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Differences in Roan Expression

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Raikit
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Differences in Roan Expression

Postby Raikit » January 13th, 2020, 5:18 pm

Hello everyone! I've had tons of roan in my Vlad lines for a really long time - basically since they were started - and wanted to share with you some of the interesting differences I've found in its expression.


Intensity

Roan, just like dun or flaxen, has variation in how intensely it is expressed. For example, these two horses have the same base color (except for flaxen and a minimally darker shade on the stud) but have an incredible difference in body coloration due to the difference in the intensity in their roaning.






A third horse with a similar roan expression to the second horse above, but on a brighter base coat:



Intensity is heritable - the parents will pass down their roan expression to their foals. From what I have seen intensity is not a gradation gene - it is dissimilar to leopard and tobiano in that it is not a matter of collecting "intense" alleles to continue adding to the expression, but seems instead to be a simple switch. If the horse has the gene for intense roaning then their expression will be more intense, if not it will be less so. It is possible that intensity is related to zygosity - it is possible that being homozygous dominant for roan leads to a more intense roan expression than being heterozygous. However I have not yet had a chance to test this.


Foal Coats

Roan intensity can be seen at birth. Some foals (like the first below) are easily identifiable as roan while others (like the second) are much more difficult to detect. Some roan foals may appear dun at birth. However, close inspection of foal coat (by zooming in) should be able to detect white specs on any roan foal that is not a double dilute.

Image
Image

As stated above, roan can be particularly difficult to detect on a diluted foal. Foal detection on double (or greater) dilutes is particularly difficult and may sometimes be impossible. Detection at one year of age is more reliable, though some horses may need to be tested through breeding to be confirmed.

A silver buckskin roan mare that was particularly difficult to detect as a newborn:
Image



A cremello stallion that is exceedingly difficult to detect, even as an adult. His giveaway is the light area on his cheek:
Image



A Classic Silver Pearl Roan (black + silver + champagne + roan + 2x pearl) mare that is impossible to detect roan on, but is proven to have the roan gene through her roan foal from a non-roan sire.
Mare:


Foal:


Sire:




Roan and Dun

Roan and dun interact in very interesting ways. Dun itself does not affect the intensity of the roan but the coat color will vary depending on dun's affect on the base. Intense roan can also mask some effects of dun that may be more subtly expressed, such as face masking and leg bars.

Black with intense roaning, no dun:
ImageImageImage

Black with intense roaning and subtle dun (masking but no leg bars):
ImageImageImage

A very subtle difference. And here are the horses side-by-side. The second one has dun, the first does not. The roan expression on the two horses is almost equivalent, but the second horse has a much lighter body shade due to the effect of dun.
Image
Image

Here is a third horse with roan and dun. This time the roan expression is slightly more subtle and dun expression is more intense, showing leg bars and more visible ankle spots:

Last edited by Raikit on January 18th, 2020, 12:37 am, edited 1 time in total.

StellaSim
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Re: Differences in Roan Expression

Postby StellaSim » January 13th, 2020, 10:08 pm

Raikit wrote:Hello everyone! I've had tons of roan in my Vlad lines for a really long time - basically since they were started - and wanted to share with you some of the interesting differences I've found in its expression.


Thank you for the post! Very informative, I love roans. I had roans running wild in my herd for a while, although they seam to have given way to cryptic duns now :P

BlackOak2
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Re: Differences in Roan Expression

Postby BlackOak2 » January 14th, 2020, 2:24 pm

I agree, nicely done!
And thank you.
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Raikit
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Joined: December 22nd, 2015, 9:49 pm
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Re: Differences in Roan Expression

Postby Raikit » January 18th, 2020, 12:38 am

Added a roan mare that doesn't look like she has roan. :)




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