Sorry if this has already been covered. When working with a horse rescue organization on the island of Maui we used miles and miles of electric tape and dealt with the wisest horses who could get through them. We found that the wider tape with copper strands was the most powerful. Delivered quite a zap. Also it pays to buy the hottest battery you can find. This is the most foolproof way we found. As I recall rebar was set at 10-15 feet intervals. All brush has to cut and the tape can't touch anything at all.
Hope this helps a little
Kathleen