Dog eating dog food

A pet-food manufacturer recalled 60 million units over the weekend after at least nine cats and a dog died of kidney failure. No one has identified the source of the contamination, but the company said the recalled products included a suspect batch of wheat gluten. What else goes into pet food?

Meat that we don't want for ourselves, for the most part. Packaged pet food often contains ingredients like "meat byproducts" or "chicken meal," which come from animal parts that Americans rarely consume—heads, bones, blood, and organs. It might also contain parts from sick or dying animals.

Rendering plants grind the meat byproducts and ship the meal to pet-food makers. Next, the manufacturers combine the meal with carbohydrates such as corn, thickeners like guar gum, vitamins, minerals, food coloring, and preservatives. To make wet food, this glop is then heated in a pressure cooker and canned or sealed in a pouch. For dry pellets, the stuff is heated, cut into tiny pieces, dried, and then wrapped for shipment. More expensive brands tend to have fixed formulas, while cheaper brands change recipes to include ingredients that happen to be selling cheap. (They might decide to replace corn with wheat, for example, if wheat prices were especially low.)

Thanks to the U.S. Food and Drug Administration—which oversees the pet-food industry with the advice of the Association of American Feed Control Officials—the list of ingredients on a tin of dog chow gives you a general sense of what's inside. But pet-food companies manipulate the order of the list such that meat (and meat by products) appear first, even when other ingredients are used in larger quantities. For instance, a can of cat food may list wheat flour and ground wheat as two ingredients; that way it seems like there's more meat than grain in the recipe.

The product name, however, can be telling. According to AAFCO rules, you can't call a product "Tuna for Cats" unless it's at least 95-percent tuna (not counting water for processing). A name like "Beef Entrée" or "Turkey and Giblets Dinner" means that the main ingredients make up 25 to 95 percent of the meal.

Most veterinarians don't think there's a fundamental flaw with the pet-food industry. (This week's recall likely resulted from more specific problems.) Consumers may not like to think of Fido eating intestines or brains, but animal nutritionists say the byproducts are safe and that commercial pet food provides a complete diet for dogs and cats. If anything, pet food may be a little too wholesome. Pets, like their owners, are putting on the pounds: A 2003 report found that a quarter of domestic pets are overweight. Dogs are getting so fat that the FDA approved a weight-loss drug for canines this year.

Explainer thanks Tony Buffington of Ohio State University's College of Veterinary Medicine and Ron Faoro off the California Veterinary Medical Association.