No, not all the horses were like this. This is either the only rideable horse (the rest are unbroken colts) or he could be one of the three rideable horses in the whole place.
He is kept with 2 other horses and they look different from the other horses kept in different stables. The other horses (about 40) look well fed though and no ribs can be seen.
I'll upload another video of a second horse (one of those staying in the same area as the horse in the first video). Just need to get Youtube working.