Cream: why one copy differs from two

Start with the base color

One Cream copy usually gives palomino on chestnut and buckskin on bay. On black the lightening can be subtle; that combination is called smoky black. The same dilution therefore does not create one identical color on every horse.

Two Cream copies give cremello on chestnut, perlino on bay and smoky cream on black. These horses are much paler, usually with pale skin and blue eyes. Photographs cannot reliably distinguish all these combinations.

Sources for this explanation [1] · [4] · [5]

Reading Cr and N

SLC45A2 is the scientific symbol for the gene involved; older papers call it MATP. Its Cream version is written Cr. A horse inherits one allele, or version of the gene, from each parent. On a Cream test, N means the tested Cream variant was not found on that copy. It does not mean that the gene is missing.

N/Cr means one Cream copy; Cr/Cr means two. One copy mainly lightens red pigment, while two strongly lighten both red and black pigment. When one and two copies produce different effects in this way, the inheritance is called incomplete dominance.

Sources for this explanation [1] · [4] · [5]

Example: two parents with one Cream copy

Suppose both parents are confirmed N/Cr and neither carries another relevant version of SLC45A2. Each can pass N or Cr. Every conception has a 25% chance of N/N, 50% of N/Cr and 25% of Cr/Cr. These are chances for each foal, not a promised pattern over four births.

The base color determines the coat name. For example, two palominos can produce a chestnut foal without Cream, a palomino or a cremello, before other coat modifiers are considered.

Sources for this explanation [1] · [4] · [5]

Why a Cream-only test can be incomplete

Pearl, written Prl, is another version of the same gene. Cr/Prl means one Cream copy inherited from one parent and one Pearl copy from the other. A horse with two different altered versions of the same gene is called a compound heterozygote. This combination can resemble a horse with two Cream copies, although it is not Cr/Cr.

Read Cream and Pearl results together where appropriate. Very pale appearance alone does not establish which combination the horse carries.

Sources for this explanation [1] · [4] · [5]

Sunshine and Snowdrop: other versions of the same gene

Cream and Pearl are not the only versions of SLC45A2. Sunshine was described in 2019 and Snowdrop in Gypsy horses in 2020. They are distinct inherited variants. Snowdrop is interpreted as recessive: one copy on its own can remain invisible.

The evidence for these rare variants still comes from limited families. It does not establish their frequency in every breed or the appearance of every possible combination. A test panel for Cream and Pearl may not examine them; check exactly which variants the laboratory tests.

Sources for this explanation [5] · [2] · [3]

Where the explanations come from

Laboratory resources explain which variants are tested and how to read their results. Research papers describe the evidence, discoveries and remaining uncertainties. Each article links its explanations to the relevant sources. Published titles stay in their original language so you can find the exact work.

1. 1 · Laboratory explanation

   UC Davis VGL — Cream

2. 2 · Research paper

   Bisbee et al. (2020) — Identification of a novel missense variant in SLC45A2 associated with dilute snowdrop phenotype in Gypsy horses

3. 3 · Laboratory explanation

   LABOGEN — Snowdrop: genetic testing and interpretation

4. 4 · Research paper

   Mariat et al. (2003) — A mutation in the MATP gene causes the cream coat colour in the horse

5. 5 · Research paper

   Holl et al. (2019) — SLC45A2 variants, pearl and sunshine