We have a 225lb Duroc barrow that can barely stand on his back legs when he walks he almost drags them. He was fine yesterday our fair starts Saturday

Sounds like nerve damage. If it is muscle then I would suggest rubbing some kind of cream on there to loosen up the muscle. Being so close to the fair I am not sure of withdrawal times so you need to be careful if you give any kind of oral medication. I would keep him penned up until time to go to the fair. If he is not better by that time I would say stay home. You do not need to put a lame pig in a show. It is better to not show and be ethical than to try and show and make the pig walk when it cant and shouldn't.