Agouti (A)

In real life only the “A” gene is testable and the shade of chestnut is not possible to predict.

Thankfully, Helix’s work has paid off and you are able to test and breed for various agouti types:

 

  • A+ – A+ is the gene that creates Light Chestnut horses.
  • A – A is the gene that creates Red Chestnut horses.
  • At – At is the gene that creates Standard Chestnut horses
  • a – Horses that have “aa” genes will be Liver Chestnut.

Agouti Hierarchy

Should you manage to have a horse with two types of agouti variations, there is a hierarchy that these genes follow:

A+ > A > At > a

Light Chestnut > Red Chestnut > Standard Chestnut > Liver Chestnut

Horses with the A+ gene will display the chestnut base associated with A+. As stated above A+ creates the light chestnut base coat thus any horse that is A+a, AtA+, or AA+ will be light chestnut.

 

Light Chestnut

Red Chestnut

Standard Chestnut

Liver Chestnut

Extension (E)

The Extension gene (E) controls how black and red pigment are produced. The presence of E (Ee or EE) means your horse will produce black pigment. The absence of E (ee) means your horse produces only red pigment.

Black horses will always be EE or Ee with their agouti gene “aa”.

Black = Ee aa or EE aa

 

 

 

Extension (E) & Agouti (A)

Extension (E) and agouti (A) genes interact with each other to create bay base coats.

 

If a horse has both extension (E) and agouti (A) the base coat will be bay. Since bay horses have the agouti gene, there are also shades for bays.

In combination with at least one extension gene agouti will make:

  • A+ – A+ is the gene that creates Light Bay horses.
  • A+A+ – Two A+ genes creates Wild Bay horses.
  • A – A is the gene that creates Bay horses.
  • At – At is the gene that creates Brown Bay horses.
  • AtAt- Two At genes creates Seal Bay horses.
  • a – Horse will not be bay.

Agouti Hierarchy

Should you manage to have a horse with two types of agouti variations, there is a hierarchy that these genes follow:

EE or Ee

with

A+ > A > At

Light or Wild Bay > Bay > Brown or Seal Bay

Horses with the A+ gene will display the chestnut base associated with A+. As stated above A+ creates the light chestnut base coat thus any horse that is A+a, AtA+, or AA+ will be light chestnut.

 

Light Bay

Wild Bay

Bay

Brown Bay

Seal Bay