the bull is usually american or long legged staff and from fighting line of dogs it gives the lurcher more tanacity biting power and a massive pain barrier these dogs never seem to give up and when bull is intruduced to any lurcher it seems to give them that little bit extra go, ive seen 12 different dogs/bitches work they have all been self entering at about 10 months and grew to very good lurchers on all quarry, i was put of them for years as i was told they were thick as shit but I've yet to see a stupid one. The first one i saw was 12 years ago, i bought one 2 years ago and have never look