They can beller, blow snot in my face or breathe down my neck and I am fine, but the moment one of them starts actually threatening me she gets a black mark.  I want a mother with a strong protective instinct, but that still understands and never forgets that I am at the top of the pecking order.  If they threaten me beyond the bluster and bluffing I get rid of them.  I don't have the time or the inclination to tolerate cattle that will injure me because I work alone almost all of the time when I am calving.