Electric fencing is highly effective with pigs. Pigs, like all species, need to be trained to electric fence because it is a psychological barrier. Unfortunately you have trained them that they can brave the fence and bust out. Retraining them will be harder. To train them put them in a physically well fenced space of about 250 to 1,000 sq-ft. Put an electric fence inside of that just like you'll have out in the fields. e.g., step in posts with polywire or what ever. In about a week or two of training in this area they will be ready to venture out into well done electric fenced paddocks.
I would suggest three wires to start with although even a single wire will work for well trained pigs. Wires
should be at low and high walking nose levels. Third wire about 36". If you have jumpers, such as flying pigs or sheep, then another wire at 44" or so.
Tight wires are far better than loose wires. Highly visible fencing with a good visual marker (e.g., stone wall, brush, forest) outside the fence is helpful. Keep the things they need and want inside the fenced area and the scary things outside.
When a pig is shocked on the face in front of the ears it tends to go backward. When a pig is shocked behind the ears it tends to go forward. Strong tendency in both cases.
If you have a Houdini and can't retrain him, eat him. He is a bad influence on the other pigs and a waste of your time.
We keep about 400 pigs on about 70 acres using managed rotational grazing and many miles of electric fencing for our perimeter and paddock divisions. Properly done electric fence is highly effective for pigs. Here are some articles about how we do it:
http://www.google.com/search?q=site:sugarmtnfarm.com+fencing%20OR%20fence
Cheers,
-Walter
Sugar Mountain Farm
in Vermont