Champagne is a dominant trait, based on a mutation in the SLC36A1 gene. The mapping of the gene was announced in 2008, and the American Cream Draft cross was among the breeds studied. The authors of this study noted that it was difficult to distinguish between homozygous and heterozygous animals, thus distinguishing champagne from incomplete dominant dilutions such as the cream gene. However they noted that homozygotes may have less mottling or a slightly lighter hair color than heterozygotes. Anecdotal reports also note mild differences, including lighter freckling, skin and hair coat, though eye color remains the same.