The type of dog food makes all the difference. That premium stuff you used was no doubt excellent for dogs, but as you discovered, a killer food for rats, too high in protein. My females average 12-16+ pups per litter and I have been using cheap low protein dog food as a base food source for 5 years and never had any problems.
I do supplement with table scraps such as chicken and meat bones and have discovered that rats love mouse pinkies, fuzzies and hoppers. Any left over mice on snake feeding day goes to the rats and not the trash can. That is their only additional source of protein.