The genetic defect leading to the disease has been identified. By DNA testing the responsible mutation can be shown directly. This method provides a very high accuracy test and can be done at any age. It offers the possibility to distinguish not only between affected and clear horses, but also to identify clinically healthy carriers. This is an essential information for controlling the disease in the breed as carriers are able to spread the disease in the population, but can not be identified by means of common laboratory diagnostic.

Champagne

Champagne is a dominant gene that dilutes hair pigment from black to brown and red to gold.
A dominant gene means that only one copy of the Champagne gene is enough for the gene to make effect.
The Champagne gene makes the following alterations:

Hair

On chestnut background it produces a gold body colour and often a fairer coloured main and tail (this can be mistaken for Palomino).
On Bay background produces a darker tan body with brown points.

Skin

The skin of horses carrying the Champagne dilute gene is pinkish / Lavender toned, it becomes speckled as the horse ages particularly around the eyes, muzzle, under the tail, udder and sheath.
Eyes

Blue-green at birth which darkens to amber as the horse ages.

The Champagne gene is inherited independently of the other coat colour genes and therefore this dilution may occur in combination with any other colour modification gene.

Dun is a dominant gene that dilutes the color of body hair, leaving the points and head unaffected. Dun horses also show 'primitive markings' consisting of a dark dorsal stripe, leg barring, shoulder stripes and concentric marks on the forehead (spiderwebbing, cobwebbing). The dorsal stripe appears to be a consistent feature of dun horses while the other 'primitive marks' vary and may not all be present, or visible. The effect of the Dun gene on the base colors of chestnut, bay and black produces horses with shades that range from apricot, golden, dark gray, olive, and many, more subtle, variations. Dun is inherited independently of other coat color genes and can occur in combination with any other genes that modify the base colors.

The specific mutation that causes Dun has not yet been identified, and there is no direct test for the gene. VGL has identified DNA markers associated with Dun that can be used to determine if a horse has the Dun gene and how many copies.

Explanation of Results:

• Horses with nd2/nd2 genotype will not be dun dilute and will not have primitive markings. They cannot transmit a dun dilution variant to their offspring.
• Horses with nd1/nd2 genotype will not be dun dilute, but may have primitive markings. They may transmit the non-dun 1 variant to 50% of their offspring.
• Horses with nd1/nd1 genotype will not be dun dilute, but may have primitive markings. They will transmit the non-dun 1 variant to all of their offspring.
• Horses with D/nd1 or D/nd2 genotype will be dun dilute and will display primitive markings. They may transmit the dun dilute variant to 50% of their offspring. Matings with N/N genotype will results in a 50% chance of producing a dun dilute foal.
• Horses with D/D genoytpe will be dun dilute and will transmit the dun dilute variant to all of their offspring. Matings with any genotype are predicted to produce dun dilute offspring.

Multiple Congenital Ocular Anomalies (MCOA)

The gene for silver is another gene causing a lightening of the basic colour. The silver-gene has no impact on pheomelanin like the genes for cream and champagne and only leads to brightening of black coloured areas. Especially black coloured hair of mane and tail appears brighter because of the occurrence of white and grey hairs. The gene for silver is inherited autosomal-dominant and one copy of the gene is sufficient for the phenotype.

The silver dilution is also known to be associated with an inherited ocular syndrome known as Multiple Congenital Ocular Anomalies (MCOA).

Pearl behaves as a recessive gene with respect to the hair color. One dose of the mutation does not change the coat color of black, bay or chestnut horses. Two doses on a chestnut background produce a pale, uniform apricot color of body hair, mane and tail. Skin coloration is also pale.

In Spanish horses, this dilution is known as Pearl. In Quarter Horses and Paints, it has been commonly known as 'Barlink Factor'.

Pearl is known to interact with Cream dilution to produce pseudo-double Cream dilute phenotypes including pale skin and blue/green eyes.