What's Really in Pet Food

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This report explores the differences between what consumers think they are buying and what they are actually getting. It focuses in very general terms on the most visible name brands -- the pet food labels that are mass-distributed to supermarkets and discount stores -- but there are many highly respected brands that may be guilty of the same offenses.



There are hundreds of different pet foods available in this country. And while many of the foods on the market are similar, not all of the pet food manufacturing companies use poor quality or potentially dangerous ingredients.


Although the purchase price of pet food does not always determine whether a pet food is good or bad, the price is often a good indicator of quality. It would be impossible for a company that sells a generic brand of dog food at $9.95 for a 40-lb. bag to use quality protein and grain in its food. The cost of purchasing quality ingredients would be much higher than the selling price.

The protein used in pet food comes from a variety of sources. When cattle, swine, chickens, lambs, or other animals are slaughtered, the choice cuts such as lean muscle tissue are trimmed away from the carcass for human consumption. However, about 50% of every food-producing animal does not get used in human foods. Whatever remains of the carcass -- bones, blood, intestines, lungs, ligaments, and almost all the other parts not generally consumed by humans -- is used in pet food, animal feed, and other products. These "other parts" are known as "by-products," "meat-and-bone-meal," or similar names on pet food labels.

The Pet Food Institute -- the trade association of pet food manufacturers -- acknowledges the use of by-products in pet foods as additional income for processors and farmers: "The growth of the pet food industry not only provided pet owners with better foods for their pets, but also created profitable additional markets for American farm products and for the byproducts of the meat packing, poultry, and other food industries which prepare food for human consumption."1

Many of these remnants provide a questionable source of nourishment for our animals. The nutritional quality of meat and poultry by-products, meals, and digests can vary from batch to batch. James Morris and Quinton Rogers, two professors with the Department of Molecular Biosciences, University of California at Davis Veterinary School of Medicine, assert that, "There is virtually no information on the bioavailability of nutrients for companion animals in many of the common dietary ingredients used in pet foods. These ingredients are generally by-products of the meat, poultry and fishing industries, with the potential for a wide variation in nutrient composition. Claims of nutritional adequacy of pet foods based on the current Association of American Feed Control Officials (AAFCO) nutrient allowances ('profiles') do not give assurances of nutritional adequacy and will not until ingredients are analyzed and bioavailability values are incorporated."2

Meat and poultry meals, by-product meals, and meat-and-bone meal are common ingredients in pet foods. The term "meal" means that these materials are not used fresh, but have been rendered. What is rendering? Rendering, as defined by Webster's Dictionary, is "to process as for industrial use: to render livestock carcasses and to extract oil from fat, blubber, etc., by melting." Home-made chicken soup, with its thick layer of fat that forms over the top when the soup is cooled, is a sort of mini-rendering process. Rendering separates fat-soluble from water-soluble and solid materials, removes most of the water, and kills bacterial contaminants, but may alter or destroy some of the natural enzymes and proteins found in the raw ingredients. Meat and poultry by-products, while not rendered, vary widely in composition and quality.


Animal and Poultry Fat










Additives and Preservatives






Additives in Processed Pet Foods

Anticaking agents
Antimicrobial agents
Coloring agents
Curing agents
Drying agents
Firming agents
Flavor enhancers
Flavoring agents
Flour treating agents
Formulation aids
Leavening agents
Nonnutritive sweeteners
Nutritive sweeteners
Oxidizing and reducing agents
pH control agents
Processing aids
Solvents, vehicles
Stabilizers, thickeners
Surface active agents
Surface finishing agents


The Manufacturing Process

How Pet Food Is Made


Most dry food is made with a machine called an expander or extruder. First, raw materials are blended, sometimes by hand, other times by computer, in accordance with a recipe developed by animal nutritionists. This mixture is fed into an expander and steam or hot water is added. The mixture is subjected to steam, pressure, and high heat as it is extruded through dies that determine the shape of the final product and puffed like popcorn. The food is allowed to dry, and then is usually sprayed with fat, digests, or other compounds to make it more palatable. Although the cooking process may kill bacteria in pet food, the final product can lose its sterility during the subsequent drying, fat coating, and packaging process. A few foods are baked at high temperatures rather than extruded. This produces a dense, crunchy kibble that is palatable without the addition of sprayed on palatability enhancers. Animals can be fed about 25% less of a baked food, by volume (but not by weight), than an extruded food.

Ingredients are similar for wet, dry, and semi-moist foods, although the ratios of protein, fat, and fiber may change. A typical can of ordinary cat food reportedly contains about 45-50% meat or poultry by-products. The main difference between the types of food is the water content. It is impossible to directly compare labels from different kinds of food without a mathematical conversion to "dry matter basis."5 Wet or canned food begins with ground ingredients mixed with additives. If chunks are required, a special extruder forms them. Then the mixture is cooked and canned. The sealed cans are then put into containers resembling pressure cookers and commercial sterilization takes place. Some manufacturers cook the food right in the can.

There are special labeling requirements for pet food, all of which are contained in the annually revised Official Publication of AAFCO.6 The use of the terms "all" or "100%" cannot be used "if the product contains more than one ingredient, not including water sufficient for processing, decharacterizing agents, or trace amounts of preservatives and condiments." Products containing multiple ingredients are covered by AAFCO Regulation PF3(b) and (c). The "95% rule" applies when the ingredient(s) derived from animals, poultry, or fish constitutes at least 95% or more of the total weight of the product (or 70% excluding water for processing).

Because all-meat diets are usually not nutritionally balanced, they fell out of favor for many years. However, due to rising consumer interest in high quality meat products, several companies are now promoting 95% and 100% canned meats as a supplemental feeding option.

The "dinner" product is defined by the 25% Rule, which applies when "an ingredient or a combination of ingredients constitutes at least 25% of the weight of the product" (excluding water sufficient for processing) as long as the ingredient(s) shall constitute at least 10% of the total product weight; and a descriptor that implies other ingredients are included in the product formula is used on the label. Such descriptors include "recipe," "platter," "entree," and "formula." A combination of ingredients included in the product name is permissible when each ingredient comprises at least 3% of the product weight, excluding water for processing, and the ingredient names appear in descending order by weight.

The "with" rule allows an ingredient name to appear on the label, such as "with real chicken," as long as each such ingredient constitutes at least 3% of the food by weight, excluding water for processing.

The "flavor" rule allows a food to be designated as a certain flavor as long as the ingredient(s) are sufficient to "impart a distinctive characteristic" to the food. Thus, a "beef flavor" food may contain a small quantity of digest or other extract of tissues from cattle, without containing any actual beef meat at all.

What Happened to the Nutrients?







The National Research Council (NRC) of the Academy of Sciences set the nutritional standards for pet food that were used by the pet food industry until the late 1980s. The NRC standards, which still exist and are being revised as of 2001, were based on purified diets, and required feeding trials for pet foods claimed to be "complete" and "balanced." The pet food industry found the feeding trials too restrictive and expensive, so AAFCO designed an alternate procedure for claiming the nutritional adequacy of pet food, by testing the food for compliance with "Nutrient Profiles." AAFCO also created "expert committees" for canine and feline nutrition, which developed separate canine and feline standards. While feeding trials can still be done, a standard chemical analysis may be also be used to determine if a food meets the profiles.

Chemical analysis, however, does not address the palatability, digestibility, or biological availability of nutrients in pet food. Thus it is unreliable for determining whether a food will provide an animal with sufficient nutrients.

To compensate for the limitations of chemical analysis, AAFCO added a "safety factor," which was to exceed the minimum amount of nutrients required to meet the complete and balanced requirements.

The digestibility and availability of nutrients is not listed on pet food labels.

The 100% Myth -- Problems Caused by Inadequate Nutrition



Dry commercial pet food is often contaminated with bacteria, which may or may not cause problems. Improper food storage and some feeding practices may result in the multiplication of this bacteria. For example, adding water or milk to moisten pet food and then leaving it at room temperature causes bacteria to multiply.8 Yet this practice is suggested on the back of packages of some kitten and puppy foods.








What Consumers Can Do

For Further Reading about Animal Nutrition


The books listed above are a fraction of all the titles currently available, and the omission of a title does not necessarily mean it is not useful for further reading about animal nutrition.

Please note: The Animal Protection Institute is not a bookseller, and cannot sell or send these books to you. Please contact your local book retailer or an online bookstore, who can supply these books based on the ISBN provided for each title.

What API is Doing

Who to Write

AAFCO Pet Food Committee
Dr. Rodney Noel -- Chair
Office of Indiana State Chemist
Purdue University
1154 Biochemistry Building
West Lafayette, IN 47907-1154

FDA -- Center for Veterinary Medicine
Sharon Benz
7500 Standish Place
Rockville, MD 20855

Pet Food Institute
2025 M Street, NW, Suite 800
Washington, DC 20036
Fax 202-367-2120


Association of American Feed Control Officials Incorporated. Official Publication 2001. Atlanta: AAFCO, 2001.

Barfield, Carol. FDA Petition, Docket Number 93P0081/CP1, accepted February 25, 1993.

Becker, Ross. "Is your dog's food safe?" Good Dog!, November/December 1995, 7.

Cargill, James, MA, MBA, MS, and Susan Thorpe-Vargas, MS. "Feed that dog! Part VI." DOGworld, December 1993, 36.

Case, Linda P., M.S., Daniel P. Carey, D.V.M., and Diane A. Hirakawa, Ph.D. Canine and Feline Nutrition: A Resource for Companion Animal Professionals. St. Louis: Mosby, 1995.

Coffman, Howard D. The Dry Dog Food Reference. Nashua: PigDog Press, 1995.

Corbin, Jim. "Pet Foods and Feeding." Feedstuffs, July 17, 1996, 80-85.

Knight-Ridder News Syndicate. "Nature's Recipe Recalls Dog Food That Contains Vomitoxin." August 28, 1995.

Morris, James G., and Quinton R. Rogers. "Assessment of the Nutritional Adequacy of Pet Foods Through the Life Cycle." Journal of Nutrition, 124 (1994): 2520S-2533S.

Newman, Lisa. What's in your pet's food? Tucson & Phoenix: Holistic Animal Care, 1994.

New York State Department of Agriculture and Markets. 1994 Commercial Feed Analysis Annual Report. Albany: Division of Food Inspection Services, 1995.

Parker, J. Michael. "Tainted dog food blamed on corn." San Antonio Express News, April 1, 1999.

"Petfood activist." Petfood Industry, September/October 1991, 4.

Pet Food Institute. Fact Sheet 1994. Washington: Pet Food Institute, 1994.

Phillips, Tim, DVM. "Rendered Products Guide." Petfood Industry, January/February 1994, 12-17, 21.

Pitcairn, Richard H., D.V.M., Ph.D., and Susan Hubble Pitcairn. Dr. Pitcairn's Complete Guide to Natural Health for Dogs & Cats. Emmaus: Rodale, 1995.

Plechner, Alfred J., DVM, and Martin Zucker. Pet Allergies: Remedies for an Epidemic. Inglewood: Wilshire Book Co., 1986.

Rhode Island Department of Environmental Management, Division of Agriculture. 1994 Report of the Inspection and Analysis of Commercial Feeds, Fertilizers and Liming Materials. Providence: Division of Agriculture, 1995.

Roudebush, Philip, DVM. "Pet food additives." JAVMA, 203 (1993): 1667-1670.

Rouse, Raymond H. "Feed Fats." Petfood Industry, March/April 1987, 7.

Sellers, Richard. "Regulating petfood with an open mind." Petfood Industry, November/December 1990, 41-44.

Smith, Carin A. "Research Roundup: Changes and challenges in feline nutrition." JAVMA 203 (1993), 1395-1400.

Strombeck, Donald. R. Home-Prepared Dog and Cat Foods: The Healthful Alternative. Ames: Iowa State University Press, 1999.

Winters, Ruth, M.S. A Consumer's Dictionary of Food Additives. New York: Crown, 1994.

Wysong, R. L. "The 'complete' myth." Petfood Industry, September/October 1990, 24-28.

[Wysong, R. L.] Fresh and Whole: Getting Involved in Your Pet's Diet. Midland: Wysong Corporation, 1990.

Wysong, R. L. Rationale for Animal Nutrition. Midland: Inquiry Press, 1993.


1. Pet Food Institute, 2.
2. Morris, 2520S.
3. Corbin, 81.
4. Cargill, 36.
5. The conversion is: ingredient percentage divided by (100 minus moisture percentage).
6. Official Publication, Regulation PE3, 114-115.
7. Wysong, Rationale, 40-41.
8. Strombeck, 50-52.
9. Smith, 1397.

(Revised 01/29/02)

Copyright © 1997-2002 Animal Protection Institute.

Because this e-report is frequently revised, it is no longer available in printed form. However, you can download a PDF of the current version from the Born Free/API website.

The original of this page can be found at The Born Free/Animal Protection Institue's website