I'm not sure that my horse had the same thing, but my own
horse had a dark "separtion" or indentation in the hoof wall after his upright
hoof was accidentally trimmed incorrectly. For awhile, it appeared that
hoof was foundering (coffin bone appeared to be rotated slightly on x-rays) and
he was lame on that foot, however, with proper shoeing, the situation appears to
have resolved.
I would think you might want to get x-rays and talk
it over with your vet and shoer.
While on the topic of hoof cracks, I have noticed
a spongy, soft, blackish "divet" at the coronary band and front hoof wall
of my gelding. Any ideas what this could be or have resulted from and if
it could affect soundness? It doesn't seem to be getting any better and
not sure if I should try to treat it in some way. Thanks.