Once, back in the day, Purina made a pretty decent food, better than most that were available. It's not even remotely close to the quality it used to be. Back then, the cheapest ingredients to use were the ones that had the least "scientific" tinkering - from the lowest on the chain of farms that couldn't afford the expensive new chemicals, drugs and other goodies. Those were the products that were considered inferior and went into the pet food industry. The "higher quality" stuff that had all of those great additives that made it tastier and tenderer, ad nauseum commanded a higher price and went to the consumers at the top of the economic food chain. Now things are reversed, and the big, corporately produced foods are the cheapest; also the most adulterated. Not only that, but the stuff that is being used in the large manufacturers pet foods are the leavings - the diseased stuff, the contaminated, anything deemed unfit for human consumption. Charley was a die-hard Purina guy for years - he wouldn't have his dogs touch it now.
But we do the best we can by our critters. Mine eat healthier than I do now . . . but truth be told I care a lot more about something happening to them.