I know that we typically do not do this stateside, but in Germany, S.V. rules dictate that if a litter contains more than eight (8) whelps, then the "extra" puppies must be nursed on a foster dam. The local breed warden is required to be aware of where these dams are located, and of course the breed of dam is not important.
I don't think this is such a problem until the puppies attain three (3) weeks of age. At that end they can quickly nurse the dam dry. I have endured a couple of occassions when it would have been very nice to pawn two (2) or three (3) puppies off to a foster dam.