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Champagne,
a
dominant color
dilution
of
horses
DP
Sponenberg
AT
Bowling
artment
of
Biosciences
and
Pathobiology, Virginia-Maryland
Regional College
of
Veterinary
Medicine,
Virginia Tech, Blacksburg,
VA
2l061;
2
Veterinary
Genetics
Laboratory,
School
of
Veterinary
Medicine,
University
of California
at
Davis, Davis,
CA
95616-8744,
USA
(Received
3 June
1996;
accepted
2
July
1996)
Summary -
Champagne
dilution
of
horses
results
in
a
group
of
pale
colors
which have
mottled
dusky
skin and amber
eyes.
Body
color varies from
light
brown
to
gold
or
cream.
Eye
color
of
champagne
foals
is
blue,
and
darkens
to
amber
with
age.
The
mating
of
champagne
to
nonchampagne
horses resulted
in 54
champagne
and
40
nonchampagne
foals. These results
are
consistent with
a
dominant
gene
(2
=
2.1,
1
df,
P
>
0.1).
This
)
at
the
Champagne
(Ch)
locus.
This allele
dilutes black
to
pale
brown with
dark brown
points,
dilutes
bay
to
yellow
with
brown
points,
and dilutes chestnut
to
gold
or
yellow
with
yellow
or
pale
points.
horse
/
genetics
/
coat
color
/
champagne
dilution
Résumé -
Champagne :
un
gène
dominant
de
dilution
des
couleurs
chez
le cheval.
Chez
le
cheval,
le
phénomène
de dilution des couleurs
appelé
«
Champagne»
produit
un
ensemble
de couleurs claires allant
avec une
peau
noirâtre tachetée
et
des
yeux
couleur d’ambre. La
couleur du
corps
va
de
brun clair
à
or ou
crème.
La couleur de 1’oeil des
poulains
champagne
est bleue et
s’assombrit
vers
l’ambre
avec
l’âge.
Des
accouplements
de
champagne
avec
des
non-champagne
ont
donné
54 poulains
champagne
et
40
non-champagne,
ce
qui
s’accorde
avec
l’hypothèse
d’un
gène
dominant
2
=
2, 1,
p
>
0, 10). Il
est
proposé
que
le
gène
responsable
de cette dilution soit considéré
comme
l’allèle
champagne
(C
INTRODUCTION
Dilution
of color
in
horses
is
associated
with several different
genetic
mechanisms,
and each mechanism results in
a
distinct
group
of
colors
(Sponenberg
and
Beaver,
1983).
Early
work
confused
some
of
these
mechanisms,
and attributed the actions
of
two
loci
to
a
single
locus
(Castle
and
King,
1951;
Castle and
Singleton,
1961;
1 D
dilution
is
proposed
as
due
to
the
champagne
allele
(C
)
au
locus
Champagne
(Ch).
Cet allèle dilue le noir
en
brun clair
à
points
bruns
foncés,
le bai
en
jaune
à
points
bruns,
et
l’alezan
en or ou
jaune
à
points jaunes
ou
clairs.
cheval / génétique /
couleur de la robe
/
dilution
champagne
Salisbury
and
Britton,
1941;
Singleton
and
Bond,
1966).
The
present
understanding
of horse color
genetics
is
that dilution
is
accomplished by
three
distinct
genetic
mechanisms
(Castle
and
Smith, 1953;
Adalsteinsson,
1974;
Van Vleck and
Davitt,
1977;
Adalsteinsson,
1978;
Sponenberg
and
Beaver, 1983;
Craig
and Van
Vleck,
1985;
Lauvergne
et
al,
1991).
This
paper
provides
evidence of
a
fourth color
dilution
locus
for the horse.
The cremello allele
at
the
Albino
locus behaves
as an
incomplete
dominant
(Adalsteinsson, 1974).
The result of the
heterozygous
state
is that
phaeomelanin
is
lightened
from red
to
yellow,
and eumelanin is
unchanged. Bay
is
therefore
diluted
to
buckskin,
chestnut
to
palomino,
and black is either
unchanged
or
diluted
vary
subtly
to
smoky.
The result of the
homozygous
state
is that both
phaeomelanin
and
eumelanin
are
changed
to
cream.
The skin is
pink,
and the
eyes
are
blue.
On
any
base color the
homozygous
state
results in
cream,
although
subtle differences from
different base colors
may
persist
on some
horses. The cremello
allele,
on
its
own,
does
not
cause
the distinctive
striping
patterns
which
are
characteristic of another
equine
dilution locus.
The dun allele
at
the Dun locus results in
the
linebacked dun
group
of
horse
colors. It is
a
dominant
allele,
with identical
appearance
of
heterozygous
and
homozygous
horses
(Adalsteinsson
1974, 1978;
Van Vleck and
Davitt, 1977;
Craig
and Van
Vleck,
1985).
The dun allele dilutes
phaeomelanin
from red
to tan
or
light
red,
and eumelanin from
black
to
pale
beige
or
blue. The
dun allele
has minimal
dilution effect
on
the
mane,
tail,
and lower
legs.
Distinctive
stripes
down the
back,
over
the
withers,
and
on
the
legs
are
also characteristic of
the
dun colors.
As
a
result
of the dun
allele,
bay
is
changed
to
zebra
dun,
chestnut is
changed
to
red
dun,
and
black
is
changed
to
grullo.
The
actions
of dun and
cremello
are
not
additive,
so
that
horses
with
both
alleles
are
only subtly
different from those
with
only
one or
the
other. The
horses with both alleles tend
to
retain the
striping
associated
with
dun,
and the color is diluted
to
the
maximal
extent
of either the dun
or
the cremello
allele.
Bay
is
changed
to
light gold
or
yellow
zebra
dun,
chestnut
to
linebacked
palomino,
and black
to
grullo.
Horses that
are
homozygous
for cremello
and
also
have dun
are
usually
cream
colored
with
striping
typical
of
duns.
The silver
dapple
allele
at
the Silver
Dapple
locus is
a
third
genetic
mechanism
for dilution of horse color
(Castle
and
Smith,
1953).
The silver
dapple
allele is
dominant,
and
heterozygous
and
homozygous
horses
are
similar. Phaeomelanin is
not
conspicuously
changed.
Eumelanin is diluted
to
pale
sepia.
The dilution is
greatest
in
mane,
tail,
and lower
leg.
The result
on
black is silver
dapple,
the classic
form of which is
a
dappled sepia
with
very
pale
mane,
tail and lower
leg.
The
action
of the silver
dapple
allele
is
variable,
though,
and sometimes its
presence
is
associated with
only
minimal
dilution
of
eumelanin.
Bay
is
changed
to
red
silver,
which retains the red
body
of
bays
but has
typical changes
associated with the
silver
dapple
allele in the
mane,
tail and
legs.
Chestnut
is
changed
minimally,
if
at
all,
because
chestnut
phenotypes
are
phaeomelanic,
and
the
silver
dapple
allele
therefore
can
have
no
action.
A
group
of horse colors that is
distinct
from the three
previous
dilute color
groups
consists of horses with amber
eyes
(which
are
blue
a
birth and then
darken)
and
light
colors all of which tend
to
have
a
bright
metallic sheen. Horses with these
colors
are
sometimes born
a
dark
color,
which then
lightens
with
age.
This is
the
reverse
of
most
colors of
horses
(Sponenberg
and
Beaver,
1983),
and
contributes
to
the confusion
surrounding
these
colors. The skin of these horses
is
dusky pink
with
dark
mottling.
This skin
color is darker
than
that of
the
skin of
horses
homozygous
for cremello and
is
lighter
than
the
skin of
horses with dark
color
or
with dilute
color from
the
other
three
genetic
mechanisms. The colors of
this
group
lack
the
striping
typical
of dun horses. This
group
of colors
occurs
in
a
number of breeds
as
a rare
variant.
One of the colors
within this
group
of
dilute
colors is metallic
light
brown
with
darker brown
mane
and
tail,
which is
the
color called
champagne by
Tennessee
Walking
Horse breeders. In the
past
this
color has been
registered
as
buckskin
or
chestnut,
probably
for lack of
a
suitable alternative
designation
by
registration
authorities.
The
champagne
color does
not
fit
the definition
of
either
buckskin
or
chestnut.
A
second
variant
within
the
group
has
a
yellow body
and brown
mane,
tail,
and lower
legs.
This
variant
is
frequently
registered
as
buckskin
despite
the
brown
(rather
than
black)
mane,
tail and
legs
and the
eye
and skin
characteristics
typical
of
the
champagne
group
of colors.
A third
variant
has
a
gold
or
yellow
body
and
legs,
and
light gold
or
flaxen
mane
and
tail.
This
color is
frequently
registered
as
palomino although
these
horses
have
the
amber
eyes
and
mottled
dusky pink
skin
associated
with
the
champagne
color
group,
unlike
the
palominos
arising
from
the
cremello allele. In
addition
to
their
occurrence
in
the Tennesse
Walking
Horse,
these
colors have been
noticed
in
Spanish Mustangs
and
ponies
of
uncertain
breeding.
The
group
of colors
including
champagne
was
studied
in order
to document
their
mode
of
inheritance.
MATERIALS
AND
METHODS
The
complete
results
of
mating
individual
champagne
dilute
stallions
and
mares
were
available,
and
are
presented
in table I.
These
included several Tennessee
Walking
Horses,
and
one
Spanish Mustang.
The
matings
were
all
to
nondilute
mates. The
production
records
of
other individual
horses
with the
champagne
allele
were
studied
to
determine
the
colors
resulting
from
the
presence
of
the
champagne
allele with
various
background
color
genotypes.
This included horses for which
complete
records
were
not
available,
and
these
records
are
presented
in
tables
II
and III.
RESULTS AND
DISCUSSION
The
matings
from
champagne
dilute horses for which
complete
data
were
available
produced
54
champagne
and 40
nonchampagne
foals. Under the
hypothesis
that
the
champagne
allele is
dominant,
X
=
2.1,
1
df,
P
>
0.1.
This allele
is
proposed
as
the
champagne
allele
at
the
Champagne
locus.
All horses that
produced
brown foals
with brown
points
(the champagne color)
also
produced
black
foals,
indicating
that
they
had
genotypes capable
of
producing
black foals. The
champagne
color
was never
produced
by
horses who failed
to
produce
black foals. The
mating
of
champagne
horses
to
black mates
produced
six
champagne
and five
black foals.
These
findings
are
consistent
with
champagne
color
being
the
result of
the
champagne
allele
on an
otherwise
black
background.
Horses
with
gold body
color and
yellow
or
white
manes
and
tails
consistently
reproduced
this color
or
chestnut
following
mating
to
chestnut
mates.
This
is
consistent with
the
gold
color
resulting
from
the action
of
the
champagne
allele
on an
otherwise chestnut
background.
Horses
with
yellow body
color
and brown
points only
were
produced by
matings
that could also
produce bay
genotypes,
and
it is
likely
that the
yellow
with brown
points
color
results
from
the
action
of
the
champagne
allele
on an
otherwise
bay
background.
In
some
instances
horses
with
gold
bodies and
light
manes
and
tails
were
mated
to
palomino
mates.
Some of the
resulting
foals
were
ivory
or cream
colored,
with
mottled
dusky
skin and dark bluish
green eyes.
One such
ivory
foal
was
mated to
a
chestnut
mare
and
reproduced
the
ivory
color.
The
ivory
color
is
probably
the
result of the
heterozygous
condition
fo both
the
champagne
and
the cremello alleles.
If
this
is
true,
then
these
two
dilutions
are
additive. Extensive
breeding
tests
have
not
yet
been
accomplished,
but the
reproduction
of
the
ivory
color from
a
chestnut
mare
indicates that
the
two
alleles
are
not
at
the
same
locus,
since
they
appear
to
be
segregating
independently.
Instances
in which
two
champagne-colored
horses
were
mated
to
one
another
were
relatively
rare,
and
only
occurred with
horses for which
complete
production
records
were
unavailable.
As
a
result,
the color of
homozygotes
is
undocumented.
In all
cases
of
champagne-to-champagne
matings,
the
specific
color
mated
together
was
the
gold
type
with
pale
points.
These
matings
produced
15
foals,
all of which
were
gold.
The
consistent
production
of the
gold
color
suggests
that the
homozygous
condition of
the
champagne
allele does
not
result in
more
extensive
dilution than
does the
heterozygous condition,
which
argues
against
an
interpretation
of
the
champagne
allele
as an
incomplete
dominant. The lack of nondilute horses
from
these
matings
is
an
indication
that
perhaps
not all foals
are
reported.
If
this
is the
case,
then
extensively
diluted foals
may
well have
not
been
reported.
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