After a lot of research, I have started feeding our litters these raw meat nibbles and patties by Answers Pet Food and here's why....
Scientists are just beginning to learn the importance of the gut microbiome! Early studies are showing that a robust microbiome is synonymous with a healthier life. There is also evidence that, at least humans, have an early window (during infancy/early childhood) where population of the gut microbiome can have even greater long term effects. So in case that is proves true and applies to dogs as well, I've added in these nibbles by Answers Pet Food to our puppies' diet. Along with the raw meats/organs, they contain various ground fermented vegetables and kefir. I am also adding whole food sources of prebiotics to their daily diet, like mashed banana, pumpkin, white potato, rice, etc.
Don't worry, they will be come home on traditional kibble, but I feel like if there is anything I can do to help set our puppies up for a healthy life, it's my duty as a breeder to try it!
Worst case - I'm spending a lot of $ on real whole foods that they love!