
Unless I had a picky bitch who was eating poorly in whelp, then I have found using higher protein and fat feed (basically that is what puppy food is) to be counter productive and cause digestive upset.
Feeding more of a good quality food, and not increasing it until week 6 and only be feeding about half as muych again as normal by end of pregnancy has been the best for a fit bitch at whelping.
Once pups are born I am inclined to feed the bitch as much as she wants after the first few days.