Judging by the displays of speed Fluffy and Fido exhibit when they hear the electric can opener, neither has any complaints about what you’re feeding them.

It all looks pretty good—or would to a cat or a dog, you assume. (You’ll stick with people food, thanks.) Chicken, beef, and fish. Chunks of meat in gravy. Crunchy kibble. These are, after all, the same animals that relish raids on the garbage can or litter box. They can’t possibly be that picky.

Pet owners want to know what’s in the food they feed their animals, and they want it to be healthy.

Besides, they’re fat (but not too fat) and happy, and they seem healthy. All must be well in the animal kingdom.

But still, you wonder… so you take a peek at the label on the bag of dog kibble.

Chicken by-product meal. Sounds logical. Corn meal. Hmm. Who knew dogs ate corn? Dried beef pulp. Huh?

Now you’re a relatively educated consumer. You read—and understand, for the most part—the labels on foods you buy for yourself. But you suddenly realize that you haven’t the faintest idea whether the food you buy is good or bad for your pets.

And this bothers you, for good reason.

Customer service representatives at The Iams Company field about 1,000 calls per week about their pet foods, according to Dan Carey, DVM, a veterinarian in the company’s research and development department.

Pets have gained a more important place in our lives over the past few decades. At the same time, we’ve all become more informed consumers, used to interpreting and comparing labels, deciphering manufacturers’ claims, and watching nutritional requirements. It’s no surprise that these two trends have converged—pet owners now want to know what’s in the food they feed their animals, and they want it to be healthy.

Add into the mix a burgeoning number of groups who think no commercial pet food is healthy—they instead advocate feeding home-cooked foods or raw meat and bones—and the picture gets even cloudier.

Rules and regulations

Are pet foods healthy? Are they safe? Good questions—and the variations in quality of ingredients and thoroughness of product research are too wide to make a generalization possible.

"There’s a lot of difference" between all the varieties of generic, popular, and premium foods, said Craig Thatcher, DVM, Ph.D., head of the department of large animal clinical sciences at Virginia-Maryland Regional College of Veterinary Medicine and secretary/treasurer of the American College of Veterinary Nutrition. "There are some I would recommend, and some I wouldn’t recommend," he explained.

There’s no government agency specifically charged with monitoring the pet food industry, but it does fall under the general jurisdiction of the Food and Drug Administration, said Dr. Carey. The FDA decides which vitamin and mineral supplements are "generally regarded as safe" and can be incorporated into pet food. The Federal Trade Commission also regulates claims made by manufacturers.

More direct control is levied by the industry itself, by virtue of the Association of American Feed Control Officials. This group establishes guidelines and definitions for all animal feeds, from livestock to pets, and includes members of the industry, research community, government, and academia.

The AAFCO sets recommended levels of protein, carbohydrates, and so on, although enforcing the adherence to AAFCO guidelines is left to individual state governments. (Meaning that it can vary widely as well.)

Pet food labels are strictly regulated, though—as legal documents, these must adhere exactly to established definitions of ingredients (established by AAFCO), and are prohibited from making certain claims. Ingredients must be listed on the label in descending order by weight, and the label must also contain a minimum/maximum analysis, that will show the upper and lower limits of various ingredients.

Within the boundaries of every regulation, there can be immense variation.

Where’s the beef?

The appearance of most pet foods is so far removed from what would appear on a human’s plate that it’s difficult to discern quality. After all, you may know how to pick out a quality chicken breast at the grocery store—but how do you ascertain the quality of chicken in your cat’s canned food?

In most cases, you can’t—not directly. By looking at the ingredient list, you can determine what AAFCO-defined categories the meat in the product falls into (see sidebar). For instance, a chicken-flavored cat food could contain "chicken," "chicken by-product meal," "chicken liver meal," or "chicken meal."

You may know how to pick out a quality chicken breast at the grocery store—but how do you ascertain the quality of chicken in your cat’s canned food?

All those products vary in terms of their nutritional quality, and there can even be wide variation within the products themselves.

Meat products for pet foods can come from two sources: slaughterhouses and renderers.

Animals destined for slaughter are meant for human consumption, are held to certain regulations, and are inspected at the slaughter facilities. Not all parts of slaughtered animals will be suitable for human consumption—the leftovers can be utilized in pet food, livestock feed, and other products.

Renderers are "recyclers" of many kinds of dead animals—livestock from farms, animals euthanized by veterinarians or animal shelters—and of the leftovers from slaughtered animals. Entire carcasses of different kinds of animals, one certain kind of animal, or just certain parts of certain animals will be ground up to form a rendered product. "Meat and bone meal," "chicken meal," and "chicken liver meal" are examples.

Any pet food ingredients that are a "meal" of some kind are generally rendered products.

"I tell people to avoid by-product meal, and meat and bone meal," said Jean Hofve, DVM, companion animal program coordinator for the Animal Protection Institute, a non-profit advocacy group.

Chicken by-product meal, for example, has the following AAFCO definition: "Consists of the ground, rendered, clean parts of the carcass of slaughtered chicken, such as necks, feet, undeveloped eggs and intestines, exclusive of feathers, except in such amounts as might occur unavoidable in good processing practice."

Such a product may be perfectly nutritious, but quality can also vary widely from batch to batch. A less scrupulous pet food manufacturer can get inferior quality by-product meal cheaply, but from the label, a consumer won’t know the difference.

Is any of this harmful?

Eating a food made from chicken livers might be a queasy concept for you, but your cat or dog (unburdened by cultural and social stigmas or visual images) would likely be thrilled by the idea.

"Certain things used in pet foods aren’t used for human nutrition," said Dr. Thatcher. "The things we don’t eat can be put in pet food and provide a good source of nutrients for pets."

In the wild, for instance, any portion of a carcass would be fair game. "If you were a tiger or a wolf, you’d eat the whole thing, right down to the toenails," Dr. Hofve said.

But some veterinarians and animal enthusiasts worry about the quality of meat products that aren’t "fit for human consumption."

Wendell Belfield, DVM, spent seven years as a veterinary meat inspector for the U.S. Department of Agriculture and the State of California. In 1981, he and Martin Zucker wrote How to Have a Healthier Dog, and voiced concerns about certain chemical residues in slaughterhouse products that weren’t intended for human food, and whether those might be harmful for pets.

"I opened up a Pandora’s box when I wrote about it in 1981," Dr. Belfield said with a chuckle. "It’s hard being the only one saying this. Now they’re saying ‘He was ahead of his time.’ "

Dr. Belfield, who now owns Orthomolecular Specialties, a manufacturer of vitamin and mineral supplements in San Jose, Calif., thinks that many kinds of skin problems and some kinds of epilepsy may be attributed to chemicals in pet foods.

Some veterinarians also think that inflammatory bowel disease could possibly be a kind of food allergy, according to Dr. Hofve.

"There’s nothing that’s really documented. There’s a lot of suspicion," she said.

In 1998, the Animal Protection Institute conducted a survey of 700 veterinarian and veterinary student members of the Association of Veterinarians for Animal Rights. The 150 respondents felt that obesity, inflammatory bowel disease, and developmental bone disease in dogs, and obesity, inflammatory bowel disease, and lower urinary tract disease in cats were the health problems most influenced by nutrition.

More than 90 percent said that they had concerns about commercial pet food, including poor quality of meats, fats, and grains; preservatives; additives; by-product source; and contaminants. Twenty percent frequently recommend home-cooked foods for healthy dogs and cats, while about a third recommended them for animals with specific health issues.

What’s a pet owner to do?

The more educated consumers become about the pet food industry, the more confused they probably get.

"It’s a very complex industry, and it’s very hard to draw generalizations about it," said Dr. Hofve. "Some [pet food companies] are better than others, but the question is: Who are they, and how much better are they?"

Experts can, however, offer some guidance.

"Basically, I tell people that you’ve got to be a smart consumer, and read the label," Dr. Hofve said. "The only place you can get the truth [on the label] is the ingredient statement."

Look for a meat with a name, she added—like beef, lamb, chicken, or turkey. Avoid pet foods that have by-product meal or meat and bone meal as one of the first ingredients listed. Preferably, your pet food of choice won’t use them at all. "These are inferior products," she explained.

You’ll also want to steer clear of foods that don’t list any meat products near the top of the ingredient lists. That means they’re relying more on filler, like vegetable products, and are less nutritious.

She also recommends gradually switching foods at least every three to four months, even if it’s just within a particular brand name. You’ll avoid developing a finicky pet, and will be more assured that you’re providing a balanced diet and minimizing the effects of any possible harmful ingredients.

Companies with nationwide distribution will likely offer higher quality products, Dr. Hofve said. Enforcement of pet food regulations varies from state to state—if a state is lax about enforcement, a local pet food supplier can get away with more. National distributors will have to produce products that can comply with the strictest regulations in the country, no matter where they actually end up being sold.

The better pet food companies will also go above and beyond current regulations. For instance, a company like Iams might spend 10 years bringing a pet food product idea from inception to the store shelf, including detailed research and feeding studies, Dr. Carey said.

"We want to be able to explain to people why a food is better for their dog. And we want to explain to regulators the basis for making those statements," he explained.

Pet foods can get an AAFCO stamp of approval in three ways, Dr. Thatcher said. The first is by providing a chemical analysis of a food, looking at the nutrient profile, and comparing it to the AAFCO standard. The same information can also be determined mathematically, calculating what the nutrient profile would be.

With either method, actual feeding of the product to pets is not required. "Not all pet foods have been fed to dogs and cats," Dr. Thatcher said.

The third method is via AAFCO-standardized feeding trials—giving a specific food to eight dogs for 26 weeks, and assessing the dogs’ health and how well those nutrients are utilized. A food that has provided this information will indicate it on the label, and such tests are often considered better indicators of how well the nutrients in a pet food will be absorbed and utilized.

Better manufacturers will conduct even more thorough research, with more animals, for longer periods of time. "We collect the stool and urine [and analyze it]. We know what goes in and what comes out—whatever doesn’t come out stayed in the dog," Dr. Carey said. Some products may have "thousands and thousands of dog days" involved in their development, he said.

Consumers have to expect to go above and beyond the norm as well, Dr. Thatcher explained. While the pet food label is a good place to start for basic information, you’ll need more than that to make an informed decision on what food to buy.

Pet foods are required to list a guaranteed analysis for the minimum and maximum amount of crude protein, crude fiber, crude fat, and moisture content. These numbers won’t be exact—if a label says a food contains a minimum of 15 percent protein, there could in fact be 17 or 18 percent protein in it, which might not be safe for all pets.

"The best thing to go by is the nutrient profile," said Dr. Thatcher. This is available from the manufacturer, and you can request it by calling the toll-free number provided on a bag of pet food. This profile won’t give minimums or maximums for the percentages of various ingredients, but instead an average—a much more accurate and useful number.

"That information is much better information than what’s on the label," Dr. Thatcher said.

The company can also often offer a better explanation for what’s listed on the ingredient label, and answer your questions, said Dr. Carey. One company’s chicken by-products may be very different from another company’s—a reputable manufacturer will be able to give you a better explanation of what those by-products are.

"If every consumer called… it would put the manufacturers on notice that a lot of people are paying attention," said Dr. Hofve.

"Certain things used in pet foods aren’t used for human nutrition," said Dr. Thatcher. "The things we don’t eat can be put in pet food and provide a good source of nutrients for pets."

"I tried to give this to the profession," Dr. Belfield said of the concerns voiced in his book. "They ignored me at first. I gave the book to pet owners, it gave them ammunition, and they went to the pet food companies."

"The industry is not as dishonest and sleazy as everyone would think," Dr. Hofve added.

"In a perfect world, they would all be non-profit. It’s the money that drives it," she said. "The people who try to make the food good are constantly at odds with the budget guys."

It’s the educated pet owners who know that the value of a food isn’t in the price.