You won't do any harm by adding a cup full per day. A neighbour of
mine swore by it. She has a 28 year old stallion who suffered from
arthritis until she started using it a couple of years ago. Now he
doesn't suffer any more - although she does notice it if he goes
without it for a week if she's not had time to restock. If it doesn't
work though, you won't be hurting the horse. They seem to like it,
once they get used to it. Start by adding only a little on the
first couple of days. This is starting to get a bit 3rd generation,
but according to the neighbour, another friend did a test by
introducing the acv, then one day offered half the feed with acv and
half without - all the horses ate the acv one first.
Jo Brock
Adelaide, Australia