Horse colour demystified: the dun gene

29 04 2007

Grulla mustang

Grulla mustang stallion. Image source

The dun gene is easily the most misunderstood of all the colour genes. Let’s get this out of the way first: buckskin and dun are not the same thing. A buckskin with a dorsal stripe does not automatically become a dun; they are two separate genes (though a horse can have both; more on that in a moment) and horses without the dun gene can be linebacked. Like cream, dun is dominant: a horse must have a dun parent in order to be dun itself. It’s not thought to manifest differently in its homozygous and heterozygous forms; research is still being done on that. Like champagne, it shows on both red-based and black-based horses. As yet there is no genetic test for dun but you can participate in a current study which is working towards that goal.

Dun is considered a “primitive” colour, and many wild and feral horse populations are exclusively or almost all dun: Sorraias, Tarpans, and Przewalski’s horses to name a few. Norwegian Fjords are all dun, though with different base coats.

Tarpans

Tarpans. Image source

Przewalski horse

Equus caballus przewalskii. Image source

By now you should be noticing that the body colour of dun horses is diluted to a flat or mousy shade. Duns also have a dorsal stripe running from the withers into the tailhead, with some frosting, same colour as the body shade, on either side of the line in the tail. Frosting is often present in the mane as well; see the lovely grulla at the top of this entry. Duns also show leg barring, ear striping/edging, and may exhibit cobwebbing on the head as well. For the best explanation of dun markings, with lots of photos of duns with different base colours, see Dun Central Station.

A chestnut horse with the dun dilution is called a red dun:

red dun

Chestnut + dun = red dun. Image source

Bay duns are the most likely to be confused with buckskins and vice versa, but the colour differences are quite obvious when you see them together. You can also have brown-based duns, which are darker than the bay-based ones.

Bay dun Icey

Black + agouti + dun = bay dun. Image source

Bay dun

Bay duns are also called zebra duns. Image source

Compare the flat colour and primitive markings with the golden coat of a true clear-coated buckskin:

Buckskin New Forest Pony

Black + agouti + cream = buckskin. Image source

Notice that the grazing New Forest mare above has “normal” black stockings, with no leg barring; she also lacks a dorsal stripe or any mane/tail frosting, and her coat colour is more golden than the bay duns above her.

Dun on black is called grulla or grullo (grew-yah or grew-yo); the body colour is diluted to a flat grey, silvery or mousy shade, which allows the other markings to be seen clearly.

Smokinblue Hollywood

Grulla QH stallion Smokinblue Hollywood

Like Model Ts, Fjords come in almost any colour so long as it’s dun. Image source

One reason so many people are confused about dun is that foals are often born with primitive markings, which shed out as they mature. These are a form of camouflage, like the spots on fawns or lion cubs. If someone says their foal was born dun but shed out another colour, this is what they’re seeing.

Just to add to the fun, dun can be combined with other genes. A dunalino is a red-based horse with the cream and dun genes.

Dunalino

Red + cream + dun = dunalino. Note the flat body colour and leg barring. Image source

A dunskin is a bay horse with the cream and agouti genes.

Dunskin

Black + agouti + cream + dun = dunskin. Note the tailhead frosting and leg bars. Image source

Finally's Mr. Amos

Black + agouti + cream + cream + dun = perlino dun. See his page for photos of his dun markings

In addition to the breeds already mentioned, dun has been found in Quarter Horses, Paints, Appaloosas, Mustangs; it is rare in Morgans and TWHs; does not exist at all in Thoroughbreds, Standardbreds, Arabs, or Welsh cobs/ponies. if you can help me amend this list, let me know!

Suggested links:

Dun Central Station

EquineColor.com: Dun

Colours of the Norwegian Fjordhorse

Grullo or Grulla

The Sorraia Horse

Related posts:

New dilution gene found

Recent breakthroughs in colour genetics

Silver dapple update

Dappled things

Brindle horses

What’s dun is dun

Starving horses were part of an unusual breeding program

One for Ripley’s?

Horse colour demystified: the basics

Horse colour demystified: the cream gene

Quiz: what colour horse would you be?

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16 responses

28 11 2007
Rain

Paso Fino’s also have this colouring in the breed u might wanna check it out ;)

6 08 2008
Ely Jones

Love all of the horses on this website, very beautiful!!!

18 09 2008
thorouguebred

There is a perlino 2 year old stud colt at the barn I board my horses. The lady that owns him keeps him inside a stall except when she’s working him. She’s terrified he’ll get cancer like an older mare she had. Is this a problem for these lighter skinned horses?

16 02 2009
Olivia

I love horses!!!!!!!!!!!!! Great photos!!!!!!!!!
~Olivia~

16 02 2009
Jennifer

Wonderful Horses Photos. i love horses!!!!!!!!!!!!!!!!!!!!!! My favorite horse is Tennesse Walking horses!!!!!!!!!!!!!!!
~Jennifer~

16 02 2009
Marie

I have 2 horses! One is a Tennesse Waiker gelding and the other is a spotted Quarter horse and it is a gelding too!!!!!!!!!!!!!!!!!!!!!!!!! I love them! They are so cute!!!!!!!!!!!!
~Marie~

9 08 2010
Alexi

I have Quarter horses too! i have a gelding (Mushu) and a mare (Juicy Fruit)
and i LOOOOOVEEEEEEE them! they are my babies! Juicy is a dunskin and her mom was a dun

18 02 2009
Raquel

Is it possible to have the aby dun colourings on an Arabian?

3 03 2009
Jealoushe

Don’t forget Connemerras, I have a dun one.

3 03 2009
Pet Doctor’s Blog » Blog Archive » Another breakthrough in colour genetics (or, if you prefer, “They’ve more or less dun it”)

[...] Quiz: what colour horse would you be? Horse colour demystified: the dun gene [...]

28 05 2009
Sary

Top horse is Sundowner .. registered Spanish mustang stallion standing at the Cayuse ranch, owned by Aileen Brislawn Glonek

24 12 2009
Shirley

I have a Walker filly that is registered as a buckskin, however she is NOT a typical buckskin. She is more like a mouse or squirrel coloration. I would love to send you pictures of her & get your comment. Her dam was a dark bay & her sire was a smokey cremello. She has red, black, grey, brown & silver mingled hair coloration with an irregular stripe down her back. Ther mane & tail is basically black with red highlights. I’m confused. Sincerely, Shirley

9 01 2010
shelby

I LOVE HORSES XOXO THEY ARE SO PRETTY AND GORGOUS

5 07 2010
Simrat

The top photo was taken by myself. Please either credit me with a link to my site http://simratkhalsa.com/ or remove the photo. Thank you.

He is, indeed, a registered Spanish Mustang owned by my cousin, Aileen Brislawn Glonek.

20 07 2010
horse for sale

Thanks for the link to Dun Central Station. It’s interesting to find out how genetically, horses get their color.

20 09 2010
Kirsty

I love HORSES O.M.G
Ive loved HORSES all my life and O.M.G thay are so PRETTY…..:)

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