The agouti gene, or bay gene, is a modifier, and will only show up if the horse is dominant black, and restricts black pigment to a horse's points; the legs, mane, and tail. Due to the fact that it will only effect black pigment, it will only have a visible affect on a black horse, agouti has no visible affect on chestnut horses. Like chestnut, it is one of the most common coat colors in horse breeds. Though easier to identify than some chestnut pigmentation, bay horses can also have a wide variety of coat pigments. The most well known is a pigmentation called blood bay.
Agouti has four different alleles; recessive (a), seal (At), classic bay (A), and wild bay (A+). The most recessive allele, a, is easily overwritten, which is a reason why black horses are so uncommon.
Agouti has four different alleles; recessive (a), seal (At), classic bay (A), and wild bay (A+). The most recessive allele, a, is easily overwritten, which is a reason why black horses are so uncommon.
The second most recessive allele is At. It restricts black pigment from a horse's soft points, making a coloring known as seal bay or seal brown.
Seal used to be thought of as a form of pangare, but further testing has confirmed it as a form of bay.
Seal used to be thought of as a form of pangare, but further testing has confirmed it as a form of bay.
The allele A is responsible for classic bay coat coloring. Classic bay horse will have black legs, mane, and tail and will sometimes have black ear tips.
Though it is only the second most dominant agouti allele, it is the most common.
Though it is only the second most dominant agouti allele, it is the most common.
Though it is the most dominant allele, A+ is also the most rare and creates a type of bay called wild bay. Wild bay horses will have lighter pigmentation than classic bay horses, and the black on their legs will only rise up to the pastern (ankle). It will have a black mane and tail like a normal bay horse, however.
Genes that are in bold are active on the coat. Genes that are underlined are genes that the horse may carry, but will have no visible effect on the coat.
Seal
Gene sequence : E_ · Aa/AtAt · gg · crcr · dd · chch · ff · zz · stysty · rbrb · rn+rn+ · sb1+sb1+ · w+w+ · to+to+ · oo · splspl · lplp · patn1patn1 · patn2patn2
Bay
Gene sequence : E_ · Aa/AA/AAt · gg · crcr · dd · chch · ff · zz · stysty · rbrb · rn+rn+ · sb1+sb1+ · w+w+ · to+to+ · oo · splspl · lplp · patn1patn1 · patn2patn2
Wild Bay
Gene sequence : E_ · A+_ · gg · crcr · dd · chch · ff · zz · stysty · rbrb · rn+rn+ · sb1+sb1+ · w+w+ · to+to+ · oo · splspl · lplp · patn1patn1 · patn2patn2