I don't know a whole lot about horses or horse foods so forgive me if these are stupid questions. Are grain mites in ALL horse food? And are they bad? Can they hurt a horse if they eat them? I work at a pet food store and we have had some Strategy horse feed come in covered in grain mites. I looked into it and apparently Purina is having lots of grain mite problems. One of the managers at the store said that they were harmless and that they were in all horse foods. I have trouble believing that they are completely harmless and that its okay for horses to eat them. If this is a dumb question I'm sorry, but I could not find any answers in Googling this.