Did you know that basic veterinarian training in nutrition is limited to 3 hours, unless your vet specifically ]seeks additional training?
As with people, the quality, amount, and frequency of what you feed your animal can affect their health and longevity. Generally, the more processed a pet food is, the less nutritional value it will have for your animal. Dry food has been processed in more than one way from the original meat that it came from; and although many brands are tasty to your animals, beware of feeding only dry food, and leaving it out for long periods of time. In cats, leaving dry food left out over time, as they cointinuously breathe in its odor can affect the Ph of the animal, causing it to become more alkaline, and so there is more susceptibility to urinary tract infection.
Pets who eat at least some raw food, will tend to have less dental problems and need less dental cleanings, as this food is the closest to what our dogs and cats would eat in the wild, if they were not domesticated.
Canned food is an alternative, but should have some living food, such as canned or fresh vegetables, added on a regular basis. Select a brand that does not have additives, preservatives, or by-products added. Althoughthese brands are more expensive, your animal's health will be better in the long run.
Good sources on pet diet and holistic care include Dr. Richard Pitcairn's Guide to Holistic Health for Dogs and Cats, The New Natural Cat, by Anitra Frasier, and Diane Stein's The Natural Remedy Book for Dogs and Cats.