What genes cause brown manes/tails?

[AAHunterGal]

I’ve just bought a young OTTB who is bay with a brownish mane/tail. It could also be a little sun bleached, but his sire has the same traits.

Pics are attached (the one who looks younger/not like a stallion is mine).

Is there a gene that causes this to happen in an otherwise bay horse? I’ve tried to google and can’t find anything.

[Jackie_Cochran]

You might find something similar if you google “wild bay”.

I once mistook a bay at the riding stable for a chestnut. My riding teacher pointed out his black points–lower legs.

Trying to figure out why this horse’s color fooled me led to me looking at a lot of pictures of bays. “Wild bay” was what matched, sort of. TBs have this particular color too.

I really like your new horse!

[Scribbler]

Black can also fade due to mineral deficiency

[AAHunterGal]

True, but I know neither horses are black or mineral deficient.

[jvanrens]

Black comes in different shades just like any other colour. I think that is what you are seeing here.

[endlessclimb]

My mare has this in her tail. Her sire does too (Honor Code).

She’s on a ton of Cu and Zn so I can’t get her any darker, and still the side floofs of her tail look sun-bleached-brown, and the very tippy tips of her mane.

[JB]

@AAHunterGal

I know neither horses are black or mineral deficient.

You can’t know mineral status All you can do is know the diet is providing at least the min requirements, and you can supplement to see what level of fading reduction you get, which may be a decent bit more than the basic RDA of copper and zinc.

But when there’s nd1 in the picture, the horse will fade, period. nd1/nd1 fades even more. And nd1 is present in a ton of breeds, even the ones that don’t have D (dun), like the TB.

The OP horse is (clearly) bay (so no need to test for bay vs chestnut)

Wild bay and brown are 2 phenotypes of what is only testable as bay. Bay can be from a very light bay, to “looks black until you put him next to a real black” shade.

And, there are also simply shades of black, even among black horses, so manes and tails of bays can vary in shade as well

[Nootka]

If he was color tested, he is probably ND1 (not dun1) it is known to cause the fading that you see.

Dun Dilution | Veterinary Genetics Laboratory (ucdavis.edu)