dog food brands

Question
i have a 16 week old female German shepherd and i feed her Purina puppy chow for large breed dogs, ( she is also no spayed yet) is this food ok? i am always reading things on different websites rating the first 5 ingredients in different dog foods pedigree, iams, science diet etc.and i would love to hear your opinion/recommendation
thanks : )

Answer
I think much of what you read is influenced by those selling more expensive foods.  The ratings are based on subjective evaluations of the ingredients, playing on the emotions of people at best.  The worst has distortions, half truths. and some outright lies.  Have you read the Purina is mostly corn and dogs can't digest corn?  If so, how has she managed to live so far?  

The one thing that is true is that dogs don't digest corn as well as some other things and Purina and similar foods do produce larger, softer stools that are harder to clean up.  The only other thing wrong with the Purina Puppy Chow is common to nearly all puppy chows, so rich it produces faster growth than is good for large breed puppies' joints.  Switching to an adult chow for the larger breeds at 4 months, slows growth and helps develop sturdier joints.

Your dog definitely should be narrower at the waist than the hips and chest. You
should be able to easily feel the ribs, but not see them. Each dog is different.
Standard recommendations are a good place to start, but each dog must have its
food and exercise adjusted to its individual needs. Here is a link to a good
illustrated guide, http://www.longliveyourdog.com/twoplus/RateYourDog.aspx

Shepherds are more likely to be on the thin side, even the ribs showimg more than the ideal shown above.  If so, it is Ok.  

What I would do is switch to an adult chow now.  If you want to get smaller, firmer stools any of the brands you mentioned or one of the other Purina brands would be fine.  I think most dogs will thrive on most foods, but there isn't any diet that is right for all.  I have seen thousands of dogs thriving on common brands in the service dog programs.  Iams is the most popular.  Maybe the ingredients in them are the junk many say, but dogs do great on them.  While I suspect the premium brands are a waste of money, I don't know that there is any problem with them.  

For all viewpoints about dog food see http://www.woodhavenlabs.com/articles2.html#nutrition  I consider some of the links kooks.