Color Genetics 101

Kigers are a unique breed in that they only come in a few select colors - Dun, Grulla, Red Dun, Bay & Black being most common. (There are a few disputed colors such as red, grey and roan but that topic is outside the context of this post). I get asked fairly often to help Kiger friends decipher their DNA reports so I thought it might be helpful to write a blog post on it.

There are two types of genetic reports commonly done on Kigers. The first is a Parentage Test, required by the registries in order to document bloodlines and provide proof of parentage for foals. These are also required to register branded horses coming off the range so their DNA can be kept on file to match up with their potential future offspring. The second DNA test, and the type that this post will focus on, is the Coat Color Test. This is an optional test that you can select when doing parentage testing, or you can have them done through UC Davis & Texas A&M on your own. (Though please note that Texas A&M does NOT offer Dun testing).

So what is a color test and why bother paying for it?

Knowing your horses color genetics gives you a more accurate estimate on what color their offspring will be. This may or may not matter to you as an owner or breeder, but if you are buying breeding stock, it can sometimes be nice to know what colors they can pass on. Color testing is done in the same way as parentage testing, by sending in a hair sample to the lab.

So you get your test back and it's just a bunch of letters... what does it mean? EeAaDd ....EEAADD..... eeaadd!?

This is the part that I wanted to help with. I will only cover the 3 tests done for Kiger colors to keep things simple.

Horses come in 3 base colors - Red, Black & Bay

The genetics that represent these colors are a combination of Extension (E) and Agouti (A). Each horse will have one copy of E and A from each parent. Extension allows the horse to produce black pigment. Agouti controls where that black pigment is located (over the whole body *black horse* or just on legs, mane and tail *bay horse*)

Capital letters means the gene appears in the animal and is often passed to the offspring (dominant). Small letters mean the gene does not appear in the animal (recessive).

A horse with Ee or EE = can create black pigment

A horse with ee = no black pigment so the body is red. A horse with Aa or AA = black pigment is restricted to the legs & hair

A horse with aa = black pigment is not restricted Now lets put these two genes together and keep in mind - black is dominant over red.

Ee or EE + Aa or AA = Bay Ee or EE + aa = Black ee + Aa or AA or aa = Red (Agouti has no control if Extension is not present)

On top of this, many Kigers carry the Dun gene, which modifies the base coat by lightening the body and adding those beautiful stripes that we all love. There are 3 basic duns in Kigers - Red Dun, Grulla (black dun) & Dun (regular dun / bay dun). Any horse that carries even one copy of D will appear as dun - so the only way to get a dun foal is to have at least one dun parent. Lets put all 3 tests together... Ee or EE + Aa or AA + Dd or DD = Dun

Ee or EE + aa + Dd or DD = Grulla

ee + Aa or AA or aa + Dd or DD = Red Dun

Ee or EE + Aa or AA + dd = Bay

Ee or EE + aa + dd = Black

ee + Aa or AA or aa + dd = Red

There are many shades within these colors, especially grulla, which can be extremely light to very dark, but genetically they are same. Color genetics can be fascinating and complicated when you get into coat patterns, as there is still much that we don't know about certain traits.

One last note. There are also mutations of Dun called ND1 & ND2. The ND1 mutation causes the dun gene to be partially functioning. This creates zebra and dorsal stripes but does not dilute the base coat, so your horse may appear completely black or bay but still have visible stripes when the sun shines on him. A horse with D/ND1 will still be Dun but a horse with d/ND1 or ND1/ND1 will have this darker coat - generally these horses are not considered to be true dun.

Pictured below is a copy of the color test for the horse on the right.

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