Actually any breed of dog which is easy to take care of and loyal can be used as a guard dog nomatter what breed it is. My previous post is searched from the net as you asked what breed is the best guard dog... I got a friend which picked up several mongrels from animal welfare societies to use as guard dogs for his factory and it turns out pretty well too! It proved that mutts can also be as good as pure breds right? You can find some larger sized dogs, no matter what breed, as you've witten that you wanted to protect your farm from wild boars or other wild animals. Normally dogs won't simply ran away as most of them attached to their owners and homes... Some of them can even be let free without running away!