Adult bulls may weigh between 500 and 1,000 kilograms (1,100 and 2,200 lb). Most are capable of aggressive behavior and require careful handling to ensure safety of humans and other animals. Those of dairy breeds may be more prone to aggression, while beef breeds are somewhat less aggressive, though beef breeds such as the Spanish Fighting Bull and related animals are also noted for aggressive tendencies, which are further encouraged by selective breeding.
It is estimated that 42% of all livestock-related fatalities in Canada are a result of bull attacks, and fewer than one in twenty victims of a bull attack survives.
Dairy breed bulls are particularly dangerous and unpredictable; the hazards of bull handling are a significant cause of injury and death for dairy farmers in some parts of the United States.
The need to move a bull in and out of its pen to cover cows exposes the handler to serious jeopardy of life and limb. Being trampled, jammed against a wall or gored by a bull was one of the most frequent causes of death in the dairy industry before 1940.
As suggested in one popular farming magazine, "Handle [the bull] with a staff and take no chances. The gentle bull, not the vicious one, most often kills or maims his keeper".