I've had 2 foals born with a "blond" spot. One is a bay Arabian mare and the other is a chestnut Half Arabian. No relation to each other. The bay had no white markings, but chestnut has 4 stockings and white down his face.
The bay is 11 now and has not lost it, the chestnut is coming 2 so has shed a couple times... so it's there to stay also.
I would only think deficiency if it is a new spot or only showed up not too long ago. If the horse has had it for a long time I would think it is something genetic. My horse has a roan spot on his neck, he was born with it and it has dark skin under it so it is not a white marking. Some horses just have cool markings.
due to copper deficiency are pretty well documented in cattle, less so in horses.
If it is a low Cu problem it's an easy fix. Low Cu is not without effects, if it continues will eventually lead to more profound problems.
If the spots are genetic then the Cu supplementation will not change them.
Supplementing with Cu is an easy and inexpensive way to find out and might save problems further down the road.
Melyni (PhD) PAS, Dipl. ACAN.
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Thanks everyone. It's not a roan patch, it's just solid color. Although the little patch by his hip is a white spot that I assume he got from some kind of past wound. I'm just curious because I saw another horse with a very similar patch and I just could not figure it out.
JB, could you explain the somatic mutation a little bit more in layman's terms? I've been looking it up but most of what I'm finding is going over my head
The horse might be a chimera (I think that is what JB is getting at) where the animal is actually a "blend" of two fertilized eggs that fused together very, very early in the process of embryogenesis. So the resulting critter actually is a blend of two genetically slightly different cell populations. I think it can also be a spontaneous mutation in some of the chromosomes rather than a necessary fusion of zygotes/fertilized eggs. Lots of ways it can happen, and it's rare because if anything goes even slightly wrong in this process, the embryo is usually unable to survive. I'm pretty sure brindle horses are due to chimerism, but am not sure why they would have "stripes" where another type of chimera might have "spots".
It can be caused by a trapped nerve. The pain makes the horse sweat excessively in a very localised area. The sweat then bleaches the coat when the sun gets on it.
Recommend a visit from a physio.
Oh for criminies sakes. I have seen this coloration in newborns, sometimes on one lower leg , and on horses who never had a drop of abnormal sweat on the area. As well, I have had horses with isolated sweat spots due to nerve damage, ing and their coat never bleached out from it. It is GENETIC.