My mother grew up on a sheep farm and told me a couple of stories about the sheep dogs going crazy for blood thirst.
It happened during the pitch black of night, in large sheep fields out in the country. All would be peaceful except for a strange bleating of the sheep. In the morning, the scene would be revealed, the sheep dog had gone wild for blood thirst and had chewed out the necks of a number of the flock.
At that point, the dog would have a taste for blood and could no longer be trusted to not repeat the slaughter. The farmer would have no choice but to put down the dog. A pretty big tragedy to the farmer, as someone who's livelihood relies on the work and health of these animals.
Anyways, I'm having lamb curry tonight.