Here is what Pamela sent me... I hope this helps
Hi Andrea - I'm at work, so I don't have anything with me; however, if you do a Google search for Pat Hastings, I believe you'll get some hits that will provide you with more concrete evdience. She's viewed as an expert in structure and puppy evaluations as well as nutrition, so I'm sure you can find something useful.
I did a quick search and found a few links that you may find helpful:
http://www.heartlandgdr.org/why_we_d...puppy_food.htm
http://answers.yahoo.com/question/in...6101253AAHxtLZ
http://en.allexperts.com/q/German-Sh...puppy-food.htm
Some of the links also include differing points of view, so each person can make informed/educated decisions, but I can tell you first hand, that since I quit feeding puppy food, my dogs have all developed better fronts (legs, chests, feet) skeletally, so I will continue what works for me.
Hope this helps...