[anonymous]

Please consult your vet. It often takes 2 weeks to a month to determine if a food agrees with the dog or not.
If your dog is that sick that it cannot tolerate even a subtle change in diet I would discuss prescription/therapeutic diet with your vet, asap
Seriously…

PS: I have changed brands cold turkey, no transition, nothing. If the dog is healthy all you can expect is loose stools off and on for a week or two. Anything more indicates that there is something wrong with the dog.