I feed my dogs a raw food diet. Before I switched, I fed them Canidae.
Read the ingredients of your dog food. The first 5 products should be more meats then grain. Brewer's rice, corn and meat by products shouldn't be listed in the top 5 either.
Large breed is a marketing ploy. Fancy name=more money.
Try adding some plain yogurt and a raw egg, shell and all to the dry dog food.