What's a Schweinehund, really?

Something I must have seen in the last few days caused the term “Schweinehund” to pop into my head. It started bothering me. My German dictionary translates it as “bastard”, just an ordinary, everyday term of abuse, or maybe a convenient and funny oath for old “Hogan’s Heroes” programs. However, I realized that by analogy, there might be “pig dogs”, just as there are “sheep dogs” or “cattle dogs”, in which case the word has a a different sense. Could “pig dogs” have been common enough to give rise to a term? My American Heritage dictionary does not show the term in English, though it does show “sheep dog”. It would only make sense if herds (flocks?) of swine were allowed to wander and forage, and some means of controlling them was needed, short of the swineherd running around trying to corner the strays. Is there a breed of dog called “Schweinehund”, either AKC or colloquially recognized? My book of dog breeds doesn’t mention one. Any ideas, anyone?

It is truly an insult. pig dog is literal, dog that lies with pigs is inferred. Crossbreeding is looked down upon in Germany. Some Germans, (Please, do not flame me) possibly used to think of human differences as a species thing. I have only heard this, or read it in older books.