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Locus Information: Z locus

Inheritance: autosomal dominant*

→ Horses with only one copy of the variant (Z/n) will show the same phenotype as horses with two copies of the variant (Z/Z). However, an eye problem associated with Silver in some breeds is incomplete autosomal dominant: horses with two copies may be at higher risk of developing “Multiple Congenital Ocular Abnormalities (MCOA)”.

General Information:

  • Silver results in the decreased storage of the black pigment “eumelanin” in hair.
  • Horses with a Chestnut base color may be carriers for the Silver mutation but do not develop the diluted coat color themselves.
  • The mane and tail of Silver horses are usually of lighter color than the coat → may lead to confusion with “Flaxen” or dark chestnut colors.
  • The Silver mutation is associated with eye problems in some breeds.  Especially in gaited breeds, horses with one copy of the variant (Z/n) may have a milder form of MCOA while homozygous horses (Z/Z) may develop more severe symptoms.

Possible Genotypes:

Base Color
Black Bay Chestnut
+ 1 copy of Silver (Z/n)

Silver Black

Silver Bay

Not affected by dilution but may pass the variant on to its offspring.
+ 2 copies of Silver (Z/Z)
→ Same phenotype as heterozygous horses (Z/n) but at a higher risk of developing MCOA with more severe symptoms.


Test information: This test detects a mutation in the PMEL17 gene.

Brunberg, E., Andersson, L., Cothran, G., Sandberg, K., Mikko, S., Lindgren, G.: A missense mutation in PMEL17 is associated with the silver coat color in the horse. BMC Genetics 7:46, 2006. Doi: 10.1186/1471-2156-7-46.

Andersson, L.S., Wilbe, M., Viluma, A., Cothran, G., Ekesten, B., Ewart, S., Lindgren, G.: Equine Multiple Congenital Ocular Anomalies and Silver Coat Colour Result from the Pleiotropic Effects of Mutant PMEL. PLoS One 8:e75639, 2013. Doi: 10.1371/journal.pone.0075639.

Further information is available at Online Mendelian Inheritance in Animals.


The Silver dilution is usually obvious on a black horse.  However, a Silver bay may look very similar to a chesnut horse with flaxen.  A chestnut horse may carry silver, but not show it.

Test #: H206

Samples: Blood, Hair

Price: 35 € (net)

Time required: 10-14 days

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