Several mutations exist in the prolactin receptor gene (PRLR) of cattle that cause a short, sleek haircoat.. The mutation is dominant so slick-haired cattle can have either one ortwo copies of the mutation. The assay described here detects the most-well studied mutation (SLICK1)that causes translation of a truncated PRLR of 461 amino acids. Originally described in Senepol cattle,this mutation has also been introduced into Holsteins in Puerto Rico, Florida and elsewhere. Note thatthe assay will not detect other mutations in PRLR that also cause the slick phenotype.