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Silver, abbreviated "Z", only affects black pigment.
It has no effect on a chestnut
(red) horse.
Silver used to be called "silver dapple". It's the
dilution gene that makes the
color known as "chocolate" (in the USA) or as "taffy" (Australia) in ponies, and
which is also the most popular color of Rocky Mountain Horses. "Chocolate"
is the result of silver on solid black.
The presence of the gene is abbreviated
"Z". The absence of the gene is
abbreviated "z". It is a simple
dominant gene: one copy of the gene causes the dilution to be fully
expressed, and two copies (homozygosity) looks no different than one.
Silver on black
E_, aa, Z_
Silver dilutes the mane & tail of a black horse, at
least partially, to flaxen
or a silvery-white, and the body to walnut (very dark) brown.
This rescue pony is the result of a cross between two very common silver
carriers: A Rocky Mountain Horse mare and a Shetland Pony stallion.
Silver on bay
E_, A_, Z_
Silver dilutes the mane & tail of a black horse, at
least partially, to flaxen
or a silvery-white, and the body to an orangey-red. It dilutes the
black lower legs to dark brown.
Silver on bay can look similar to flaxen chestnut, except
that the lower legs are diluted black rather than chestnut red.
This is one way to distinguish a sooty flaxen chestnut or palomino from a bay
silver. This silver bay Rocky Mountain Horse stallion belongs to Ann
McFadden,
http://www.romancevalleyrockies.com, who graciously gave us permission to
use his photo here.
Silver on brown
E_, AtAt or Ata, Z_
"Wilbur", owned by Carolyn Shepard of Paso Robles (Rancho No Robles), CA. DNA
verified AtaEEZzToTo. Thank you, Carolyn!
While Wilbur's a really cool guy, Carolyn has rightly pointed out that his
darker lower legs are not very visible due to his "chrome". So, I'm also
attaching this additional photo from Angela Robichaud of a rare brown silver
Morgan stallion: Schaenzer's Silver Eagle of www.rainbowsgaitranch.com.
I can't help but point out that although his lower legs ARE dark, his
fetlocks and pasterns (ankles) are lighter. This is also true of Dollar,
the bay silver, above.
First, lets' find out whether these two tested E and Z. Then, let's
quit using light ankles as the determining factor in deciding that a horse is
"really a flaxen, sooty chestnut/palomino" and not silver.
Silver combinations
As long as there is a black E gene in the horse's DNA, silver combined with
any other dilutions will have an affect on the horse's appearance. Silver
on dun, champagne, or cream, or combinations of any of those, will usually
produce a flaxen amen & tail.
For example, silver on bay plus dun would tend to produce a flaxen mane &
tail on a diluted red body with darker legs and striping (silver dun).
The miniature horse is one good place to find combinations of these genes.
The ICHR has several miniature horses registered that are silver plus dun plus
champagne on black or bay or brown. Often, the manes and tails of horses
with these combinations are simply "lighter", rather than completely flaxen or
silver-white.
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