Cream Dilution Explained
The cream dilution gene affects both red and black pigment and is responsible for 'diluting' the carrying horse to lighter coat shades and colours. In many breeds this is often considered a highly desirable trait. Cream dilution is the gene responsible for palominos, buckskins, cremellos and many more (see chart below).
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 an 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.
The effects that these doses have on the horse's base colouring are outlined as follows: