I've always fed from square bales so I don't know much about round bales.
What I've heard in the past and always believed was that you shouldn't feed round bales to horses.
I was told since they are so large and have to sit out for more than a day to be consumed, that the center of the bale will mold and cause horses to colic.
Is this a myth? Or perhaps it is OK to feed them in areas of the country where it is dry? I live in the Pacific Northwest where the ground is damp and it rains frequently.
Around here it is normal to feed round bales to cattle only and I don't actually know anyone who feeds round bales.