There is a single strand of wire running along the fenceposts, and when it was electrified- It shocked the living piss out of every animal the touched it. After 3 months, the shepard was able to turn off the power to the fence, to save electricity. We do the same thing here in the south. When they see those yellow insulators and that strand of sire shocking a horse or cow for 30 minutes before they are freed- the herd gets the message. If one breaks out- most are still to terrified to leave, as long as they are well fed and watered and feel protected in their cages.