training pens do not make them aggressive. train them on big hogs they are fear less dogs . train them to stop the hog as soon as the hog breaks. so the hog never get out the Bubble from the dog . to me{bubble} means train them to stop hog from drifting. traning pens dont hurt jagds on the hunting side they can do both very well.
a training pen is a nice tool when used right...but starting gritty pups to catch shoats in a pen will give them too much confidence and when they encounter a boar in the woods it could be there last...like already mentioned, the pup needs to learn how to bay a big hog and that includes how to stop one and keeping it from running...some folks don't like the bay pen but I think it is a great tool...what you want is to have the pup learn how to work the hog without getting itself hurt...but I am sure there will be some terriers that will be mostly catch...
