Pumpkin's babies where 3 days old when my vet called and asked if Pumpkin could foster some puppies, their mother had just died of a large tumor.  Pumpkin is the Holstein of the dog world she makes so much milk she leaks. There were 7 little golden retriever puppies. They were born the same day. Pumpkin nursed the whole litter as the poor little things hadn't had a meal all day do to mum's illness. Then they left 4 with us. The other 3 went to a golden breeder who had a litter of 7 which was 4 days older.  We had the golden pups until they were 4 weeks old and weaned.  Pumpkin was a wonderful mother, at first she would not clean the goldens only her own, I tried to rub food on them but she was smarter then me.  She would clean her's and skip the orphans.  I think she could smell their mother and it took about 4 days for her milk to go through them and then she was fine.  When all the puppies were reunited Pumpkin's 4 where very much bigger, the lady with the other 3 asked my vet how come my 4 where so much bigger-- the answer: Swiss milk.