Roan.
It should be noted through, that the rules stated above are only the first steps to identifying each of the patterns in general and that further additional steps of assessment may need to be taken in some cases dependant upon the intensity of expressions, so above rules do not always apply in all cases.