Agouti

A black or brown/bay coat colour can only arise if a horse is either a non-carrier (E/E) or a carrier (E/e) for the red coat colour. The Agouti gene determines whether the horse develops a black or a brown coat. A horse homozygous for the recessive allele of the Agouti gene (a/a) is black. In a carrier or non-carrier horse (A/a or A/A), the black pigment appears only in certain areas like mane or tail and the horse is brown/bay. The colour inheritance for specific pairings follows the same rules as described for the red factor. For breeding purposes, the Agouti gene is mainly important as a “hidden” feature in red coloured horses.