~AGOUTI EXPLAINED~
by Brenda Ogden Childs


I am going to try to explain the black/blue, brown, bay issue for you all who may not grasp the whole concept and hopefully it will help you understand it and help you with foal registration and representation. First, every horse in the world; every single one, has one of two base colors... black or red. Thats it. Black, red. I am talking about BLACK base horses, genetically Ee or EE. That is NOT what makes them a true blue or black. Its the agouti status. A true black or blue is not carrying the agouti gene. Agouti means restricting black, so when the gene is not present (aa) the black pigment is distributed evenly over the coat... none is restricted, so when a horse is aa for agouti and black base, he is a true black. Add roan, and he is a true blue roan, even if he sunfades and... appears bayish. A horse that is aa can not produce bay or brown foals, only black or blue, when black based.

The most common agouti that we all know well is bay. Its Aa or AA on a black base. It restricts black to the points (legs, mane, tail, ear rims, and such) allowing the red pigment to show through. It is the most dominant of the agouti genes. A horse that is AA on a black base can not produce black or blue offspring. All offspring that are black base will be bay.

The next most common is brown, yet it isn't as widely accepted and is commonly argued. Brown is the least restrictive of the agouti genes. Brown is genetically Ata, or when homozygous AtAt. Brown only restricts the black at the soft points, like the muzzle, eyes, flanks, and so on. Many brown roans look blue and are registered as such because you can not register them as brown roan. There is only one lab that tests for brown, its PetDNA. When a horse carries brown and bay genes, it will be bay because bay is dominant. So, that means when a horse is brown, it can not produce a bay foal because it is not carrying that gene. It can only produce brown, and if heterozygous, blue. If you register a brown as a blue and it produces a brown foal, you will be forced to change the papers to bay before being able to register the foal. Don't make that mistake!!!!

The least common and most restrictive is wild bay. There is no test so not a lot is known about it, but for now it is known as A+. Wild bay restricts black to just above the cornet band and to the mane and tail. It can be hard to recognize if you are not familiar with it, and often leaves some dun countershading, but is NOT dun or related to it in any way. It is, at this time believed to be recessive to bay, and dominant to brown. Until there is a test for it we wont know much more. PetDNA is working on a test.

- I hope this helps clear up some confusion with black/blue, brown and bay. When I have more time I will give some info on grey and sooty as they tend to cause confusion as well. Let me know if you have any questions :)

Dwayne and Sunday Blue
Gordon, TX 76453
Home: 940/769-2609
E-mail: raisinroansranch@live.com

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