what’s slightly overweight? 20lbs? 30? Something that is easily fixed with working him for 15-20 minutes daily?
It would be better to muzzle, then to pull him off pasture for 6+ hours a day. Since once he goes back out, he’s just going to eat the same amount of grass, if not more, as if he was out for 24 hours.
Also, is he just on pasture or is he getting grain or hay as well?
If he’s getting either, I would cut him back on his grain. Maybe only give him a scoop if he’s getting supplements, if he’s not getting any supplements, take him off it completely or put him on a low starch grain if you want to give him something.
If he’s getting hay on top of being out to pasture, ask them to not give him any hay. This will help cut out calories and help him lose weight as well.
We had a similar situation at our barn, we couldn’t figure out why my moms horse was suddenly gaining weight. Then we found out he was getting hay on top of being out to pasture 24 hours. The barn owners would pull him for 6+ hours a day and then we’d let him out in the evenings, only for him to gain more weight because he was constantly eating. While when he’s out all day he comes and goes with the other boys. Not only was he getting fat, but he was getting a serious attitude and would sometimes swell up because he wasn’t out running and walking the pasture.
you need to do what’s best for your horse. I would first try to eliminate any EXTRA’s and then move onto the muzzle.
"Take the time it takes, so that it takes less time."
"Expect a lot, accept a little, reward often."