We have a 22-week American Mastiff, who'll grow between 3 and 7 pounds per week. (How do I know how much he'll grow? Because it's MY job to pick the puppy up and stand on the scale, which is becoming increasingly difficult!)
We feed:
Half dry food;
Half cooked chicken/ gizzards/ eggs/ peanutbutter.
Augmented with a vitamin our vet gave us, to ensure that our boy has all the right nutrients, as his rate of growth is so rapid right now.
For the chicken, we buy cheap dark meat in bulk from Wal-Mart or Cost Co, chop up the pieces raw, mix 'em in a big bowl, add some soy & teyaki sauce, stir, and put an identical amount into different plastic baggies. We then freeze all the bags, and microwave as necessary, mixing in the cooked food with the raw food, along with an occasional egg or peanutbutter.