I asked this very question of Purina in a e-mail. Below is their reply.
"Thank you for contacting Nestlé Purina PetCare Company.
Congratulations on your soon-to-be new puppy! Based on the information you provided in your email, we would recommend that you feed your puppy our Purina(r) Pro Plan(r) brand Dog Food - Performance Formula - All Life Stages. Because this product is complete and balanced for maintenance for all life stages of dogs, you may feed it to your dog from the time it is a puppy throughout its entire life through adulthood.
Our Purina(r) Pro Plan(r) brand Dog Food - Performance Formula - All Life Stages is specially formulated for the nutritional needs of hardworking and highly active dogs. It is designed with a 30% protein: 20% fat ratio which supports increased endurance and lean muscle mass. This product also provides concentrated nutrition, which optimizes oxygen metabolism (VO2 MAX) so dogs burn fat more efficiently. Real chicken is the #1 ingredient. For additional information about our Purina(r) Pro Plan(r) brand Dog Food - Performance Formula - All Life Stages, we would recommend visiting our website,
www.proplan.com.
We would recommend you utilize the feeding guidelines found on the product packaging to determine a starting point for feeding. We recommend monitoring your puppy's body condition, and adjusting the amount fed each day to ensure your puppy maintains a lean body conformation. When your puppy is not hunting or in preparation for hunting or trials, the amount fed may be less than during these times. For more information on the ideal body condition, please click on the link below.
http://www.purina.com/dog/weight-and-exercise/bodycondition.aspx
We hope you find this information helpful.
Again, thank you for visiting our website."