I'm sure a vet could, but I would think you could check this yourself with a friend if your horse is the type to hear you preparing his food/packet of polos. I know ours can hear the key in the back door which signals return from school, because my daughter and friend snuck quietly round the side of the house and could see our 2 in the field, but they didn't move until they heard me put the key in the back door which was at least 400m away, so nothing wrong with their hearing!
