The cream dilution gene affects both red and black pigment. It is responsible for 'diluting' the horse to lighter coat shades and colors. In many breeds, this is often considered a highly desirable trait. Cream dilution is the gene responsible for the patterns of palominos, buckskins, cremellos, and many others.
Horses that carry only one copy of the cream gene (n/Cr) are identified as single dilutes; they are known as heterozygous for the cream dilution gene. Single dilute horses have a 50% chance on passing the cream gene on to its offspring. In the simplest cases, 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.
Horses that carry two copies of the cream gene (Cr/Cr) are referred to as double dilutes; they are homozygous for the cream dilution gene. Double dilute horses will always pass on a copy of the cream gene to its foals. 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 horse. A chestnut or sorrel horse that carries two copies of cream is known as a cremello.
Cream dilution is caused by a genetic mutation in the MATP gene. The MATP gene plays a role in the production of melanin, although the full scope of this gene’s functions is not entirely understood. Nonetheless, 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, however, they will not be detected by this test.
The effects that these doses have on the horse's base coloring are outlined as follows:
- No Dilution (n/n)
- Chestnut or Sorrel
- Single Dilute (n/Cr)
- Smoky Black
- Double Dilute (Cr/Cr)
- Smoky Cream
Animal Genetics offers genetic testing for the gene mutation responsible for cream dilution. We are able to tell whether or not the horse is (n/n), (n/Cr), or (Cr/Cr) for the cream mutation. Testing is useful where genetic confirmation is required or to determine cream dilute horses compared to horses with other genes with similar effects (such as champagne dilution or grey).
Running this test will confirm if a horse is cream dilute. As mentioned, the cream dilution gene has varying effects on different base colors. To obtain the exact 'type name' of cream dilute of the horse (i.e. Buckskin, Palomino, etc.), it is recommended to run this test in conjunction with the red factor and agouti tests.
|Homozygous: Horse has two copies of the Cream Dilution gene and will appear as a double dilute of its base coat. Horse will pass this gene on to all offspring.
|Heterozygous: Horse carries one copy of the Cream Dilution gene and will appear as a single dilute coat. Horse has a chance to pass this gene on to any offspring.
|Negative: Horse is negative the for the Cream Dilution.
A mutation in the MATP gene causes the cream coat colour in the horse. Mariat D, Taourit S, Guérin G. Genet Sel Evol. 2003 Jan-Feb;35(1):119-33. [PMID: 12605854]
The cream dilution gene, responsible for the palomino and buckskin coat colours, maps to horse chromosome 21. Locke MM, Ruth LS, Millon LV, Penedo MC, Murray JD, Bowling AT. Anim Genet. 2001 Dec;32(6):340-3. [PMID: 1736803]