EQUINE PARENTAGE AND ANIMAL GENETIC SERVICES CENTRE

Cream dilution coat colour test

The cream gene is a dominant dilution gene that causes a reduction in red pigment if 1 copy of cream is present, and dilution of all pigment if 2 copies of cream are present.

There are two alleles- C (normal) and Ccr (cream dilution). Each individual has a pair of alleles for the cream dilution gene, one inherited from the dam and one from the sire.

One copy of the Ccr allele CCcr Æ palomino, on a chestnut base coat colour Æ buckskin, on a bay base coat colour Æ smokey black, (dilution can be minimal and difficult to detect)

Two copies of the cream allele CcrCcr Resultant coat colour is very dilute, and the eyes are generally blue. Æ cremello, on a chestnut base coat colour Æperlino, on a bay base coat colour Æsmokey cream, on a black base coat colour

The cream dilution gene is different from the dun and silver dilution genes. It can be difficult to differentiate between dun and buckskin, but with the dun dilution the primitive horse markings are always present – striping on the legs and neck, and most obviously the dark dorsal stripe. Horses can carry genes for than one of the dilution group e.g. cream and dun.

The gene variant resulting in the cream dilution has been reported (Membrane associated transporter protein or MATP)

Reference, Mariat, D et al (2003) Gent. Sel. Evol. 35, 119-135.

This study was performed on 145 horses, and extensive field validation has not been reported, but the test for cream based on this information is widely used internationally. Therefore while this laboratory is prepared to provide this test for the cream dilution variant it should be noted by horse owners using these results that the test has not been fully field validated.

Your results will be reported as follows:

CC or CCcr or CcrCcr

CC -no cream dilution

CCcr -1 copy of the cream dilution gene Coat colour - palomino ( if ee) - buckskin (if EE or Ee and AA or Aa) - smokey black (if EE or Ee and aa) A proportion of offspring will have dilute coat colours. palomino x palominoÆ25% chestnut, 50% palomino, 25% cremello eeCCcr x eeCCcr on average

CcrCcr - 2 copies of the cream dilution gene Coat colour – cremello (if ee) - perlino (if EE or Ee and AA or Aa) - smokey cream (if EE or Ee and aa)

Why test for cream or cream plus Extension and Agouti - black horses with very minimal dilution from 1 copy of cream may appear “black”, with only slightly faded coat and eye colour. They will pass the cream dilution on to offspring. - it can be very difficult to distinguish between cremello and perlino horses. If you want to know the base coat colour they will pass on to offspring they need to be tested for Extension and Agouti. - grey coat colour can mask 1 or 2 copies of the cream dilution, as well as the genotype for Extension and Agouti