Ordinarily, an animal that kills a person will be put to death. According to the Mishna (39a) shor ha-itztadin – a “stadium ox” (i.e. a bull that was trained to fight) will not be killed if it killed a person, since the passage that teaches that law indicates that the animal will be killed if it gores, not if it was instigated by others to gore (see Shemot 21:28).
The Gemara on our daf asks about such an animal’s status with regard to other laws. For example, ordinarily an animal that has killed cannot be brought as a sacrifice. Would an animal like this be appropriate to bring as a korban? In response to this question we find that Rav believes that the animal was anoos – what happened was beyond its control, so it would not be held responsible and could be used as a korban. Shmuel disagrees arguing that the animal had committed a grievous sin, even if it could not technically be held responsible, it still would not be appropriate for the altar.
In his Nahalat Moshe, Rav Azriel Moshe Rothstein suggests that the argument between Rav and Shmuel is part of a larger question of how we must view situations of ones – of a forbidden act that one is forced to commit against his will. According to Rav’s approach, Jewish law separates such an act from the individual who did it, so we view the anoos not only as being free from punishment, but as if he did not do the act at all. Shmuel believes that the individual may be free from punishment, but we still view him as being the one who performed this act.
In the time of the Mishna, Roman stadia included performances of barbarism, including animals that were raised specifically for fights. Additionally (as is the case with bullfighting today), the animals were prodded and even stabbed in order to encourage them to gore and to attack.