Hay can be a good cash crop but not if hogs have rooted it to Hell and beyond, so I sympathizes with your plight.
I realize that the hogs are destructive but hey, they can be killed and even exploited financially. Have you ever thought of putting out contraceptive-laced hog feed? Stopping the reproduction cycle while at the same time culling and/or rounding them up to sell for profit could go a long way towards eliminating the problem. Oh, and can electrified fences keep them out?
The problem we have here in southwest Washington State is coyotes. Oddly enough, something as simple as a decorative aluminum fence, the 7’ tall kind that look like a row of spears, actually keep out the coyotes plus deer won't jump the fence because of the points on the top.
They’re working both on contraceptives and plain-old poison, but the problem is that anything put out for the hogs also endangers good wildlife and livestock.
Nothing stops them easily. There are no natural barriers, and they do not honor fences. It would be impractical and impossible to fence them out with electric fences. They range for miles, the cost would be prohibitive, and they’d just rip through the wire.
Right now the most effective method of control — which is basically just keeping the population from growing — is aggressive hunting and luring them into pens with feed. But penned feral hogs are fierce creatures; it takes a trained tough-guy team to handle them. They will attack, and the big ones have nasty tusks. There are men who make money capturing the creatures and transporting them to processors, but that’s tough work.
We have plenty of Texas coyotes, but I can’t imagine one taking on a wild boar.
One bright side is that the meat of a healthy hog is very, very tasty.