Silver: why a chestnut can carry it unseen
The PMEL gene and its Silver version, Z
Silver mainly changes black pigment. It can be invisible in a chestnut’s coat while still being inherited and associated with eye abnormalities.
Explanations and diagrams reviewed on 3 November 2026
Which parts of the coat change
On black, Silver can produce a chocolate or gray-brown body with a much lighter mane and tail, sometimes with dapples. On bay, the effect is especially visible in the normally black mane, tail and lower legs.
Red pigment changes little. A flaxen chestnut or a sun-bleached mane is therefore not proof of Silver, and a chestnut without visible Silver effects can still carry it.
What a Silver result means
PMEL is the scientific symbol for the gene; older research calls it PMEL17. It helps organize pigment-producing structures inside cells. Its Silver version is written Z. Each parent contributes one allele, or version of the gene.
Here N means absence of the tested Silver variant. N/N has no Z, N/Z has one and Z/Z has two. One Z can lighten black hair pigment. On a chestnut base, that pigment is not produced in the hair, so the Silver effect can remain hidden even though Z is present and can be passed on.
The eye association matters on every base
The same PMEL variant is associated with multiple congenital ocular anomalies, shortened to MCOA. These are abnormalities of eye development. Horses with one Z often have milder changes, including fluid-filled eye cysts; those with two Z tend to have more extensive abnormalities. Severity varies.
A chestnut coat does not remove this association. A color test identifies the variant, while an eye examination assesses the individual horse’s eyes. These provide different information, so one does not replace the other.
Example: two N/Z parents
If both parents are confirmed N/Z, each conception has a 25% chance of Z/Z, 50% of N/Z and 25% of N/N. The distinction matters for eye health as well as coat color, because eye abnormalities tend to differ between horses with one copy and those with two.
N/Z crossed with N/N cannot produce Z/Z under this model, but it can produce N/Z foals with associated eye changes. Discuss breeding decisions and eye findings with a veterinarian; appearance alone cannot establish eye health.
An example: what could this foal inherit?
PMEL
Both demonstration horses have the exact pair shown. These examples explain inheritance; they do not use the mare and stallion entered in the calculator.
MareN/Z
StallionN/Z
All possible pairs at each conception
- N/N25%
Two copies of N
- N/Z50%
One N and one Z
- Z/Z25%
Two copies of Z
Where the explanations come from
Laboratory resources explain which variants are tested and how to read their results. Research papers describe the evidence, discoveries and remaining uncertainties. Each article links its explanations to the relevant sources. Published titles stay in their original language so you can find the exact work.
1 · Laboratory explanation
UC Davis VGL — Silver and Multiple Congenital Ocular Anomalies2 · Research paper
Brunberg et al. (2006) — PMEL17 and Silver coat colour3 · Research paper
Andersson et al. (2013) — Ocular anomalies and Silver result from mutant PMEL