Bullock is another word for a steer or a young bull. Most bullocks are raised for meat production, although some farmers have been known to keep their favorite bullock as a pet.
Bullocks are essentially young male cows, and the term usually refers to animals that have been castrated. The terminology varies a lot, though, so while some farmers and ranchers use bullock to mean "young bull," others use it to describe a youthful ox. While cows can be useful as dairy animals, bullocks are generally fattened and sold for beef.