I think that the pet breeding has pretty much shot 99.9% of great danes in america to number 2 as far as making them working dogs. Would take some time and some good culling to get a good working line going again.
I think Boarhound is just what danes were called before people started breeding them as pets. I have just called anything that will run down a hog and catch it a boar hound but here is a definition.
http://www.thefreedictionary.com/boarhound