I never really was told when we should switch food. We got Cincy when Sadie almost a year old, so we left Sadie on the puppy food. We had Sadie on large breed forumula at the time and the bag said to keep them on it til they were 18 mos. old. Cincy couldn't handle chicken products, so they both went to puppy lamb and rice. I don't remember exactly how old they each were when I switched them over, but I would say Cincy was about 7 mos and Sadie anout 18 mos. I don't know if it had anything to do with the timing of switiching or not, but Sadie is super skinny and Cincy is a little hunk-a-chunk. Personally, I think it is more the genetics (Sadie is Lab/Dalmation, built like a Dal and Cincy is lab/beagle and built stockier) and appetite.(Cincy will steal Sadie's food if she walks away from it for too long!)

Like you said,I would ask your vet or a breeder. They will have a better answer specific your dog.