Why do farmers use barbed wire?

Barbed wire is a good type of wire to keep their livestock, particularly cattle and sheep, in. Barbed wire makes it a bit more difficult for an animal to escape because of the sharp barbs on the wire that cut into the skin. However, some animals are less prone to this than others, and some even find the barbs as a great place to scratch an itch they can't reach with their rough tongues.