SILVER REGISTER
Please note that DNA testing for Silver and Agouti may be required for Silver registration. The registration process and forms are available for downloading by clicking on the Forms link (left).
The fourth of the 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 colour 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 colour 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 colour 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 colour-modifying genes, it is a simple dominant -- only one Z
gene is necessary to give the colour, 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" colour 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 colour, 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 colour 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 colour 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 colours). 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 colours, 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 colour 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 colour 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 colour, often
described as a "dead grass" colour, or a light pewter-grey
shade with light mane and tail, white eyelashes and vertically striped
hooves (on legs with no white markings).
Below: Black silver foal - note pewter-grey colour of coat
Below: Black silver
Below: Black silver Welsh D stallion.
Below: Black silver Morgan mare.
Silver on Bay
The Silver gene acting on a bay base colour 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 colour, 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 colour is "Bay Silver", but occasionally they are called "Red Silver" (reflecting the red body colour), 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 colour 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 colour. 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.
Classic bay silver
Below: Bay Silver shortly after birth and at 4 months. She has retained the real red pigment body with dappled points not black and Silver mane and tail. Note the dark skin around the muzzle in the newborn photo.
Below: Bay silver foal only several hours old and at weaning. Note the BLACK feet and DARK skin around the muzzle in the newborn. Chestnut foals in comparison are born with pinky coloured feet and skin.
Below: Another bay silver foal
Below: DNA tested Silver Bay part-Welsh stallion. Carries alleles for both Agouti (bay) and Extension (red). He has a genetic makeup of Ee & Aa - the presence of E in dominant form means that he is a genetic black base, NOT a chestnut and the presence of A in dominant form means that he carries Agouti which modifies the distribution of black pigment in their coat ie restricts it to the points and leaves the body a red colour. (A homozygous or true black will always test recessive for Agouti (aa) meaning that they have nothing controlling the distribution of black pigment in their coat hair so it is uniformly distributed across their entire body).
Below: 2 Bay Silver Morgan stallions. Note that coat remains an undiluted reddish colour whilst the black on the legs is diluted to a chocolate brown colour.
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 colour 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 colours -- if the horse looks like it's black-based but tests "AA" or "Aa", then it's not black, it's brown.
This miniature horse mare (below) is believed to be a Brown Silver because she appears to be a classic silver with chocolate coloured body and silver flaxen mane and tail. Her foal colour was pewter-grey with a silver mane and tail (like the black silver foal above) which rules out her being a Bay Silver. However, her dam is black brown and her sire the same colour as her and given the rareness of true homozygous blacks, it is therefore more logical to presume that she is genetically the same colour as her mother - black brown.
Silver
on Chestnut
Since a chestnut horse (or any other red-based colour) 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.)
DNA verified chestnut carrying silver.
With the development of a DNA test for Silver, chestnuts that have been positively DNA'd for silver or who have produced silver foals from non-silver partners are now eligible for Silver registration with Dilutes Australia.