What is Silver Dapple?
Silver Dapple, also called just Silver, is a color-modifying gene in the "dilutions" category, so called because they dilute, or make lighter, some or all of the pigments which give the horse its color. There are at least five different dilution type genes, although only three of them have been found in the Saddlebred breed (Cream, Champagne, and Silver). They are all separate genes and all work differently. The Silver gene (gene symbol "Z") is a simple dominant gene, meaning you only need one copy for it to be visible, and a horse that is homozygous for the gene (ZZ) looks no different than a horse that is heterozygous (Zz). A horse that has no dominant copy of the gene (zz) is not diluted, does not carry the gene, and cannot pass it on.
The Silver gene works by diluting black pigment only (not red) to a chocolate or liver color. The body shade can vary from a light cocoa to near-black, depending on the base color. The legs are usually left somewhat darker than the body, and the mane and tail are usually diluted to a near-white, platinum or flaxen color (although they may darken with age until they are nearly the same shade as the body). Typically, a bay with a Silver gene will look like a bay horse with a flaxen mane and tail (the legs will be more of a chocolate color rather than the jet-black of a bay, but may look black from a distance), and a black or brown with a Silver gene will be the typical "silver dapple" color of chocolate with a white or near-white mane and tail. These are very similar in appearance to a dark liver chestnut with flaxen mane and tail, or a chocolate palomino, and it may not be possible to tell those three colors apart by appearance alone, but genetic testing can tell which color the horse is. Whatever base color the silver dapple is on, they are usually registered as "chestnut", since that is the closest category matching their appearance. (The gene is not expressed on a true chestnut horse, since they have no black pigment to be affected, only red pigment. However, they could carry the gene and pass it on to their foals.) The dapples may or may not be present, but if they are, they are large and highly contrasted. They may come and go with the seasons. For some reason they are much more common in the pony breeds than the horse breeds.
For a full explanation of the Silver gene please see this page: http://www.horsecolor.com/dilutions/silver_dapple.htm
There is an excellent website which discusses the history and discovery of the Silver Dapple color in the Morgan breed here: http://www.silverdapplemorgansproject.com/
Discovery of the Silver Dapple color in Saddlebreds
Silver Dapple was actually once thought to only exist in Shetland Ponies (about 25-30 years ago), but it's been known for a long time now that the typical "chocolate" color in Rocky Mountain Horses is usually silver dapple, and that it does exist, although rarely, in many North American breeds. Since the availability of the red-factor test, which proves that a horse is black-based, not chestnut, it has been possible to prove genetically that silver dapples are "not chestnut". At the time of this writing (2005), there is no actual test for the Silver gene as yet, but when a bay-with-flaxen-mane-and-tail or a chocolate-with-white-mane-and-tail (both likely to be registered as chestnut) horse tests as being black-based (EE or Ee), not chestnut (ee), that is proof that it is actually silver dapple -- nothing else causes that phenotype. It was documented for the first time in Missouri Foxtrotters in 2001; in Morgans, Saddlebreds, Quarter Horses and Tennessee Walkers in 2002; and in Paints in 2005. Undoubtedly there are some Mustangs and Appaloosas with this color as well, although none have been tested yet to our knowledge.
In the Saddlebred, unlike some other breeds such as the Morgan, there are not a large number of dark flaxen chestnuts or chocolate palominos -- in fact those colors are rather unusual in the breed. Chestnuts are very common, which makes it difficult to find silver dapples (remember, the color does not show on a chestnut). Thus, it was never particularly suspected in the breed. Then along came a horse named Commander's Crescent Society. A picture of this mare as a youngster (weanling or yearling) was circulated a few years ago, but it wasn't good enough to tell for sure what color she was, although she did look bay silver. Then in the summer of 2002, she was advertised for sale, and the new pictures were convincing -- this had to be a bay silver! When she was tested, sure enough, her red-factor test was "Ee", proving she is not chestnut, but bay silver dapple.
Continue to next page for info and pictures of Crescent and her foals.
At this time we are not aware of any other confirmed Silver Dapples in the breed; however, there have been some "possibles" that aren't tested yet. If anyone has any information on possible silver dapples, or any "strange looking" colors of any kind, in the Saddlebred breed, please contact firstname.lastname@example.org and help us find some more.
*** NEWS FLASH ***
October, 2006: The Silver gene has been found!!!
November, 2006: Testing for Silver is now available from a few labs. Now we can find out whether a chestnut (or other "ee" color) horse is carrying a Silver gene..... whether our silver dapples are heterozygous or homozygous...... whether horses of a base color that could hide it (i.e. grey) are silver or not..... etc. Great news!!