Chestnut

Chestnut horses are also sometimes called red or sorrel, depending on the region or coat shade. Since they are all genetically the same, we will use chestnut to refer to them in our posts.

Appearance

Chestnut horses have a completely red coat with red points. White markings and KIT patterns tend to show more loudly on chestnut bases.

Foals		Chestnuts are usually born a lighter shade (especially on the legs/ soft parts) because of foal camo. The first foal shed is often very dark, and not related to their adult shade.

Foals

Chestnuts are usually born a lighter shade

(especially on the legs/ soft parts) because of

foal camo. The first foal shed is often very dark,

and not related to their adult shade.

The shade can range from yellowish, red-brown to nearly "black" (this is not actual black, but rather very concentrated red pigment). Mane and tail can be the same or a lighter shade than the body.		Adults

The shade can range from yellowish, red-brown

to nearly "black" (this is not actual black, but

rather very concentrated red pigment). Mane and

tail can be the same or a lighter shade than the body.

Adults

Mimics

Other colours can look similar to chestnut.

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Look at the points of the horse
Look at the coronet bands (area right above the hooves)
These should be reddish in colour

Genetics

Chestnut is a base colour controlled by the extension gene. In horses that are homozygous recessive (e/e), black pigment can't be produced. The result is a fully red, or chestnut horse.

There are two different recessive alleles: e and e^a.They have the same effect and can't be differentiated visually.^.The e^a ("alternate") allele is rare and has only been found in Black Forest, Knabstrupper, and Canadian horse breeds. It can currently only be tested at the UC Davis laboratory.

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Chestnut:
e/e
e/e^a
e^a/e^a

Since chestnut is caused by two recessive alleles, breeding two chestnut-based horses will always result in a chestnut-based foal. Two black or bay-based horses, however, could produce a chestnut foal if both are carrying an e-allele. This can lead to some surprises when a chestnut foal with a pedigree full of black or bay-based horses suddenly pops up!

Presence in horses

Although recessive, chestnut (based) horses are very common and widespread. Chestnuts can be found in most horse breeds; some, such as the Haflinger, are even exclusively chestnut in colour. It has been nearly eliminated in breeds like the Friesian Horse, known for its black color. However, since the e-ellele is recessive, it can stay hidden for many generations. This can result in surprise chestnut babies even in breeds like this.

Read more:
Black | Bay | Palomino | Cremello
Extension | Agouti

Back to Base Colors

Articles

Marklund, L., Moller, M. J., Sandberg, K., & Andersson, L.; A missense mutation in the gene for melanocyte-stimulating hormone receptor (MCIR) is associated with the chestnut coat color in horses, Mammalian Genome, 1996; 10.1007/s003359900264

Wagner, H-J., & Reissmann, M.; New polymorphism detected in the horse MC1R gene; Animal Genetics, 2000; 10.1046/j.1365-2052.2000.00655.x