You’re right the first ingredient is corn but it does have other stuff, including taurine.
Here’s the list from Purina Cat Chow. Doesn’t look that great, but it does keep them alive. I know people who have 15-18 year old cats who have eaten nothing but this stuff.
Ingredients:
Corn meal, poultry by-product meal, corn gluten meal, soy flour, animal fat preserved with mixed-tocopherols (form of Vitamin E), powdered cellulose, animal liver flavor, soybean hulls, malt extract, calcium carbonate, phosphoric acid, salt, choline chloride, potassium chloride, taurine, zinc sulfate, Vitamin E supplement, ferrous sulfate, manganese sulfate, parsley flakes, niacin, added color (Red 40, Yellow 5, Blue 2), copper sulfate, Vitamin A supplement, calcium pantothenate, thiamine mononitrate, riboflavin supplement, Vitamin B-12 supplement, pyridoxine hydrochloride, folic acid, Vitamin D-3 supplement, calcium iodate, biotin, menadione sodium bisulfite complex (source of Vitamin K activity), sodium selenite. I-4500
My cat of 10 years will eat nothing but Friskies Surfin’ Turfin’. When she was a kitten she ate canned cat food but one day turned her nose up at it. I gave away a dozen cans of expensive cat food. She’s in very good health, very active and not at all fat.
Until a week ago she showed no interest in people food, not even real meat. I had made a pizza. It was hot from the oven and I use a lot of crushed red pepper. She decided to check it out. She snuck up on the pizza and gave the sauce a taste. Her tongue picked up a couple flakes of pepper, she shook her head and swatted the pizza a couple times. I doubt she’ll try it again.
This is what we feed our three cats; one of them will not eat anything else.