Description

Perlino (CrCr) Horse Double-Dilute Perlino. Courtesy of Tawny Dun Stud

The cream dilution gene is one of several genes that will dilute the coat of a horse. Cream is a semi-dominant gene and has a dosage effect where a heterozygous (nCr), single dilute cream horse will show a lesser effect when compared to a homozygous (CrCr), double dilute cream horse.

Horses which carry one copy of the cream gene are identified as Single dilutes; they are heterozygous for the cream dilution gene.  In the simplest case, a bay horse with a single copy of cream is known as a buckskin, a single dilute black horse is known as a smoky black and a single dilute chestnut or sorrel horse is known as a palomino.  Single dilute horses have a 50% chance on passing the cream gene on to its offspring. 

Horses which carry two copies of the cream gene are referred to as double dilutes; they are homozygous for the cream dilution gene.  A bay horse with two copies of cream is known as a perlino, a black horse with two copies of cream is known as a smoky cream and a chestnut or sorrel horse that carries two copies of cream is known as a cremello.  Double dilute horses will always pass on a copy of the cream gene to its foals. 

Cream dilution is caused by a gene mutation (in this case a SNP) in exon 2 of the MATP gene and subsequently, a genetic test has been developed that tests for the presence of this mutation. There are other genes that may have an effect similar to Cream dilution but will not be detected by this test.

 
Why test for Cream Dilution?

Often people test for cream dilution to confirm that their horse is either a single or double dilute.  There are a number of dilutions that produce similar appearances as cream dilution.  For example, it can be difficult to distinguish between a bay dun (a bay horse that carries dun dilution) and a buckskin horse (a bay horse that carries one copy of cream dilution).  Cream dilution has minimal effect on black pigment in the single copy state.  Therefore, it can be difficult to distinguish a black horse from a smoky black horse.  However, some smoky black horses do appear faded, and can resemble a brown or bay horse.  It can also be difficult to differentiate between double dilute horses.  Many cremello, smoky cream, and perlino horses appear physically similar.  In this case, it is more important to test for Red/Black Factor and Agouti to determine the base color of the horse.  Testing for cream dilution in a double dilute horse will only confirm the presence of two cream genes. 

Cream Dilution Testing

Animal Genetics offers DNA testing for the MATP gene mutation responsible for cream dilution.

Cost

$25.00 US per test.

Collect sample by pulling (not cutting) 20-30 mane or tail hairs with roots attached. It is important that you pull the hairs and confirm that the actual root of the hair is being collected. The root contains the genetic material of your horse that is needed for DNA testing. Therefore, cut hair do not provide an adequate sample of your horse. Place the collected hairs of each horse in a separate zip-lock bag labeling the bags accordingly with the horses name or identification number. Download and complete a submission form for each sample and send along with payment to Animal Genetics for testing.

Results

Results are given using the following symbolic notation: