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I had field fence with a hot wire top and bottom. Then I got a steer that would ignore the hot wire and fence. He paid attention when I electrified a strand of barbed wire. Hot barbed wire is the way to go from my experience and is pretty cheap.
My neighbor has 5 acres that has 4 strands of hot wire to keep the coyotes away from the sheep and goats. Haven't seen a 'yote around in a long long time. They used to come in and take the babies at night but not anymore. I imagine if the bottom one was hot, that might work.
We have just under 10 acres and have been replacing all the stretched wire fencing with Gallagher Equifence. The fencing can be set with posts up to 50' apart with a couple stays in between, the first section was done this way, with three strands and a charger, kept our longhorn cattle contained with no problems.I have settled on a five strand with posts about 20' apart on average, depending on the layout. Doing the work myself, it is running about $4.00 - $5.00 per foot, but again, I am using double the reccomended posts, and they are the round, pressure treated wood posts vs the metal tee posts.
DO NOT electrify barbed wire! Critters can get tangled up in it, panic due to the shock and die. Very dangerous. If you go barbed wire go with a minimum or 5 strands and 12.5 gauge if you can get it or no less than 14. I have 5 strand 12.5 4 point barbed with stays between each post. I also run a heavy gauge hot wire 12" off the ground and another 2' up from that.