|
THE (simplified) GENETICS OF THE BLUE ROAN COLOR
A Medium-level Description for Novice Genetics
Readers
Copyright Note:
Please note that all of the text information on this page was
originally composed by me,
and was typed with great thought. I have read books and many educational
web sites to contribute to my knowledge base. Some photos were donated by
people that have horses with color examples needed to provide educational
content.
I did not copy and paste from anyone else's web site, and hope
you will not copy and paste from my site.
Please feel free to link to this page, but do not copy the
content and place it on your site.
|
|
Genetics
Roan vs. Gray
Shades of Roan Non-roan Roaning
Foal Coat Colors
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). 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, and because they were a cross between
red and blue roan colors. But to me, if a horse is
genetically a bay with roan, it is not a true 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.
Red Roan (sorrel based)
AQHA calls these "Red Roans" but many
people refer to them as "Strawberry Roans." |
Bay Roan (bay-based).
Note the BAY face.
AQHA now correctly wants 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.
Back to Top
The Basics of Blue Roans
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:
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
Back to Top
The First Oversimplification
Remember that I am going to oversimplify on this whole
page in an attempt to make this a quicker and easier thing to understand.
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. |
|
If a horse has black legs, the color of the horse's body is controlled by the A
and a locus. An A means reddish 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 blue roans 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?"
A horse's body color is controlled by the black gene (E)
above. However, if a horse has black legs, its body can still be
red/brown if the horse has a dominant form of the Agouti allele.
The Agouti gene is a dominant gene, and if its dominant
form (A) 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 dominant Agouti genes, because they have black-colored bodies. This
is why blacks, grullos, and blue roans are so hard to get. 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), to know the genetics of its parents, or to have him genetically
tested (see the bottom of this page for information). 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.
Back to Top
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 very rarely found because it is theorized
that the fetus dies in-utero when it carries two roan genes.
Some exceptions do reportedly exist, so there is controversy as to
whether the RR embryo does die or not. See Equine Color Genetics by Dr. Phillip Sponenberg,
1996, p. 58 for more information on this theory. |
|
Newsflash! Dr.
Anne Bowling of the University of California at Davis disproved the
above theory before her death recently. The original study that
started that theory of lethal homozygous fetuses was never replicated,
and she did a study and proved that the percentages of foals with and
without color followed the statistical projection as if there was NO
lethal state. So, according to the modern research (2002, I
believe), it is just fine to breed two roans together. Statistics for
live foals will match any other color matings. |
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! Back to Top 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 |
Foal #4
|
Born black/brown |
Shed off blue roan (black head) |
Foal #5
|
Born chestnut |
Shed off liver-based roan
(red roan), which is genetically the same as
strawberry/red roan. |
Foal #6
|
Born sorrel, but showing some roaning.
Some do and some don't show roaning right from birth. |
Shed off red roan/strawberry roan |
Back to Top
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.
Roan:
| 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. |
| Roans do NOT turn lighter and lighter as years go by.
They always retain their dark-colored heads, legs, manes, and tails. |
| Roans can have any color under the roan, from sorrel,
to buckskin, to grullo. Any color of horse can also be a roan if it
had a roan parent and if it expresses the roan gene. |
| Most roans will be intensely-colored during the winter
(they will look much like a non-roan), but will be roaned out during the
summer. |
Gray:
| 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. |
| Grays usually begin turning gray by weaning time,
although some rare cases do not show much graying until they are 5 or more
years old. |
| Grays may darken a little in the winter, but each
spring, they shed out a little lighter until they are finally their final
shade of gray/white/fleabitten 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.
Learn more about Roan vs Gray colors by
clicking HERE.
|
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. |
Blue roan face of a Tennessee Walker. Note that the roaning is
less around the eyes. Normally, this is true of roans,
but with some variations and exceptions. |
Gray. Note that the face is lighter than the body, and
the tail is lightening. This horse will eventually become
nearly white or fleabitten gray. |
Back to Top
White ticking is a unique and eye-catching roan-like
pattern of white hairs that is mainly concentrated in the flank
area. This ticking can spread toward the top of the hip and toward
the withers, but doesn't cover the whole hip, belly, back, and neck of a
horse like roaning caused by the roan allele does. It often appears
in conjunction with coon tail, which is white striping at the top of the
tail.
Specific kinds of ticking include that caused by the
sabino and by rabicano patterns. Click
here to learn more about white patterns other than roan.
| This attractive ticked horse is
Absolute Investment, a rabicano-patterned Quarter Horse stallion. Click his
name to see his web page, or his photo to see the white ticking up
close. |
Absolute Investment |
| This little pony is neither roan nor gray, and is
probably exhibiting lots of sabino white pattern. |
Lauren and Frosty |
| Gray. Click here to
learn more about grays, and how to tell them apart from roans. |
|
| |
|
Back to Top
Click here to request help determining your
horse or foal's color 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.mustangs4us.com/Horse%20Colors/roan.htm Test your foal or horse...how to be SURE of his/her
genetics! Click
here
for the University of California at Davis's genetics test form. http://www.vgl.ucdavis.edu/horse/redfactr.htm
Red Factor Test KIT for sending in samples to have your horses tested.
Or, visit
www.petdnaservicesaz.com for an alternative testing site (may be
cheaper).
http://www.hancockhorses.com/article-roanQHNews.pdf Article about
HOMOZYGOUS ROAN study. This page last updated
10/22/07 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 |
|
