Our minis have the same management as our riding horse, meaning, they are out from 6/7 am till about 5/6 pm, then in a stone dust paddock overnight (no muzzles, of course, and with night hay feeding).
In the growing season, they spend basically the entire pasture time in a muzzle, though I often leave them the first hour for grazing without.
I can do that, because they are two and they play rough with each other (so they do burn some calories).
When we only had one mini, he was in a muzzle the entire pasture time.
Our riding horse is very kind, does not play rough, and they all seem to enjoy each other. I know, there is a risk involved with combining the big and the little ones, but I am willing to take it, considering the temperaments of animals involved.
What I like about the pasture turnout is that they get to travel, investigate, and be a herd. I think, it is more stimulating that sitting in a paddock all day. I think, they need the stimulation.
I make sure, muzzles are well adjusted and clean them daily.
I give everyone treats through the hole, when putting the muzzles on.
Our horses tried to escape muzzles (after initial first day of put-on) for only a couple of days. I would make time to just calmly walk them down and put it on. No punishment for escaping and treat through the hole.
We have been using muzzles for a couple of years now and everyone just accepts it as a matter of fact. They seem to look forward to the treats.
We generally muzzle March- December (minis). Normally, we don’t need muzzles for January and February at all.
Last year, when winter was harsh, minis had their time off for about three and half months. They loved it.