A few years ago I lived in the foothills of the Sierra Nevada mountains above Fresno. As one person said, people would take their unwanted or unmanagable dogs to the hill and chased them off. I think most were killed by coyotes etc but some turned ferrel and lived in packs and became dangerous to people as well as live stock. They stalked hikers etc.
At the time I had about 6.5 acres which backed up to thousands of acres of hills. I had four horses plus to foals on the ground when someone told me that were dogs circling the foals. I took the first gun that was hand, an old 22 Sears bolt rifle and headed out to see what was happening. Sure enough, I went out to the pasture area and found two ferral dogs, 6-9 months old harrasing the horses. Their mother had made a den in a small cave on my place and these two survived, at least until that day.
I shot them each with one 22LR from about 40 yards and they fell dead where they were hit. The neighbor called the Sherrif and Animal Control both of whom told her that either feral or pet dogs can be shot if they harrasse live stock and that I was perfectly within my rights.
The whole scene was repeated a month later when my neigbors calves were attack by a beautiful Irish Setter and his buddy great dane which belonged to a guy that lived adjacent to his place. A 25-20 old lever gun took care of the pets. Sad to see them dead but losing a calf or two is losing serious money.