Stop putting them in a pen!! Unless you are wanting a bay pen dog. They have an interest in hogs wait til its time to go to the woods. Baying in a pen and baying in the woods are 2 different things, They learn to bay way too close in a pen and that will get them cut up or worse in the woods. IMO
X2
Start doing staged hunts with them. Drag you a hog around and tie it up in the bushes. Make them go find the hog. Start short and increase the distance. Once they get that down, hobble two legs and cut the hog loose.