How often to you check your cattle? Just wondering if he was acting punky the last few days or if there had been any previous signs of illness. Agreed, it seems unlikely about the bulls. Do you vaccinate for Blackleg? No vaccine is a guarantee but Blackleg is generally discovered by finding a dead calf. Also, did you check in his mouth to see if he may have something stuck, causing him to asphyxiate? Had you banded or castrated him recently? Could be tetanus. Bottom line - there is no easy answer unless you have a vet perform an autopsy or examine tissue samples. Sorry for your loss!