How teaser bull is prepared surgically?

There are two options. The first is a vasectomy, in which the vas deferens connecting the testes to the urethra are severed. The second is a penile diversion, in which the penis and prepuce are directed laterally to prevent entry into the female.

Both options have some risks of surgical complication and are not 100% guaranteed to prevent the teaser bull from being able to impregnate a cow.