As far as I know all the Fromm flavours are an all stages food, and interchangeable between other flavours without the need for transitioning, but I'm not 100% positive if that includes the Puppy food as well. Which brand of food are you feeding Bogart now? How old is Bogart? I switched my 2 from Royal Canin to Fromms Beef Fritata, when they were 7 months old, I had to transition them slowly. Hopefully someone with more knowledge or experience will come along and offer more advice.