Dun is the same as buckskin, or so I’ve heard people say. Not at all! Although it may look similar at first glance, it is very different. A dun horse carries a dilution gene that washes out its body color, leaves color on its points, and causes darker “primitive” markings. These markings are a stripe down the back that extends into the tail (dorsal stripe), horizontal stripes on the legs (leg bars or zebra stripes), bars on the ears, and strong shading across the withers and shoulder (shoulder bars). The face is usually darker and sometimes there are concentric rings on the forehead. These markings can be very strong, or hardly noticeable if the horse has another dilution at work.

The endangered Mongolian Wild Horse (also called the Taki or Przewalski’s horse) is the last living example of a truly wild horse. They are uniformly bay dun, with a modifier called pangare (PAN-guh-ray) that also occurs in domestic horses and causes the light underside and muzzle. (There is no known genetic marker for pangare. It’s possible that there is one, but it has not been discovered. It is very common in some breeds and can occur with any color but black.)

taki
(Image from Wikipedia)
These are Taki. You can see the dark stripes on their backs and stripes on their legs, but they are are pretty washed out by the pangare. Horses this same color are depicted in Ice Age cave paintings in Europe, like this 17,000 year old painting from the Lascaux cave in France.
lascauxhorse
(public domain, via Wikipedia)

This gene acts very much the same on our domestic horses, causing the body color to be diluted and “primitive” markings to be laid down. If a horse is dun, we indicate that in genetic terms as “D”. If it doesn’t have dun, it is nd1 or nd2. (Yes, there are two versions of the recessive non-dun, and we will get to that a little later.) Dun is a dominant gene and, unlike cream, it doesn’t matter if the horse has one or two copies of it. A Dnd2 horse will look the same as a DD horse. It can act on any coat color, so you can have any base coat or any other dilution and put dun on top of it. But for simplicity’s sake, we will look in depth at two shades of dun, red dun and bay dun.

First, here is a red dun. This is a horse who is red (chestnut or sorrel) with dun. Genetically, this horse is eeD_. She is not a Heart of Phoenix horse. This lovely Quarter Horse mare is with Kentucky Equine Humane Center and she comes to this blog courtesy of Olivia Dixon.
reddun1
As you can see, her body color has been diluted to a peachy color, while her points are still red. She has a stripe down her back that starts at her withers and extends into her tail.
reddun2
She also has very distinctive shoulder barring and even some barbs on her neck.
reddun3
Her legs show very clear zebra stripes.
reddun4
And she has extensive cobwebbing (concentric dark circles) on her head. You can also see that her ear tips are dark red, as well.
This lovely mare has dramatic primitive markings and is a beautiful example of a red dun.

Our next horse is another Quarter Horse, Cash, who is owned by one of our wonderful HOP volunteers. He is a bay dun, which is E_A_D_. His body color is diluted, his head is darker, and he has primitive markings. You can also see bars of darker color at his withers and in the center of his back.
cash2
cashdorsaltail
His dorsal stripe is clearly defined and extends into his tail.
cashlegbars
And, he has clear barring on his legs.

One final dun example is Sassy, a Quarter Horse owned by another fantastic HOP volunteer.
IMG_3228
She is also a bay dun, but is much lighter than Cash. Not knowing her bloodlines and working only from her beautiful buttermilk color, I suspect she carries a copy of cream in addition to dun, making her A_E_CRcrD_.

A black horse with dun is called a grulla (grew-ya) and its body will be anywhere from slate gray to a light mousy gray, but it will keep its black points and darker head.
heckhorses
image via Wikipedia

These are Heck horses. The breed is uniformly grulla with pangare.

I mentioned earlier that there are two versions of the recessive non-dun gene, nd1 and nd2. Neither version causes true primitive markings and coat color dilution, but nd1 causes markings called countershading that imitate primitives, while nd2 does not cause any countershading.
I have a good example of a likely nd1 bay horse here.
20170703_183046
This is my 31-year-old Arabian mare. She is body clipped because she is a hairy old beast and that has distorted her color somewhat, but she has a strong dorsal stripe and faint leg and shoulder barring. It is harder to see because of the clipping. When not clipped, her coat is a bright red bay without any hint of dilution, with a dorsal stripe that runs from withers to tail, darker shading over her shoulders, and faint stripes on her legs. Genetically, she is E_ Aa nd1_. I know she cannot be dun  because dun is not present in modern purebred Arabians. In fact, Arabians do not carry any known coat color dilution genes, outside of a few individuals carrying very recent genetic mutations.

Horses that do not carry dun or nd1 are designated genetically as nd2 and do not have primitive markings or coat color dilution.

That’s it for dun! Next time we will take a look at the silver dilution.