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DUN Coat Dilution


The Dun gene is a dilution gene that affects both red and black coat colour pigments. The gene is associated with "primitive marking" and has the ability to affect the appearance of all black, bay, or chestnut ("red")-based horses to some degree by lightening the base body coat.

The dark stripe down the middle of the animal's back is the most recognizable marking associated with Dun horses. Other markings include a tail and mane darker than the body coat and usually darker faces and legs. The classic Dun is a gray-gold or tan, characterized by a body colour ranging from sandy yellow to reddish-brown. Depending on other underlying genetic coat colour factors, a Dun horse may appear a light yellowish shade or a steel gray. Manes, tails, primitive markings and other dark areas are usually the shade of the non-diluted base coat colour.

The Dun allele is dominant, meaning that a horse that carries either a single copy (heterozygous) or two copies of the gene (homozygous)is dun. Unlike silver dapple gene, which affects only black-based coats, or the cream gene, an incomplete dominant which must be homozygous to be fully expressed, the Dun gene affects both black and red-based horses.

The Dun dilute gene is characterized by markings which are darker than the body colour. These markings include: Dorsal stripe (stripe down the center of the back, along the spine), seen almost universally on all duns. Horizontal striping on the back of forelegs, common on most duns, though at times rather faint. Shoulder blade stripe, the least commonly-seen of the primitive markings.


Breeds: Quarter Horses, Paints, Appaloosas, Icelandic Horses, Norwegian Fjords, Paso Finos, Peruvian Pasos and many pony breeds.

Base Coat Plus Dun Common Coat colour
Red (Chestnut) base Dun gene Red dun
Black base Dun gene Blue dun, mouse dun or Grullo/Grulla.
Bay (black base + Agouti gene) Dun gene Classic dun, sometimes called "Bay dun" or "Zebra dun"

Animal Genetics offers DNA testing for a mutation that is linked to Dun. The genetic test verifies the presence of one or two copies of the Dun mutation and presents results as one of the following:

D/D Homozygous Horse is Dun and will always produce a Dun foal
D/d Heterozygous Horse tested Heterozygous for Dun. Horse is Dun and will pass the Dun gene on to its offspring 50%
d/d Negative Non Dun

    Submit a Sample for Testing:

    To submit a sample for testing please click on ORDER and download a sample submission form. Then follow the sample collection and submission instructions.


    Cost per sample is £30. Please see our fee schedules below for bulk and combination rates.

    Equine Fee Schedule English Pounds