Liz,
I have heard about large breed food. I think it is designed to keep them from growing too much, too soon. Unfortunately, I didn't know about it when Honey and Lilly were puppies! They 'grew up" on Purina Puppy Chow, and then I switched them later.
But I think going the "large breed" route is probably a good thing, or switching to adult food earlier than suggested on the label.
I'd ask the vet, to be sure, but in my case, my vet had very few suggestions regarding feeding. Recently, though, he said, "whatever you're doing, keep on doing it". My girls look wonderful and are having no allergy problems for the first time in their lives.
Logan