We have never fed round bales much, mostly because 1) we don't have a tractor so cannot handle them easily and 2) it's actually very difficult to get GOOD round bales. We've tried some here & there over the years and more often and not the hay is not good in them. So many of the farmers bale the hay a bit too tough & it doesn't keep--they might be able to make good small squares, but the hay needs to be just a wee bit more dry to keep in a big round bale.
I have found 3 guys who make decent round bales. One I haven't actually bought any from yet but may this coming year. The other two...I did buy from this year. The rounds are so much cheaper than the small squares, and I had trouble getting small squares that weren't heavy alfalfa this year. I like to fork the hay out to the horses twice a day, so our bales were all put out in the side pasture last fall. That worked fine, except we now have 3+ feet of snow and so the round bales are very hard to dig out! I didn't put the bales out in the pastures because I thought the horses would waste too much if I just let them eat off the bales. However....
Some of the mares recently climbed over the fence (deep snow means fences are very low!) into the hay yard, so I opened the gate & let the rest of them out. That is 11 horses I no longer have to feed--and they are doing a fine job of getting hay off the bales. They've eaten one bale that I couldn't dig out of the snow, and are now on a 2nd bale that I'd given up on using. I cut the twines and pull off any of the outer portion that is spoiled, and then they eat from there. The bales are lying flat, not standing on end, so the hay doesn't fall off & scatter like it would if they were on end. They aren't wasting any more hay than they would if I were forking the hay out to them--I always give them plenty so they always leave some anyway. They aren't eating any more than they would if I were feeding them 2 times a day, since even that way they generally have hay available 24/7.
The spoiled hay that I pull off the bales (and that is left at the bottom of each bale) is just left out in the hay yard so far, but the mares leave that and go for the good hay. They've been chewing on some of the unopened bales, but just the ends, so that's not really a problem. Now that I see how much work this is saving me to have the mares out there getting their own feed....I'm kicking myself for putting all the hay out in the hay yard and not in the pastures!!
Next fall I will be putting a certain number of bales in each pasture, and then the majority of the horses will be able to feed themselves.
This year I had enough bales hauled in to last through to the end of March. In March I'll get some more brought in. The fellow I'm buying this hay from has the bales stored in a shed, so they're out of the elements there. When I get my spring supply it will be in good shape yet, with no weathering like it would have if I had the bales sitting here through the winter.
I wouldn't want to feed straight alfalfa this way, because some of the horses would surely eat too much of it, but this hay is a mixed grass/alfalfa. No one is gaining or losing weight, so all is good.