Dr. van Haeringen Laboratorium B.V.

P660 Coat Colour Dun dilution


During the last decades, a large number of scientific publications have described the genetic principles of coat colour and coat variation. Coat colours and coat variations are influenced by many hereditary factors. The DNA-tests are based on physiological effects in the body, in which the production and distribution of pigments result in many coat colour variants. In several cases, the coat colour of an animal may only be decided using DNA-tests.

The Dun dilution gene lightens the coat colour of the horse by lightening the body colour, leaving the head, lower legs, mane and tail undiluted. Dun is also typically characterized by “primitive markings”, allmost all dun horses possess at least the dorsal stripe, but the presence of the other primitive markings varies. Other common markings may include horizontal striping on the legs, transverse striping across the shoulders, and lighter guard hairs along the edges of a dark mane and tail. Dun diluted coat colour with primitive markings is considered the “wild-type” colour and is found in wild equids such as przewalski horses. Dun dilutes both red and black pigment, and the resulting colors range from apricot, golden, dark gray, olive and many more subtle variations. A horse can also carry mutations for other modifying genes which can further affect its coat colour. The Coat Colour Dun dilution test (P660) tests for the genetic status of the TBX3 gene. This gene has three variants (alleles); allele D is dominant over the alleles nd1 and nd2; allele nd1 is dominant over nd2. The dominant allele D results in Dun dilution with primitive markings. Allele nd1 does not dilute the coat colour of the horse, primitive markings are present but the expression is variable. Allele nd2 does not have an effect on the basic colour.

Test specific information

This test is performed by UCDavis.

Since 2015, two brands have been developed. CombiGen® is mainly directed at veterinarian applications, whereas CombiBreed® is mainly directed at breeders and/or owners.
Detailed information about Coat Colours and Coat Variation is presented at www.combibreed.com.


Most coat colours and coat types are usually visible directly after birth.

Turn Around Time

The turn-around-time of a test depends to a large extent on the logistics of sample transportation to the laboratory. After receiving the sample at the test location, you can normally expect the result within 10 working days. A longer delivery time applies to tests carried out by a Partner Lab.

Location of disease or trait

Genetic factors influencing coat colours and coat types are usually visible on the outside of an individual. Several factors may be hidden by the external variation.

Breed dependence

For this test samples from all breeds are accepted.

Sample type

For this DNA test we accept the following materials: Hair, Blood EDTA, Blood Heparin, Semen, Tissue. Please contact Dr. Van Haeringen Laboratorium if you wish to submit other material as listed.


Coat colours are based on many genetic factors. For each factor, a separate test result will be returned.


Various genetic factors influencing coat colour and coat types are inherited in a dominant or recessive mode. Coat colours are influenced by a large number of genetic factors.

Severity of Disease

Factors influencing coat colour and coat types are usually not related to diseases.

Code P660

Coat Colour Dun dilution

€ 51,43 (Incl. 21% VAT)
€ 42,50 (Excl. VAT)