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Dun Factor vs Countershading

My foal has stripes. Is it dun factor, or countershading?

Copyright and "Up to Date" Note:

Please note that all of the text information on this page was originally composed by me unless otherwise referenced, and was typed with great thought.  I have read books and many educational web sites to contribute to my knowledge base.  Some of the content was created in the late 1990's, and may need to be updated. With 300+ pages in this web site, I can't remember which pages need updates all the time. If you see an out-of-date page, let me know so I can update it.

Some photos were donated by people that have horses with color examples needed to provide educational content. For that reason, permission is not granted for anyone else to use photos from these pages.

Please feel free to link to this page, but do not copy the content and place it on your site.

"UP TO DATE" Note:  Some of the color/informational pages on my site have not been updated for a long time due to my lack of free time to do so. 
I am leaving the pages up because they are still helpful. BUT, some of the terminology is incorrect and there is also NEW knowledge available regarding color genetics. Some day, I will update these pages...when time allows.

Click here to learn more.

"Countershading" is a form of striping that is probably a remnant of primitive camouflage, but which is not the same as dun striping.  It is not a dilution, and is often only visible on young horses.

Some horses will retain some countershading for their whole lives, but it is far less distinct and contrasting with surrounding colors when compared to dun factor striping...usually. ;-)  2016 update:  UC Davis has information about possible genetic causes of stripes that are not dun factor. When you reach the bottom of this page, you'll get a little more information and a link about this.

There is often a great difficulty determining a horse's color when it comes to dilution genes, especially as foals.  Because of countershading, sooting, and other color modifications, foals are often mislabeled as duns or grullas when they really should be registered as buckskins or blacks.  See the bottom of www.grullablue.com/grullocolor.htm for photo examples of foal coat colors that can easily be mistaken for dun/grullo colors.

As horses shed their foals coats, it should become more readily apparent if they carry the dun factor trait or not.  Not always, but usually. Sometimes, a DNA test is the best action for an overly-anxious owner to determine actual color. If one does not want to spend the money to test, then time is often the answer...most horses will show their "true color" by the time they shed off their winter hair as a yearling.

The following photos are of horses that are NOT dun-factored horses. 

Examples of Countershading (NON-dun factor striping) Markings

Not Dun Factor
This bay foal has a good example of a countershading stripe.  There are NO duns in his background, so we know he is a bay with countershading.  Most likely, his stripe will disappear when he sheds off as a yearling.

Not Dun Factor
A black foal with countershading-caused dorsal and shoulder barring.
Click here for proof that this filly is not dun factored.

tuscarorastablesdotcom.jpg (7392 bytes)
Not Dun Factor
A black foal with countershading.

Not Dun Factor
DNA tested buckskin with NO dun factor gene.

Not Dun Factor
This foal is bay or bay roan, but has an amazing countershading stripe and shoulder patch that will disappear over time. He can not be a dun, as he does not have dun factor genetics behind him in the pedigree.

Not Dun Factor
Super pictures of buckskin foals with countershading stripes that are not caused by dun factor. Notice that the dorsal on these foals stops abruptly at the top of the tail. The foals also do not have ear tips.

Neither dun factor nor countershading.

These are not stripes. This is a hair pattern that shows up best on black and blue roan foals' back legs (and even hips), and that many people mistake for leg bars. It is not, and is probably a trick of lights on waved/curly hair.

Not Dun Factor

Countershading stripes on black and smokey black foals' legs are fairly common, but disappear over the first year.

Show What You Know!

The pictures below show examples of horses that may or may not have dun factor. Can you get the colors correct by looking at these pictures?

Interesting picture, below. It shows how hard it is to guess horse colors when you can't see "the whole picture" through multiple photos, seeing the horse in person, and/or knowing the sire/dam genetics.

Without looking anywhere else but at this photo, what colors do you think these two yearlings (below) are?

Click the photo above to enlarge it.
Photo will open in a new window.

Then click HERE to see if you got it right!

Click the photo to view it full sized.
3 dun factors, one countershading (non-dun).
Can you tell which is NOT a dun factor dorsal stripe?

2 dun factors and one non-dun striping. Which isn't a dun stripe?

Click here for the answer.


This mare has been DNA tested, and is BUCKSKIN, not dun or dunskin.
Her test results concluded that she does NOT have a dun factor gene. Her stripes are amazing, but are apparently caused by another factor (possibly nd1).
Despite having a dorsal stripe with shading on the side, some leg stripes, dark tips on the backs of the ears, and even faint cobwebbing on her forehead, she is not a dun nor dunskin! Thank you for the great pictures, Kirsty!

UC Davis Information about Dun and Non-Dun Stripes

Three variants in DNA sequence explain phenotypes (how horse "look" to the eye) related to Dun dilution:

  • D (presence of dun dilution and primitive markings)

  • nd1 (not Dun-diluted; primitive markings are present but expression is variable). Think of "nd" meaning "not dun."

  • nd2 (1,617 bp deletion, not Dun-diluted, primitive markings absent). Think of "nd" meaning "not dun."

  • With respect to variant interactions, D is dominant over nd1 and nd2; nd1 is dominant over nd2.

  • The VGL offers a DNA test that will provide information for both dun dilution and the primitive markings. Click here for more information.

This page last updated 05/07/16
If you notice this date being 2 years or older, please let us know that we need to check out this page!

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Toni Perdew       Bedford, Iowa
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