Bulls can be trained to pull a wagon, but steers (that is, castrated males) are preferred, largely because they grow larger and stronger. . . .
“Because he has longer legs and he’s taller, an ox can travel much faster than a bull. Also,” Ford continues, “even though the bull may have a big burst of energy, like for fighting—because of its testosterone—, a steer would have more total muscle. So although a bull could easily kill any steer [in a fight], in working, the steer will have enduring power that lasts all day long, whereas the bull’s energy quickly burns up, and then he’s completely depleted.”