Don't you think there is a difference though? All dogs have hunting instincts. Cindy will chase any rabbit or rat that comes in her yard. She won't bite heads off of them or attack me if I check her though. She would run at the first time someone yelled at her. It's hard for me to explain but it's like they just want to kill vs hunting. Very aggressive animals.
Oh - I don't trust the mind of a pit bull farther than I can throw the animal. They are different.
But chicken killing is not what makes them different... A temperament that was bred to fight to the death without quitting, is what makes them different.
I'm just speaking to most folks and the family labrador. If it's any kind of labrador, it's gonna kill chickens unless you invest a lot of energy changing it's mind. ;~D It's not illness, but instinct.