I put down both my great Danes about a month ago. They were 3 and very co-dependant. One was ready to kill anything at anytime. My neighbor's wife is pregnant so with a soon to be toddler around, we didn't feel it was a safe situation. Nobody wants a 2 big dogs that can't be around children (they never did anything to person. we just didn't trust one of them) or other animals.
I live on close to 100 acres with hard woods, pines, and a thick field mix so i don't have to worry about that. Before the field got so grown up we used to run beagles had 9 of them lol.