I still remember my first acquaintance with buckskin horses. I met two girls when I was out riding one day, they weren't local and came from across the fen somewhere. Each was riding a pale pony with a dark mane, tail and points. The two were matched in size and conformation but one was a rich cream and the other a stunning golden color. Even though I was a kid I was struck by how strikingly handsome they were.
Buckskin horses are horses with a base coat color of bay or brown (i.e. of genotype Ee or EE at the extension locus) and genotype C+CCr at the C locus (the cream dilution gene). Their bodies vary in shade from pale cream to a deep rich golden color. Their manes and tails are dark, either black or very dark brown. The coat may change shade with the seasons.
Smoky black horses are sometimes called black buckskins or (especially in the UK) dilute blacks. These are black horses with a cream gene. They may be very difficult to identify and may look brown, bay, liver chestnut or faded black. The CCr allele is semi-dominant and dilutes red pigment to yellow in a single dose but has only a very subtle effect on black pigment. The wild-type C+ allele is effectively recessive since it needs to be homozygous for there to be no dilution of the base color.
Gowers model of agouti affects on buckskin
According to the Gower model the agouti locus affects the shade of buckskin. Different alleles of the agouti locus seem to be responsible for different shades of cream and yellow, as well as affecting the distribution of dark pigment.
A summary of the assumed effects of the A series on base color and buckskin is shown in the table below. Genotypes are shown using an underscore, e.g. AA_. This represents where an allele can either be the same as the allele shown (i.e. AA in the example) or any other allele recessive to it (i.e. either At or Aa in the example, but not A+ which is dominant over all other alleles). Allele Aa is recessive to all the other alleles at the agouti locus. The At (brown), previously only hypothesised, has now been shown to exist, and there is a molecular test for it.
| Genotype at the agouti locus
|| Bay horses
|| buckskin horses
|| Light bay
|| Cream buckskin
| AA AA
|| Bay, possibly having a redder coat than AA_
|| probably golden buckskin
|| probably standard buckskin
|| brown, mouse or sooty buckskin
| Aa Aa
|| smoky black
breeding buckskin horses