My lab/husky was 3 when I got my flock. He and the chickens shared half an acre (with the chickens having exclusive access to another half acre which we kept him out of due to the conditon of the fence and his tendancy to wander) He has no prey drive at all, unless something threatens HIS flock of chickens or his kids, or his cat... He is so docile, its amazing that he has rescued a hen from a raccoon 5 times (same hen, same coon). Fool bird has no idea she owes her life to him. I gave up getting up to check on the birds in the middle of the night when I heard squawking. he was so much more effective, I just let him take care of them.
My puppy (ok, so at 85 lbs and 4 years I suppose 'puppy' isn't quite accurate) being an only dog got so attatched to his chickens that he has actually tried to become a vegetarian! I kid you not. He used to inhale any meat based kitchen scrap he could find, but since the day he found out where chicken comes from (we proccessed an agressive roo who went after the kids... the dog was so upset!) he WILL NOT EAT raw poultry of any kind. He won't even taste it... he just looks at it, sniffs it, and looks at me with big sad eyes like he wants to ask why the poor birdie had to die. Of course they smell different cooked, and he hasn't made the connection yet, but he has done his best to give up poultry. For my darling dog, chickens are definatly friends, not food.