Plenty of round bale feeders and all sorts of other equipment as marketed as "horse" but no-one with 2 ounces of common sense would actually use it for a horse.
Half the round bale feeders out there aren't actually *safe* for even cows IMO. I have a Hereford bull and a Hereford x Angus steer boarded at my place right now, their owner has a round bale feeder out there and I watch the poor bull get his horns stuck in the feeder at least twice a day. He always manages to get unstuck but he has bashed the feeder to heck and back doing so. I took the feeder out yesterday as he broke 2 of the 3 pins holding it together when he got stuck.... waiting on the owner to bring me replacement pins.
I prefer tire feeders, I have a cart for my ATV and I fork the hay into that, haul it over to the tire feeders and fill them up. More work but nobody can get hurt on a tire feeder and they hold enough hay for a few days (depending on size of tire and herd).