Hi! I am not a food expert..but I'm sure those more knowledgable people will chime in soon. My vet puts her Bully pups (and she has a lot in her practice) on all stage food as early as 10 weeks. Even sooner if they come home on a crappy food
like Iams..like my Jake did. She has all ages of Bullys in her practice and she is a pretty conservative vet. I agree with a slow change whenever you must switch. Sometimes you have to kiss a lot of frogs before you ind the correct food for your individual dog...I don't think careful switches done for the right reasons will hurt your dog..in my opinion!