Bucking Bulls

In rodeos, more specifically bullriding, how do they make the bulls buck so violently? I’ve heard that they use shockers but I’m not sure if that’s true or not.

Speculation from a city slicker:

I was told they tie the animal’s “nut” (with a rope or rubber band I guess); this puts the bull or bronco in a sour mood and makes him buck in an attempt to loosen the offending “constriction.”

Akk. His “nuts” not “nut”! By which I mean, of course, his scrotum/penis.

Yup. Tie a rope around his balls, with the knot on top of his back. When you see the guy pull the rope end as the bull heads out of the arena, he’s untying that knot.