I did a lot of research on foods when one of my babies got allergic to our Lamb and rice food... What I learned is that when you go from a commercial food to a more natural food, it may be hard for the dog at first because the more natural foods have less digestive aids in them. The commercial ones (like anything purina makes) have stool hardeners and stuff that makes the stool come out perfect.
When I switched my dogs to Solid Gold Wolf King, they said my dogs have to "detoxify" and their stools would be huge at first and loose and then go down slowly. It's been a month and a half and they're back to normal finally and I know it's not because of chemicals..
One of my dog takes about 5 days to switch while the other hugely sensitive big guy takes a little over 2 weeks (it's almost like you change 5 kibbles/day...).
It makes you wonder though, if the foods are full of hardeners and digestive aids, how sick does your dog have to be to produce loose stools?