UC Davis School of Veterinary Medicine Veterinary Genetics Laboratory
Donkey Coat Color and Hair Length Tests

Dominant White and White Spotting | Long Hair | No Light Points | Red Factor (Extension)


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Dominant White and White Spotting

White spotting patterns occur in many donkey breeds and are similar to those of horses in that the amount of white can range from a few white hairs to an animal that is almost completely white. Two mutations in the KIT gene have been identified that cause white spotting in donkeys and they have been named dominant white (W) and white spotted (Ws). Both are inherited in an autosomal dominant fashion meaning that only one copy of either mutation is required to produce white pattern phenotypes. The genetic basis for the variability in the amount of white is not known. Homozygosity for the Ws allele is thought to be incompatible with life and our testing of one Ws/Ws foal who died by 2 weeks of age suggests that this may indeed be the case. The W allele has only been identified in a single individual born with an all-white phenotype. It is unlikely that a W/W donkey be born and viable as the mutation in homozygosity could be embryonic lethal. Lethality of W and Ws mutations remains to be confirmed.

Genetic testing is recommended for all donkey breeds known to have a white spotting phenotype. Breeders can benefit from this test to determine which mutation is present in a white patterned donkey and also to select mating pairs to avoid breeding two white patterned donkeys together as these matings may result in unviable foals.

Results reported as:

Result Explanation
N/N Normal - no copies of the identified dominant white or white spotted mutations.
N/W 1 copy of the dominant white mutation; donkey is white.
W/W 2 copies of the dominant white mutation. Predicted to be lethal in utero.
N/Ws 1 copy of white spotted allele, donkey is white spotted.
W/Ws 1 copy of the dominant white mutation and 1 copy of white spotted; donkey is predicted to be white.
Ws/Ws 2 copies of the white spotted mutation. Color is white. Predicted to be lethal.

Reference:

Haase B, Rieder S, Leeb T. Two variants in the KIT gene as candidate causative mutations for a dominant white and a white spotting phenotype in the donkey. Animal Genetics 2015 46(3):321-4. doi: 10.1111/age.12282.

Fenn, D.J., Raudesepp, T., Cothran, E.J., Hamilton, N.A., Haase, B. Validation of a candidate causative mutation for white spotting in donkeys.  Animal Genetics 2016 48:124-125 doi: 10.1111/age.12506.


Long Hair

Long hair in the Poitou breed results from two independent loss-of-function mutations in the fibroblast growth factor 5 (FGF5) gene. Both mutations are inherited in an autosomal recessive fashion. Thus, long-haired donkeys have two affected alleles. Short-haired individuals are present in the population and a genetic test is available to screen for the presence or absence of the long hair mutations.

Genetic testing for the donkey long hair mutations is recommended for Poitou donkeys and mules with a Poitou parent. Breeders can benefit from this test to identify carriers of long hair mutations and the potential of mating pairs to produce long-haired offspring.

Results reported as:

Result Explanation
N/N No copies of either Long hair allele. Animal has short hair.
N/LH1 Carrier - one copy of Long hair 1 allele. Animal has short hair.
N/LH2 Carrier - one copy of Long hair 2 allele. Animal has short hair.
LH1/LH1 Two copies of long hair 1 allele. Animal has long hair.
LH2/LH2 Two copies of long hair 2 allele. Animal has long hair.
LH1/LH2 One copy of each long hair allele. Animal has long hair.

Reference:

Legrand R, Tiret L, and Abitbol M. Two recessive mutations in FGF5 are associated with the long-hair phenotype in donkeys. Genetics Selections Evolution 2014 46:65 doi:10.1186/s12711-014-0065-5.


No Light Points

Donkeys typically have light points which describes the pale color around the muzzle, eye rings, belly and upper and inner aspects of the legs. However, donkeys in several breeds have darker pigment in these areas and are described as no light points (NLP). A mutation in agouti signaling protein (ASIP) is associated with the no light points. NLP is an autosomal recessive trait thus two copies are required for NLP to be observed. Donkeys with only one copy, also known as carriers, of the NLP variant exhibit light points but they can produce offspring that have no light points. Breeding two carriers has a 25% chance of producing a NLP foal and a 50% chance of producing a carrier.

Genetic testing for donkey NLP is recommended for Pyrenean, Berry Black, Poitou, Cotentin, Provence, Bourbonnais, Normand and American Miniature donkey breeds. Genetic testing helps breeders to determine the genetic status of breeding stock for No Light Points mutations and to select appropriate mating pairs to favor, or to avoid, producing foals with this phenotype.

Results reported as:

Result Explanation
N/N No copies of no light points. Animal has light points.
N/NLP Carrier-one copy of no light points. Animal has the light points pattern.
NLP/NLP Two copies of NLP variant. Animal lacks the light points pattern.

Reference:

Abitbol M, Legrand R, and Tiret L. A missense mutation in the agouti signaling protein gene (ASIP) is associated with the no light points coat phenotype in donkeys. Genetics Selections Evolution 2015 47:28 doi:10.1186/s12711-015-0112-x


Red Factor (Extension)

Donkeys with red body and red trim are typically described as sorrel, chestnut or simply as red. The locus governing this color is commonly called Red Factor or Extension. The mutation causing red in donkeys has been identified in the melanocortin 1 receptor (MC1R) gene and is inherited as an autosomal recessive trait. MC1R is also the gene that causes red factor (chestnut) in horses although the mutations are different. The donkey red factor is not the same allele as the horse red factor although both cause red/chestnut color. Therefore, the horse test is not informative for donkeys and vice versa. Red donkeys have two copies of the donkey ed allele. Donkeys with only one copy of ed, also called carriers, have black in the coat or trim. Breeding two carriers (Ed/ed x Ed/ed) has a 25% chance of producing a sorrel foal and a 50% chance of producing a carrier.

Genetic testing for donkey red factor is recommended for Normand, American Mammoth Jack, and American Miniature donkey breeds as well as for those breeding mules. If testing for red in mules it is advisable to test for both the donkey and the horse red factors.

Results reported as:

Result Explanation
Ed/Ed No copies of donkey red factor. Animal is wild type color.
Ed/ed Carrier - one copy of donkey red factor. Animal is wild type color.
ed/ed Two copies of donkey red factor. Animal is red.

Reference:

Abitbol M, Legrand R, and Tiret L. A missense mutation in melanocortin 1 receptor (MC1R) is associated with the red coat colour in donkeys. Animal Genetics 2014 45:878-880 doi:10.1111/age.12207.

 

 
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