UC Davis School of Veterinary Medicine Veterinary Genetics Laboratory

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Horses have four common coat color dilution genes with defined phenotypes: Cream, Dun, Silver and Champagne. Two rare dilution phenotypes have been recognized in Quarter Horses and Spanish horse breeds such as Andalusians and Lusitanos. In Spanish horses, this dilution is known as Pearl. In Quarter Horses and Paints, it has been commonly known as "Barlink Factor". The two dilutions have been assumed to be different. Research at the Veterinary Genetics Laboratory (VGL) on the Quarter Horses/Paints identified a mutation associated with the "Barlink Factor" dilution. Further research has shown that the same mutation is present in Spanish horses with the Pearl phenotype. The presence of this mutation in Quarter Horses and Paints likely reflects the Spanish horse ancestry of these modern breeds. To recognize that this mutation probably originated in Spanish horses, it is appropriate to name it Pearl.

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

Pearl Dilution results are reported as:

N/N No copies of Pearl dilution detected.
N/Prl One copy of Pearl dilution detected.
Prl/Prl Two copies of Pearl dilution detected.
Veterinary Genetics Laboratory, Tel 530-752-2211, Email VGL