I have a large Mastiff that is certainly a deterrent. I almost had to get rid of her because of her aggression towards the other dogs, but I figured a way to keep them separated.
The way I figure, she is very loyal and very protective of the homestead, so she is worth having around, but if it ever gets so bad that I can't feed her, then I will probably be pretty hungry myself, so I can always eat her. She has a lot of meat on her, so I consider her both protector and livestock. It's a win-win. If I eat her, neither of us will be starving anymore.
The way I figure, she is very loyal and very protective of the homestead, so she is worth having around, but if it ever gets so bad that I can't feed her, then I will probably be pretty hungry myself, so I can always eat her. She has a lot of meat on her, so I consider her both protector and livestock. It's a win-win. If I eat her, neither of us will be starving anymore.