Silver Dapple
The last of the four genes in the "dilutions" category is called
Silver Dapple, or just Silver. The gene symbol is "Z".
This gene has been known for 25 years or more, but is only
recently becoming better understood. The name Silver Dapple
was originally applied to Shetland Ponies, in which the color is
fairly common (at one time it was even thought that the gene only
occurred in Shetlands), because it frequently has the extremely
dappled, greyish body color with silver-white mane and tail in
that breed. Now we know that not all (possibly, not even most)
of them are dappled, so the name has been shortened from Silver
Dapple to just Silver. The term "Silver" has been confusing to
some,
who expect to see a grey-toned horse perhaps, but it has been in
use too long to change. In Australia the color is called
"Taffy",
but the term has never caught on elsewhere. In some of the
breeds in which Silver is common in the USA, such as the Rocky
Mountain Horse, it is simply called "Chocolate".
How It Works
Like most color-modifying genes, it is a simple dominant -- only one
Z gene is necessary to give the color, and homozygous Silvers (ZZ)
look no different than heterozygous Silvers (Zz). With this particular
gene, though, there is a little twist -- like the Cream gene, the Silver
gene is pigment-specific. They are basically opposites -- while Cream
(when heterozygous) dilutes only red pigment, Silver dilutes only black
pigment. Thus, the Silver gene can be carried and "hidden" by a
chestnut horse (since it has no black pigment to be diluted) just as
the Cream gene can be carried and "hidden" by a black horse (which
has no red pigment to be diluted). In this way it can appear to skip
generations, even though, like any dominant gene, one parent must
have the gene in order for the foal to have it.
When a horse gets the Z gene, any black pigment will be diluted to
a chocolate-brown, ranging in shade from taupe or "dead grass" color
through mocha-brown to deep chocolate brown, often with a bluish
cast. It can be hard to tell apart from a dark liver chestnut, but usually
the dark chestnut will have reddish undertones and the Silver will not.
The gene tends to dilute the mane/tail much more strongly than the
body, often to a silvery-white color, although this can vary and they
may darken with age. Silvers usually have a distinct "face mask"
of
darker hair which is helpful in identifying them. This "mask"
generally
covers the forehead, around the eyes, and down the front of the nose.
They also tend to have lighter hair on the lower legs, lightest close
to the hooves. Foals usually have hooves with a very strong and distinct
striping pattern, and white eyelashes. These traits are helpful for
identifying Silver in foals, but are gradually outgrown.
Silver on Black
Some common names for this color are "Classic Silver Dapple",
"Chocolate Silver", or "Black Silver". This is the
shade that comes to
mind when hearing the term "Silver Dapple". The body color is
diluted
to a chocolate-brown or mocha-brown shade, sometimes light enough
to appear similar to a sooty palomino. The mane and tail are often
near-white, a striking contrast. The lower legs are usually lighter than
the rest, almost flaxen near the hoof, and the lower legs are often dappled
(which is highly unusual in other colors). The mane and tail often have
dark roots. In a horse with the "classic expression" of Silver
Dapple,
there will be very distinct and strong dappling present, which, unlike
most colors, does not appear to be related to age or condition, but
rather stays fairly constant throughout the horse's life -- although they
may vary with the seasons, appearing on the summer coat but not the
winter coat, usually. But not all Silvers show the dappling. Some
are
a flat chocolate-brown color all year round. Silver on black can be hard
to tell apart from a dark flaxen liver chestnut, and in many breeds they
have indeed been registered as "chestnut" because nobody knew what
they were. Some clues to look for would be the dappling, a drastic change
in color from winter to summer, a bluish cast rather than a reddish tone,
and a silvery mane/tail rather than golden-hued flaxen. Still, it may be
impossible to tell the difference by looking. Luckily, a red-factor test
will distinguish between a silver and a chestnut!
Foal-coats are generally a light greyish-tan color, often described as a
"dead grass" color, or a light pewter-grey shade with light mane and
tail,
white eyelashes and vertically striped hooves (on legs with no white markings).
Silver on Bay
The Silver gene acting on a bay base color gives a quite different effect.
The red pigment on the body is unaffected, while the black on the legs
is slightly diluted and the black of the mane/tail is more strongly diluted.
This gives the appearance of a horse that is not quite bay, and not quite
chestnut either. Most of the time they end up being registered as
chestnut, which can cause confusion, but most registries have no
separate category for Silver. The mane and tail can vary from a
platinum blonde, to a flaxen color, to just slightly diluted, and can
darken considerably with age, making identification more difficult.
Usually the legs are the main clue that the horse is not a chestnut --
they will be much darker than a chestnut, ranging from near-black to
chocolate-brown, generally with lighter hair close to the hooves.
And again, when in doubt, a red-factor test will distinguish them from
chestnuts. The most usual term for this color is "Bay Silver",
but
occasionally they are called "Red Silver" (reflecting the red body
color),
however, this is rather discouraged since to many people the term
"red"
means chestnut, and therefore "red silver" could cause confusion to
those thinking that it means silver on chestnut.
Foals are generally the same color as a flaxen chestnut foal. Often it's
impossible to tell the difference just by looking. Usually they will have
the
white eyelashes and vertically striped hooves, but not always, or perhaps it's
just not always noticed. One tip that is helpful is the skin color.
Typically,
chestnut foals are born with pink or pinkish skin (although this often goes
unnoticed because it darkens up within a few days), so a chestnut-looking foal
with dark skin at birth is probably not chestnut. The dark skin at birth
would
be a sign that there is an "E" gene, although grey also does this to
newborn
skin on red-based foals, so if grey were also a possibility, it wouldn't be so
helpful.
Silver on Brown (Seal)
A seal brown with the Silver gene will look similar to either a black silver,
or a bay silver, depending on how light or dark the brown's base color
happened to be. Most seal browns are mostly black, and this plus Silver
would probably be very hard to tell apart from black silver. The lighter
seal browns with more tan in the coat would give a lighter shade of Silver.
The Agouti test is useful for telling apart black-based from brown-based
colors -- if the horse looks like it's black-based but tests "AA" or
"Aa",
then it's not black, it's brown. (See Base Colors for more info.)
Silver on Chestnut
Since a chestnut horse (or any other red-based color) has no black
pigment to be affected by the Silver gene, they will show no effects.
Such a horse would be called "chestnut carrying silver". Some
breeds
use the term "Silver Chestnut" but this is highly discouraged by
geneticists,
because it tends to confuse people, making it sound like the chestnut
horse is somehow affected by the Silver gene. In some breeds, some
breeders apparently think that the Silver gene can cause a flaxen mane/tail
on a chestnut horse; however, this is not true. ("Old wives'
tales" die hard.)
Breeds That Have This Color
This color is not frequently seen except in a very few breeds -- the Shetland,
Mini, and Icelandic have quite a few, and there are a few breeds in the USA
which have purposely selected for the color so that now many horses
of those breeds, perhaps even most in some cases, are Silvers: the
Rocky Mountain Horse, Mountain Pleasure Horse, and Kentucky Mountain
Saddle Horse.
Aside from those breeds, it is not a common color at all, but it does occur
in the Welsh Pony, Welsh Cob, Quarter Horse, Tennessee Walker, Missouri
Foxtrotter, Bashkir Curly, Saddlebred, Morgan, and Dutch Warmblood, Paint, Appaloosa, Mustang, and Paso Fino. There are even reports of
it
possibly occurring in the Arabian, but these have not been proven yet. It
is
thought to have been in the Friesian breed in the past, but no longer. It
also
is known to occur in some draft breeds such as the Belgian, Breton, Comtois,
Noriker, and Italian Heavy Draft.
How to get a Silver Dapple
Like any dominant gene, you need at least one parent with that gene, in order
for the foal to get it. But since Silver can be carried unexpressed by a
chestnut, even through many generations, this can make for some interesting
results.
To get a Black Silver, you need:
-- One parent Black Silver, or Bay Silver with an "a" gene
and
-- One parent any color as long as they have at least one "a" gene.
*or*
-- One parent chestnut carrying the Silver gene, and not "AA"
and
-- One parent any color, as long as it has at least one "E" and one
"a".
To get a Bay Silver, you need:
-- One parent Bay Silver
and
-- One parent any color.
*or*
-- One parent Black Silver
and
-- One parent any color as long as they are not "aa".
*or*
-- One parent chestnut carrying the Silver gene
and
-- One parent of any color, as long as it has at least one "E", and,
if the
chestnut parent happened to be "aa" then the other parent would need
to have at least one "A".
*Note that "any color" means any base color. Naturally if the
horse were
homozygous for grey, roan, pinto or any other modifiers, then this would
combine with the Silver and change its appearance.
