This is a question that we often get from sitters and owners who work with Rover. Help the community out by answering them in our forum!
After a lot of research into this exact question, I chose Fromm's Gold Large Breed Puppy. Stay away from grain free foods for the time being. Puppy's need a balanced diet, and grains are essential for domesticated animals like dogs. For large breeds like shepherd's, I suggest moving to their adult version of the food around 8 months but your vet can advise based on his growth rate when the time is right.
What do you have against other dogs? They should get food too!