Few people appreciate just how critical proper nutrition is to our feline friends. A significant number of my patients present with medical problems that have their roots in an incorrect diet.
Domestic cats are the direct descendants of Felis libyca, the desert wildcat of North Africa, the Negev, and Arabia. In this environment, the primary food sources for the cat were birds, reptiles, small rodents, and insects. You may note that fish are not on the list - nor should they be. Water is genuinely scarce in the Sahara, as are fish.
So as one might suspect, the healthiest protein source for cats is poultry (analogous to small birds and reptiles), with beef (analogous to mice/rats) a close second. Lamb and other novel proteins are not the best first choice, and fish is completely inappropriate from a biological standpoint.
My first bottom line recommendation for a maintenance diet in cats is that it NOT contain fish. Fish oil itself is a valuable nutrient, but fish flesh or fish meal is problematic. While healthy for us humans to eat, fish is implicated in (and I believe it to be directly causative of) a large percentage of the lower urinary tract disease, skin disease, and gastrointestinal disease I see at Cat's Meow Veterinary Clinic.
The second bottom line recommendation I make for a cat food is that it be tested for nutritional adequacy. Anybody can throw together a cat food that looks perfectly acceptable on paper according to the guaranteed analysis and other numerical data, but that diet could have serious problems with nutrient bioavailability. Because of this, we only recommend maintenance foods that have the following statement of nutritional adequacy on the label (known as the AAFCO Statement):
"Animal feeding tests using AAFCO procedures substantiate that (name of food) provides complete and balanced nutrition for maintenance of adult cats."
The best kitten foods have a similar statement pertaining to growth of kittens and maintenance of pregnant and lactating females.
There may be times in a cat's life when we need to feed it a diet that violates these two guidelines in the interest of special needs during illness. And if a cat has been happily enjoying a food which contains fish without adverse consequences (that is otherwise an excellent food) for years there may not be any need to switch. But in general you can't go wrong by following this basic advice.
Several kibble foods which as of this writing meet these criteria are:
*Science Diet - any flavor/variety kibble not containing fish on ingredient list
*Nutro Natural Choice Complete Care Indoor - any flavor not containing fish
*Max Cat Adult Roasted Chicken
*Purina One Special Care Sensitive Systems
Next time I'll address the dry food vs canned food issue and my recommendations about that.