Coat Color in Horses
The basic coat color of a horse is determined by the following genes:
White (W), Gray (G), and E and A. The first two genes, W and G are dominant (need only one
copy to produce the white or gray color). While these horses may contain genetic variations at
the E and A locus, these variations cannot be determined by inspection of the coat or skin.
In the absence of one or two copies of the W or G genes, the coat colors of Bay,
Chestnut/Sorrel and Black are controlled by variations at the E and A locus as seen in the
following table. VetGen currently offers DNA testing for Black, Chestnut, Cream dilution and
Silver Dilution.
Genotype Coat Color
EEAA
Bay/Wild Bay
EeAA
Bay/Wild Bay
EEAa
Bay/Wild Bay
EeAa
Bay/Wild Bay
eeAA
Red (Chestnut/Sorrel)
eeAa
Red (Chestnut/Sorrel)
eeaa
Red (Chestnut/Sorrel)
EEaa
Black
Eeaa
Black
All other colors are variations of the above core colors, and are controlled by other genes that
have not yet been located and for which no test exists.
Once your horse has been tested and you know its genotype, use this table for breeding
strategies and breeding stock selection. The outer ring of the color buttons shows the visible
coat color. The inner rings show the hidden color genes carried by the horse. Entries in the
table show the probabilities of producing each of the various coat colors for a possible foal. For
example, if your results show that your horse is a Genotype eeAa, your horse is a chestnut
horse carrying the hidden genes for black. If you were to mate this horse with a Genotype
EEaa, the resulting foal would, on the average, have a 50/50 chance of being black or bay.
These probabilities represent expectations averaged over the long run and are subject to the
law of probabilities.
Coat Color Inheritance Chart for Horses
EEAA
EeAA
EEAA
Bay-100
Bay-100
EeAA
Bay-100
Bay-75
Red-25
Bay-100
EEAa
Bay-100
Bay-100
EEAa
Bay-100
EeAa
Bay-100
Bay-75
Red-25
eeAA
Bay-100
Bay-100
eeAa
Bay-100
Bay-50
Red-50
Bay-50
Red-50
eeaa
Bay-100
Bay-50
Red-50
Bay-50
Black-50
EEaa
Bay-100
Bay-100
Eeaa
Bay-100
Bay-75
Red-25
Bay-50
Black-50
Bay-50
Black-50
Bay-75
Black-25
Bay-75
Black-25
Bay-75
Black-25
EeAa
Bay-100
Bay-75
Red-25
Bay-75
Black-25
Bay-56
Red-25
Black-19
Bay-50
Red-50
Bay-37.5
Red-50
Black-12.5
Bay-25
Red-50
Black-25
Bay-50
Black-50
Bay-37.5
Red-25
Black-37.5
eeAA
Bay-100
Bay-50
Red-50
Bay-100
eeaa
Bay-100
Bay-50
Red-50
Bay-50
Black-50
Bay-25
Red-50
Black-25
Red-100
EEaa
Bay-100
Bay-100
Red-100
eeAa
Bay-100
Bay-50
Red-50
Bay-75
Black-25
Bay-37.5
Red-50
Black-12.5
Red-100
Red-100
Red-100
Red-100
Bay-50
Black-50
Red-100
Red-100
Red-100
Black-100
Bay-100
Bay-50
Black-50
Bay-25
Red-50
Black-25
Black-100
Black-100
Black-100
Red-50
Black-50
Black-100
Black-75
Red-25
Bay-50
Red-50
Bay-50
Red-50
Bay-50
Black-50
Bay-50
Black-50
Bay-100
Eeaa
Bay-100
Bay-75
Red-25
Bay-50
Black-50
Bay-37.5
Red-25
Black-37.5
Bay-50
Red-50
Bay-25
Red-50
Black-25
Black-50
Red-50
While a test for the W and G genes does not yet exist it should be noted that:
In the presence of the dominant allele W, a horse from birth will typically lack pigment in skin
and hair. The skin is pink, the eyes brown (sometimes blue), and the hair white. Sometimes
such a horse is called albino. The W allele is only rarely encountered. All non-white horses are
ww. The homozygous condition (WW) is lethal.
A young horse with a G allele will be born with any color but gray and will gradually become
white or white with red or black flecks as an aged animal. Earliest indications of change to gray
can be seen by careful scrutiny of the head of a young foal, since often the first evidence of the
gray hairs will be seen around the eyes. In intermediate stages of the graying process, the
horse will have a mixture of white and dark hairs, a most confusing stage for trying to identify
color. In the later age, the hair color tends to become more silver.
Cream Dilution
The cream dilution gene is has two alleles: C which does not have any effect on either red or
black pigment, and Ccr which dilutes red pigment significantly and black pigment slightly. The
coat colors that cream dilution is responsible for may be found in the table below. It should be
noted that only one copy of Ccr is needed for diluted color, and two copies produce even
further dilution. Cream dilution is found in many breeds.
CC
CCCr
CCrCCr
E_aa
black
smoky black
smoky cream
E_A_
bay
buckskin
perlino
ee__
chestnut
palomino
cremello
Silver Dilution
Silver dilution is found in far fewer breeds than cream dilution. It plays an opposite role
whereby black pigment is diluted, but red pigment is left untouched. Black manes and tails will
be diluted to a silvery grey or flaxen, and otherwise black horses will be brown. The mutant
allele is dominant, so only a single copy is needed to cause dilution, and there is no difference
between horses with one or two copies of the mutation. This mutation was discovered and
reported recently by researchers at the University of Uppsala in Sweden.
Silver Dilution Results are reported as:
NN
&nbspNo dilution
NZ
&nbspOne copy of mutation: black pigment diluted, red
pigment unchanged
ZZ
&nbspTwo copies of mutation: black pigment diluted, red
pigment unchanged