This will keep them off the permanent fences. Remember big charges aren't necessary for sows. They can't eat that much. Sows are the best place to start on grazing. The better the pasture the less the digging.
Alfalfa works well.
Chichory also works well. Baby pigs never get shots. Sometime only 2 days. I farrow in 6'x6' farrowing huts. Thats a sure disaster waiting to happen.