Each year, when the bucking bulls arrive at Madison Square Garden, livestock trailers pull into 33rd Street and back up to ramps that lead five floors up to the arena.

The bulls — 50 or so — come for the opening event in the Professional Bull Riders circuit, which this year runs Jan. 4-6. Cowboys on horses, letting loose an occasional whoop or holler, herd them up the ramps. The bulls soon emerge into a kind of animal-athlete locker room, with a dirt floor and strong steel bars arranged horizontally to form stalls.

Some bulls walk calmly into the mazelike corral. Some trot. Some come in hot, trying to charge the workers, who quickly climb the steel bars to get out of the way.

This is only the locker room, of course; the bulls don’t have to bed down at the arena. Once the event is over and the cowboys head to their hotel, the bulls are trucked back to more comfortable quarters in New Jersey for a restful night.