Agouti ("A") is the genetic modifier that acts on the dominant form of the Extension locus (E) to create Bay.
"E" dominant horses are normally Black. But in the presence of Agouti, black pigment is restricted to the "points:" the lower legs, mane and tail, leaving the main body and head as red.
AGOUTI - the BAY Modifier
Bays are born with brown or red bodies but their manes and tails may be light-colored, and their lower legs are very light. They will all darken to black as they mature:
While BAY is the result of a genetic modifier acting upon a BLACK base (Actually "Dominant "E"), BAY itself can be modified to create these color patterns:
Buckskin is Bay diluted by the Creme Gene
Dun is bay with the dun gene. Bay Duns are also called Zebra Duns
Zebra (Bay) Dun Kiger horse owned by Kim Bauer of Oregon
Bay Roan is Bay with Roan gene. (red body, black points)
Red (Bay) Roan adopted by Pat Hyatt of California
Champagne on Bay
Callie, owned by Cathy Hill
LIVER CHESTNUT is a red-based color pattern that can closely mimic Bay. Liver Chestnut horses are dark red to almost black in body color, with darker, sometimes black, manes and tails. Their lower legs, however, are not black and thus they can be distinguished from bays by their lower legs.
If you see a Bay-like horse whose points are not quite black, or a Bay-like horse with black mane and tail but red legs, that is a Liver Chestnut.
This liver chestnut Morgan would be a bay except his lower legs are not black
HOW IT WORKS:
Black or Red is determined on the section (Locus) of the DNA strand that is called the Extension Locus. The Extension locus can be either dominant or recessive. It is called "E" (if dominant) or "e" (if recessive) in genetic notation.
Horses with two recessive "e" "genes" are red.
Dominant "E" is normally black. However, the dominant "E" gives the horse the capability of producing both red and black hairs. This happens when "E" is modified by the "A" or Agouti gene.
The "A" gene (Agouti) restricts black (which would otherwise cover the entire horse) to the "points," leaving the body red.
Agouti has no effect on a Red base coat, since Red has no black to restrict. Agouti can be carried by a red horse, however, and transmitted to offspring. Thus, a red and a black horse can produce bay offspring if the red horse carries Agouti.
University of California, Davis, began in 2003 to offer a test for Agouti (Bay/Black).
Wild-Type Bay ("A+")
Wild Type Bay also refers to an effect that mimics, and may also be partially caused by, the Pangare/Mealy gene, with the muzzle, underside, flanks, and behind the elbow lightened.
Color genetics are the same for all horses, regardless of breed or ancestry.
Since this is a Mustang website,
|Genetic Technicals (in case you are feeling
the need to become confused....):|
They're describing the same thing, just using different letters.