spot on, you have to keep a eye on things. Its ok the older dog putting the pup in its place great. But when they get to 12- 20months , there is strong chance it will try to be top dog, and as above bull breeds can just kick off very quick. I used to keep bullmastiffs years ago, and they could be fine 90% of the time, then in second Bang all hell breaks loose, feck knows why.???? . Any dogs can start, so always let them know you are top dog, more so if you have dogs with bull in them, even though they might not start it, but will try to finish it,