Purina is one of the worst brands I can think of. California Naturals is a good food, but I recomend Artemis Maximal Dog. If that is a little out of your price range, then Acana Grasslands is the next best one. Whatever you feed, I highly recomend adding L. Acidophilus to your dog's food. This well known probiotic helps balance intestinal microflora when it has been disturbed by illness or antibiotic use. Acidophilus helps normalize digestion, which helps to reduce gas, bloating, and bad breath. I also recomend adding Saccharomyces Boulardii. Clinical research with this probiotic has demonstrated its consistent ability to resolve diarrhea, whether related to acute infection or to chronic inflammatory bowel dysfunction. Slippery Elm Bark is another highly recomended supplement. This herb has been traditionally used to soothe the digestive tract and intestinal walls. Slippery elm provides mucilage, which forms a slippery substance when combined with water. Mucilage can reduce irritation of intestinal tissues, promote healthy detoxification in the bowel, and help maintain regular elimination patterns. I also recomend N-Acetyl-Glucosamine. N-A-G is a form of glucosamine that is found naturally in the mucous membranes of the gastrointestinal tract. It also helps to support the body’s natural protective barriers against acids, over-activity of enzymes, and invading microorganisms by supporting healthy functioning of the mucosal lining throughout the intestines.