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Dominant
curly
coat
in
horses
DP
Sponenberg
Virginia-Maryland Regional College of Veterinary Medicine,
Department of Pathology,
Virginia
Tech, Blacksburg,
VA
2.¢061,
USA
(Received
18
January 1989; accepted
20 December
1989)
Summary -
Records
from
the
American
Bashkir
Curly
Horse
Registry
indicate
that
of
457
registered horses,
25
had
no
curly-coated
parents
and
this
occurred
in
purebreds
of breeds
where
curliness
is
rare,
224
had
1
curly
coated
parent,
122
had
2
curly
coated
parents,
and
86
had
parents
of unknown
status.
Complete production
records
on
some
individuals
have revealed that
matings
between
curly
coated horses
produced
47
curly
coated and
11
normal coated
offspring. Matings
between
curly
and normal coated horses
produced
29
curly
and 17
normal coated
offspring.
The results
are
consistent
with
a
dominant
gene
causing curly
coat
in
horses,
although
a
separate
previously
documented recessive
gene
for
curliness also
exists.
The
symbol
Crd for dominant curliness
is
suggested
for the dominant
gene.
horse
/
curly
coat
Résumé - Dominance de
la
robe à
poils
bouclés chez le cheval .
L’analyse
des
457
dossiers
de
l’American Bashkir
Curly
Horse
Registry
a
montré
que
25
chevaux provenaient
de
parents
sans
robe
bouclée,
22.j
avaient
un
parent
à robe
bouclée,
122 avaient les
deux
parents
à robe bouclée
et
86
provenaient
de
parents
chez
lesquels
cette
information
était
inconnue. Les 25 chevaux
issus
de
parents
sans
robe bouclée
appartenaient
à des
races
où la
robe bouclée
est
rare.
Une étude détaillée de certains dossiers
a
révélé
que
l’accouplement
entre
chevaux à robe bouclée
a
produit
47
chevaux à robe bouclée
et i1
chevaux à robe
normale,
tandis
que
l’accouplement
entre
chevaux à robe bouclée
et
chevaux à robe normale
a
produit
29 chevaux à robe bouclée
et
17 à robe normale. Ces résultats
indiquent
la
présence
d’un
gène
dominant causant la robe bouclée bien
qu’un gène récessif
ait
été décrit
antérieurement.
Le
symbol
Crd
est
suggéré
pour
le
gène
dominant
responsable
de la robe
à
poils
bouclés.
cheval / robe
bouclée
INTRODUCTION
Horses
having
a
curly
coat instead
of
the usual
straight
hair coat
have been
documented
as
resulting
from
a
recessive
gene
in Percheron horses
(Blakeslee
et
al,
1943).
A
further
report
concerning
curliness of Lokai
horses has
appeared
in
Animal
Breeding
Abstracts
(Shchekin
and
Kalaev,
1941).
This
report
states that
such curliness
is
recessive,
but
goes
on
to indicate that
curly
x
curly matings
produced
46
curly
and 13 normal coated
foals,
and
curly
x
normal coated
matings
produced
17
curly
and
20 normal coated foals. These data
are more
consistent with
a
dominant mode of inheritance
(x2
=
0.277,
1
df,
P
>
0.05 for
curly
x
curly
matings,
2 =
0.243,
1
df,
P
>
0.05 for
curly
x
normal
matings).
In the translated
abstract mention is made of the fact that &dquo;about
one
third of
curly
offspring
from
matings
of
curly
parents
show
a more
marked
degree
of curliness
at
birth,
and it
is
thought
that these
may
be
homozygotes.&dquo;
It
is
possible
that the abstract
was
mistranslated,
and
that the
original
stated that the curliness
is
dominant.
MATERIALS,
METHODS AND RESULTS
The data
presented
are
those of the records of the
American
Bashkir
Curly
Horse
Registry.
These
horses
are
registered
on
the basis of
a
curly
coat.
Of
457
registered
horses,
224
had
1
curly
and
1
normal
parent
(curly
sires
produced
74
curly
colts
and
84
curly
fillies,
curly
dams
produced
36
curly
colts and 30
curly
fillies),
122 had
2
curly
parents
(63
curly
colts and
59
curly
fillies),
25
had 2 normal
coated
parents
(12
curly
colts
and
13
curly
fillies),
and
86
were
of unknown
parentage.
Most
of
these
457
originated
in
feral herds
in
the
West
of
the
USA
or were
the
products
of
crossing curly
feral
horses with established normal
haired
breeds
(Quarter
Horse,
Appaloosa,
Paint).
These
curly
horses
are
said
to
have other
phenotypic similarities,
such
as
bulging
foreheads,
slanting
sleepy
eyes,
small nostrils and
a
peculiar
odour.
Some
normal coated horses
of
these lines also have
some
of the
same
phenotypic
characters
so
these
may
not
be
pleiotropic
effects of the
gene
for curliness.
One
difference
between
normal coated horses
and
some
of
the
curly
ones
is
that
the
mane
and
tail hairs of
some
but
not
all of the
curly
horses
are
shed
in
springtime along
with the thick winter
body
coat.
This
phenomenon
only
occurs
in
some
individuals.
The
25
curly
horses
resulting
from
matings
of
parents
with normal coats occurred
in normal
coated breeds
(1
Tennessee
Walking
Horse,
11 Missouri
Foxtrotters,
2
Appaloosas,
4
Quarter Horses,
1
Standardbred,
1 Paso
Fino and
12
others).
These
and
the other
curly
types
cannot
be
reliably
distinguished
by
phenotype.
Complete
results
of
matings
were
available
for
some
individual
animals
(table
I).
Curly
x
curly matings
resulted in 47
curly
and 11 normal coated animals.
If these
are
heterozygous
for
a
dominant
gene
then
2
=
3.13,
1
df,
P
>
0.05. These
results
are
consistent
with the
action
of
a
dominant
gene
causing
curly
coat
in
horses,
as are
the
Russian
data.
Sex
linkage
is
not
present,
as
indicated
by
the studbook
data
in
which
both colts and fillies
are
produced by
a
single curly
parent
of
either
sex.
=
1.126,
1
df,
P
>
0.05.
Curly
x
normal coat
matings produced
29
curly
and
17
normal
haired
offspring.
If
these
curly
horses
are
heterozygous
for
a
dominant
gene
then
2
DISCUSSION
The
recessive
mode of inheritance for curliness
in
horses has been
previously
documented,
and
some
curly
horses
are
probably homozygous
for this
gene
rather
than attributable
to the dominant
gene.
This
is
especially likely
for the
curly
horses
resulting
from
matings
of
purebred
horses of breeds
that
are
normal coated.
In
our
data
is
one
such
curly
Missouri Foxtrotter
stallion born of normal
coated
parents.
He
produced
5 normal
coated
foals after
being
bred
to
normal coated
horses. If his
record
is
removed
from
the data
of the
curly
and
normal
matings
then the result is
29
curly
and
12
normal
foals.
Under
the
hypothesis
of
heterozygosity
for
a
dominant
gene
2
ACKNOWLEDGMENTS
The authors thank the American Bashkir
Curly
Registry
for
providing
these data.
REFERENCES
Blakeslee
LH,
Hudson
RS,
Hunt
HR
(1943)
Curly
coat
in horses.
J
Hered
34,
115-118
Shchekin
VA,
Kalaev
VV
(1941)
Inheritance of curliness in the
horse. CR
(Dokl)
Acad Sci
URSS, NS,
Animal
Breeding
Abstracts
(1940)
26, 262-263, 9:
7
7.048,
1 df,
P
<
0.01
which
is
highly significant.
These
matings
therefore
produce
an excess
of
curly foals,
which would
occur
if
some
horses in
the
sample
were
homozygous,
rather
than
heterozygous,
for
curliness.
The
breeding
of
curly
horses
is
complicated by
the fact that
2
separate
genetic
mechanisms
can cause
the
curly
coat.
One
of these
is
dominant,
the other
is
recessive. It is
likely
that the
2
can
be
accurately
differentiated
on
the basis
of
the annual
shedding
of the
mane
and tail.
This is
expected
of
the dominant
gene
for
curliness,
but
not
the
recessive.
The
symbol
Crd
is
proposed
for the
dominant
gene
causing
curliness
(curly dominant).
=
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