I have used electric fencing for year, the mains type as I was constantly forget to charge the battery type.
All I used for my Toggs is 1 strand of electric wire anchored on each post, this also stops them from standing on the stock fence.
Earlier this year when we were not able to finish fencing a section of field, all there was in place was the posts with 3 strands of wire, this was enough to stop them getting through.
I hate to say this because it is tempting fate, but I don't have any escapees or stuck heads
Hope this helps