Which type of livestock operation can best benefit from having a guardian animal? I've heard a lot about them, but I've never known anyone who used them. It's strange that a herding dog can't perform both roles.
Any livestock that is in danger from predators can use guardian animals. I raised Goats, sheep and chickens and I had llamas as guardian animals. They worked great. There are breeds of dogs who are guardians and there are breeds of dogs who are herders, I don't know any breeds who do both.