I can't tell if this is a serious comment or not, but if you're being serious this is horrible advice. Some dogs bites are strong enough to crush bones, and they aren't even 100 pounds. You want to willingly give them a limb so they can actually snap it in half?

Sure, if you're fighting a 50 pound Australian Shepherd, have at it. If you're fighting a 150 pound German Shepherd, you're going to die.