I've wondered the same thing. Shiva and Kharma will be the first female dogs I've ever had bred, and I've been dreading that one, especially since there are things on a farm that they could conceivably snag those "sagging boobies" on!
I have noticed, though, that most dogs teats do reduce awhile after the pups are weaned. I don't know if there are any tricks to help, but I'd like to hear, too, if anyone knows any.
There are a few people here who breed, so maybe someone will give us some ideas?