First off, I think this is a topic in which even many vets are divided. But, we started adult food from the beginning. I don't really believe they
need puppy food, per se. And our breeder actually thinks the adult food helps "straighten" out the bones as they grow (per advice she received). I believe the adult food will allow them to grow slow and steady which supposedly leads to less structural problems as an adult. I remember posting on this before, I'll see if I can find it...
Oh yeah...the question was regarding something else, but here's what I posted regarding adult food:
Our breeder started out feeding her pups puppy food when they were weaned and their legs weren't growing quite right (one longer than the other, etc.). She received a recommendation from another breeder to switch to an adult formula and it would straighten everything out. Sure enough, she noticed an almost immediate change in their growth.
Just my 2 cents, but I don't think puppy food is needed, so I'd say transition now if you want...