Stable Minds - For Equine Enthusiasts

Genetics of the Blue Roan Color
A Medium-level Description for Novice Genetics Readers
by Toni Perdew
Reprint of an article originally published on http://www.grullablue.com

This will not be a technical description, but will be intended more for the person with a medium interest in learning about the blue roan coat color (a beginner or person early in the learning stage).

The blue roan color is a rare color (and difficult to breed for) because the conditions must be "just right" or else you get another color of foal. In order to have a blue roan foal, you need to have a foal with:

black legs,

a genetically black body, and

roaning.

There are some pretty basic factors/alleles (we'll call them genes, but that's not quite always correct) that mainly control this:

Red Factor

Agouti

Roan

Before beginning, we need to lay some ground rules to simplify this as much as possible. For this simplification:

We are not discussing the effects of the gray gene (or many others) on these base colors, so for now, just ignore those. See the bottom of the page for the way to tell roans from grays.
The color "red" also includes yellow as in palomino or dun or buckskin.
The term "body" includes the barrel, hip, head, and neck, but not the legs, mane, and tail.
Each gene for a trait consists of a pair of alleles, with one coming from the sire and one coming from the dam.
We are ignoring a lot of other stuff that will clutter this explanation up, and that would make it harder to understand.

The First Oversimplification

Remember that I am going to oversimplify on this whole page in an attempt to make this a quick and easy thing to understand, and that this whole page is arranged according to how my own deranged mind works. :-) If you go on to read about color genetics, you'll realize here that some things (mainly vocabulary) aren't quite correct or are very oversimplified, but my goal wasn't to be 100% correct--it was to water down the genetics info to make it easier to understand. This page will actually help you understand genetics and help make you ready to go to that next level (that page is coming soon). Here are my first oversimplifications!

	The color of the horse's legs is controlled by the E and e locus alleles (we'll call it a gene, though that's not quite correct). E is for black legs, and e is for red legs. One E will override any e, so any horse with an E (capital letter) will have black legs.
	The color of the horse's body is controlled by the A and a locus. An A means red body, and an a means that the body will match the legs in color. The A is dominant, so any horse with an A will have a red-based body.
	The roaning is controlled by the R and r alleles. Any horse with a R will be a shade of roan, where a horse that is rr (no capital R's) will not have roaning.

Red Factor

The answer to the question, "Why are his legs red or black?"

Since grullas have black legs, we know that they must carry at least one black (non-red) gene. To correctly represent this, we really need to say that they should not carry two red genes, but instead should carry one or two non-red (black) genes. The black color is dominant over the red color, and is represented by the capital letter E. The red color is represented by the small letter e.

So, in regard to the red genes, there are three possibilities:

	ee, which is a red-bodied horse with red legs
	Ee, which is a black-legged horse. The body color depends upon the Agouti locus (below). This horse's foals can have either red or black legs.
	EE, which is a black-legged horse that will always throw black-legged foals (this horse is commonly referred to as homozygous black)

Therefore, any horse with black legs must have one "E" or two "E" genes, and would be either Ee or EE. A red horse would be ee here. See http://www.vgl.ucdavis.edu/horse/redtest.html for more details, and information about testing for red factor.

Agouti

The answer to the question, "Why is his body red or black?"

The Agouti gene is a dominant gene, and if it is present in a foal, the foal can NOT be blue roan (or black, or grulla). The Agouti gene mainly affects the color of the body, but not the legs, mane, or tail. A sorrel horse can have one or two Agouti genes, as can a bay (their bodies are red). But a black, grullo, or blue roan horse cannot have any Agouti genes, because they have black-based bodies. This is why blacks, grullos, and blue roans are so hard to get, and therefore are considered a recessive color. The capital letter A represents the red body caused by the Agouti gene, while the small letter a represents the lack of the Agouti gene (which allows for black bodies). Agouti possibilities are:

	aa, which is a horse with a body color that matches its points (legs, mane, tail). There is no Agouti gene causing the body to be red. The body can be either red or black, depending upon the red/black genes (e and E) discussed above.
	Aa, which is a horse whose body will always be red (never black). This horse can pass along the Agouti (A) gene, but won't always.
	AA, which is a horse whose body will always be red (never black). This horse will ALWAYS pass along an Agouti gene to its foals, and therefore will never, ever have a true black, blue roan, or grullo foal.

To put those two together (red/black and Agouti), you can get the following combinations:

Base Color	Red/Black	Agouti	Genotypes
Red colors (sorrel, palomino, etc.)	ee (no black hairs)	aa Aa, or AA (all with red legs and bodies bodies)	ee aa, ee Aa, or ee AA (all sorrel/chestnut)
Bay colors (bay, buckskin, dun, etc.)	Ee or EE	Aa or AA (black legs, red bodies)	Ee Aa, Ee AA, EE Aa, EE AA (all bay based)
Black colors (black, grullo, blue roan, etc.)	Ee or EE	aa (black legs, black bodies)	Ee aa, or EEaa (black based)

Another comment about Agouti genes: The only ways to know for sure if a horse carries the Agouti (red body) gene are to have foals from the horse that express the color (bay-based colors), to have that horse actually expressing the gene (black legs with red/yellow body), or to know the genetics of its parents. Many people think of the Agouti gene as being the "bay" gene, because it is what causes an otherwise black horse to be bay. In reality, the Agouti gene prevents blacks by turning them into bays. Keep in mind that sorrel/chestnut colors can carry the Agouti gene, even though they don't show it. Since their bodies are already red, you just can't tell they may carry the Agouti gene.

Roaning

The answer to the question, "Why does he have a mixture of white and dark hairs or else solid silvery-white hairs on his barrel, hips, neck, and shoulders?"

Now, the third gene/allele in the series: roan. This gene creates a body and hip that is a variation of white or white mixed with the head color. During the short-hair times of year (summer and adjoining seasons), roan horses will have dark heads (bay, sorrel, black) but bodies ranging from salt and pepper coloring to pearly to metallic white! The capital letter R represents roan, and the small letter r represents the lack of roaning.

The roan locus can be represented as follows (but is also known as Rn and rn):

	rr, or no roan markings
	Rr, or roan pattern present. This horse will pass along roan pattern to about half of his/her foals. At least one of this horse's parents was a roan horse.
	RR, or roan markings present. This horse will ALWAYS pass along roan markings to his/her foals. Both of this horse's parents must have carried and shown the roan gene. This type of horse is almost never, ever found because it is theorized that the fetus dies in-utero when it carries two roan genes. A few exceptions do reportedly exist, and there is controversy as to whether the RR embryo does die or not. With so very, very few homozygous roans known in existence, I would have to support the theory that homozygous roans are almost never born until definitive research shows that there is NO problem with homozygous roan embryos. See Equine Color Genetics by Dr. Phillip Sponenberg, 1996, p. 58 for more information.

To make the table more complete, we can now add roan:

Base Color	Red/Black	Agouti	Roan
Red colors (sorrel, palomino, etc.)	ee (no black hairs)	aa Aa, or AA (all with red legs and bodies bodies)	rr, Rr or RR
Bay colors (bay, buckskin, dun, etc.)	Ee or EE	Aa or AA (black legs, red bodies)	rr, Rr or RR
Black colors (black, grullo, blue roan, etc.)	Ee or EE	aa (black legs, black bodies)	rr, Rr or RR

Now, just put the pieces together. I generally look first for black legs, and then for body color, and then on and on to determine the best guess for a horse's genotype. It is a process of elimination, kind of. For example.....

If a horse is ee Aa rr, it will be a sorrel or chestnut. The ee means it is a red horse. Aa means it has a red body (A), and rr means it does not carry roan factor, so it isn't a strawberry roan, but rather is just a sorrel.

If a horse is ee AA Rr, it will be strawberry roan. The ee means it is a red horse. AA means it has a red body (A), and Rr means it does carry roan factor, so it is a roan instead of a sorrel.

Going in the other direction, if I see a horse that is strawberry roan, I know it is ee (because it has no black legs), and that it has at least one roan allele (because it has roaning). It is not possible to tell if it has an A, because the A only expresses itself visually when the horse has black legs and a red body. So, this horse is ee ?? R? for the placeholders of red factor, Agouti, and roan. The ? marks mean that I don't know what the horse has at that location in its genetic structure.

If a horse is Ee Aa rr, it is bay. E means black legs, so the Ee is a black-legged horse. Aa means red body, so this black-legged horse has a red body. The rr means no roan, so the horse does not become a roan...it stays a black-legged horse with a red body: a bay.

Going in the other direction, if I saw a bay horse, I'd be able to tell certain things about it. First, it has black legs so I know it has at least one E (but I don't know for sure if the other allele is e or E). Secondly, I know it has at least one A, because it has a red body with black legs, but I don't know if the other allele there is A or a. I also know it has no roaning, so it is rr. Therefore, I know that for those three traits, the horse is E? A? rr.

If the horse changes slightly, so that it is aa instead of Aa, then it does NOT have a red body. So if it is Ee aa rr, it would be black-legged (Ee), no red body (aa), and rr means no roan. It's a black-legged, black bodied horse...it's a black!

What if that same horse was a roan? It would be Ee aa Rr, so it would be black legged (Ee), no red body (aa), and have roaning (Rr). What is a black-legged horse with roaning that does not have a red body? A blue roan!

The next step is to figure out what the likelihood of your horse's foal's color will be, using the genetics of the mare and the stallion!

What is the Difference Between Roans and Grays?

Roan and gray are caused by two different genes. To tell the difference between the two, look at the head.

If the horse's head is darker than its body, it is probably a roan. Roans generally have a mane and tail that are solid and dark in color when compared to the color of the body.

If the head is lighter than the body, or if it is turning lighter every year, the horse is a gray. Grays that are mature will also have a mane and tail that is usually lightening up and turning gray.

Many roan breeders like to cross on gray mares, but I am concerned with that practice. They think the gray gene will accentuate the roan gene, but it doesn't...it covers it up! The result is that some people are buying foals that they think are roan, and that are being represented and priced as roan foals. But by the time the foal is 5 years old, it's just a plain old gray. While grays are also popular, if someone buys a roan because they like roan, they may be in for a major disappointment if that roan turns into a gray. My suggestion to you, as a buyer, is to be wary of buying a "roan" foal that has a "gray" parent. As a breeder, my hope is that you'll try to accurately represent foals resulting from roan to gray crosses, and even to educate the buyer so they are prepared in the event that the foal turns gray.

Roan. Note that the head/face is darker than the body. This horse will not turn white, and will always retain black legs, mane, tail, and head.
Gray. Note that the face is lighter than the body, and the tail is lightening. This horse will eventually become nearly white.

What are the Differences in the Shades of Roans?

This is a controversial issue! In my opinion, many people who have bay roans want to call them blue roans because the blue roans are more valuable and rare. But to me, if a horse is genetically a bay with roan, it is a RED roan and not a BLUE roan. Some disagree, but I represent it that way so that I'm not cheating anyone who is buying from me or breeding to my stallion--I believe in being honest about their horse or their future foal, and this is the safest and most honest way to represent the roan shades!

Strawberry Roan (also referred to as red roan)
AQHA calls these "Red Roans"
Red or Bay Roan (bay-based). Note the BAY face.
AQHA now allows these to be called "Bay Roans", though many people mistakenly call them Blue Roans.
Blue Roan (black-based). Note the BLACK face, and FEW or NO red hairs on the horse.

Note: AQHA changed its color rule in 2002 to allow for a distinction between sorrel-based roans and bay-based roans. Prior to this, both those colors were referred to as Red Roan.

What do roan foals look like?

This can vary a lot. Some foals are born with obvious roaning, and cannot be mistaken for roan foals from the beginning. Others are born with no obvious roaning, but shed off to become roan to the surprise of their owners.

To know for sure, one can only wait. But lifting the hairs on the hips and above the tail can provide early clues. If the underhair is white or silver, then the foal may roan. Below are a couple of pictures of roan foals with their foal coat and also after shedding. Roans generally show their roan coloring by a few months of age. Roans are not considered to intensify in roaning as they age. That is generally a characteristic of grays.

Coat

With foal coat color:

After shedding foal coat:

Foal #1

Looks bay, but....
What a color difference!

Foal #2

Born grullo...
Shed off grullo roan (blue roan variation)

Foal #3

Born bay
Shed off bay-based roan

Links

http://www.vgl.ucdavis.edu/~lvmillon/ University of CA Horse Genetics Page

http://www.vgl.ucdavis.edu/horse/redtest.html Red Factor Test Information

http://www.vgl.ucdavis.edu/horse/redfactr.htm Red Factor Test KIT for sending in samples to have your horses tested.

References

Knowledge gained over the years from books, articles, and acquaintances made vie e-mail.

Dr. Phillip Sponenberg, DVM, Ph D. Equine Color Genetics.

http://www.vgl.ucdavis.edu/~lvmillon/ University of CA Horse Genetics Page