The Horse Colors Site

The Silver (AKA Silver Dapple) Gene

Silver is a dominant gene in the dilution category.  (Remember, dominant means you only need one gene to get a visible effect, and dilution type genes are those that cause the color to be lightened in some way.)  It is a simple dominant; there is no visual difference whether the horse has one Silver gene or two.  The symbol for this gene is "Z" (nobody seems to know why that letter was chosen, but "S" would have been confusing since many colors begin with that letter, and maybe just about everything else was taken).  The gene was isolated in 2006, and there is now a test for it.

This color has been known for 30 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".

The Silver gene is interesting because, unlike other dilution genes such as Champagne and Dun, this one is what's called pigment-specific.  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), and 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.

How It Works

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 often 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 often 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

Silver on a black base color is the shade that comes to mind first 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 most 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.  Thankfully, there are now genetic tests that will tell for sure. The normal name for this color is "Black Silver", but sometimes you might see them called "Classic Silver Dapple", "Chocolate Silver", "Chocolate", or just "Silver".

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, testing will distinguish them from chestnuts. The most usual term for this color is "Bay Silver", but occasionally they are called "Red Silver" (reflecting the reddish 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.

Silver on Brown

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 may be needed to tell apart black-based from brown-based dilute colors.

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.

Combinations

The silver dapple color can, like any color, occur in combination with any of the various other dilution (i.e. Cream, Dun, or Champagne) or spotting (i.e. pinto, appaloosa, etc.) genes.  In some cases the combinations can make it difficult to identify the presence of the Silver gene.  When Silver and Cream are both present, the effects of the Silver gene tend to be less obvious, or even not really visible at all.  This would seem to be counterintuitive since Cream makes the mane and tail of a palomino white, and Silver makes the mane and tail of a black silver white (or nearly white, usually), but oddly enough they seem to almost cancel each other out instead of doubling the dilution effect.

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 very common color, but it does occur in the Welsh Pony, Welsh Cob, Quarter Horse, Paint, Morgan, Saddlebred, Tennessee Walker, Missouri Foxtrotter, Bashkir Curly, Chincoteague Pony, and likely in the Appaloosa, Mustang, Dutch Warmblood and Paso Fino. There are even reports of it possibly occurring in the Arabian, but these have never been proven.  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.

More info

There is an excellent website on the silver dapple colors at: http://www.silverdapplemorgansproject.com

Although focused on Morgans, the color info is applicable to any breed.

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