Depends entirely on the individual dog. Boxers weren't a hunting breed so possibly less prey drive? We had a boxer growing up that would lay down and let the chicks crawl all over her.
As far as the quarantine issue being discussed, I think it's something people fret about too much. So many ways for illness to find its way to our flock, as long as the new bird appears healthy I usually don't bother with it. Of course we also live in a time where people medicate their sick chickens instead if culling then immediately, or at the least isolate them and see if they recover on their own. All that attitude does (the medicating and vaccinating) is make the genetic stock weaker.