This is not my horse, but the horse that is next door to mine in the barn. I know hes older, I beleive she said in his 20's. His manure is so dark, almost black. She, (the BO) told me when the vet was out this week, he commented on the manure, saying it was too dark, didnt give her a reason that she recalled. I am just curious what would cause that and if its a sign of any problems going on inside??? Hes on the thin side too. Also, her vet said that it is VERY important for horses to have yeast in their diets to help with the digestive system. I never heard that before, but then again, i've never been so involved with equine nutrition till this past year when I got my horse back.