John, good disposition is a must on any bull I use. I leave the bulls in with the cows and calves from bull-in day to weaning and with the cows after weaning until about January 1. So when rotating intensively, I'm often in the pasture with the group in close quarters and don't want an aggressive bull or cows that I have to be concerned about charging me or getting the others riled up. 

Rotational grazing is much easier with a bunch of mellow cows and a bull that defers to me. Whatever cross bulls I end up using will be checked out for attitude #1.

That brings up the question about AI bulls and disposition. Is it assumed an AI bull has a mellow disposition just from the collection process? I would hate to have a bunch of high strung calves from an AI bull no matter how good his other EPD's are. That may be another reason to stay with a walking around bull rather than one in a straw?

Jim at Dawn