A friend changes halter types on her stud when she uses him for breeding and he knows what that means.
We don't because our stud 1)is easy and well behaved no matter what (he's older and totally different kind of mind) and 2) Bob is a firm believer that he better stay that way and just because he's being used for breeding he doesn't have a pass to behave like an idiot.
He uses a chain under his chin when breeding, but occasionally at other times also - especially when he's full of himself and hasn't had any exercise for awhile.
While breeding is the only time we use a chain on Rocky. He's very easy. It's more of a precaution to make sure he "stays' easy.
We learned that from one time, it was actually when I bred my mare the first time. It had been like 3 years since he had bred a mare. The first time we were leading him to her, he knew what was fixing to take place...only time I've seen him loose control, and we didn't have a chain on him. He reared up about 20 feet from her, pawing the air...it was a pretty awsome scary sight. The poor mare thought so too, and tried to take off. It was her first time.
Luckily Mack did manage to hand on to him and to circle him away, I went and found a chain and we've used it ever since.
Becky