This mutation dilutes the horses coat whether they carry one or two copies
Breeds known to carry this mutation
Many, including Quarter Horses and related breeds, Paint Horses, Miniature Horses and American gaited breeds
Champagne dilutes chestnut to a gold colour, like palomino. Classic champagne on black will dilute the horse to a dark tan colour; while champagne on bay will dilute the body to Amber with brown points. The eyes are blue green at birth and darken to amber as the horse grows.
Interpretation of results
n/n: Horse does not carry the champagne dilution allele.
Ch/n: Horse is heterozygous for the champagne dilution allele. The horse will have a diluted coat and amber eyes.
Ch/Ch: Horse has two copies of the champagne dilution allele. It will look the same as horses with only one copy but will pass the champagne allele to all its offspring.
Cook et al. Missense Mutation in Exon 2 of SLC36A1 Responsible for Champagne Dilution in Horses. PLoS Genetics 2008: 4(9):e1000195. doi:10.1371/journal.pgen.1000195