What’s really in pet food

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When a cat requires a special diet because of a medical condition, then the vet knows best. If the cat is healthy and the owner wants to maintain good health by providing the cat with a good maintenance diet, then Cat Rescue Network recommends that the owner becomes informed about cat nutrition. The following articles are but a few of many available on the web. Pet store owners, pet food companies and veterinarians are other good sources of information.

Most consumers don’t know that the pet food industry is an extension of the human food and agriculture industries. Pet food provides a convenient way for slaughterhouse offal, grains considered “unfit for human consumption,” and similar waste products to be turned into profit. This waste includes intestines, udders, heads, hooves, and possibly diseased and cancerous animal parts.

The Pet Food Institute — the trade association of pet food manufacturers — has acknowledged 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 by-products of the meat packing, poultry, and other food industries which prepare food for human consumption.” 1

Label Basics

There are special labelling requirements for pet food, all of which are contained in the annually revised Official Publication of AAFCO.2 While AAFCO does not regulate pet food, it does provide model regulations and standards that U.S. pet food makers follow.

The name of the food provides the first indication of the food’s content. The use of 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.”

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 not nutritionally balanced and cause severe deficiencies if fed exclusively, they fell out of favour 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 supplemental feeding options.

The “25% Rule defines the “dinner” product.” This applies when “an ingredient or a combination of ingredients constitutes at least 25% of the weight of the product (excluding water sufficient for processing)”, or at least 10% of the dry matter weight, and a descriptor such as “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. 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 ingredient constitutes at least 3% of the food by weight, excluding water for processing.

The “flavour” rule allows a food to be designated as a particular flavour as long as the ingredient(s) is sufficient to “impart a distinctive characteristic” to the food. Thus, a “beef flavour” food may contain a small quantity of digest or other extracts of tissues from cattle, or even an artificial flavour, without actual beef meat.

The ingredient list is the other major key to what’s really in that bag or can. Ingredients must be listed in descending order of weight. The ingredient names are legally defined. For instance, “meat” refers to cows, pigs, goats and sheep and only includes specified muscle tissues. Detailed definitions are published in AAFCO’s Official Publication, revised annually, but can also be found in many places online.

The guaranteed analysis provides a general guide to the food composition. Crude protein, fat, fibre, and total moisture must be listed. Some companies also voluntarily list taurine, Omega fatty acids, magnesium, and other items they deem essential — by marketing standards.

Pet Food Standards and Regulations

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 original NRC standards 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 are sometimes still done, they are expensive and time-consuming. Standard chemical analysis may also be used to make sure that a food meets the profiles. In either case, there will be a statement on the label stating which method was used. However, because of the “family rule” in the AAFCO book, a brand can say that feeding tests were done if it is “similar” to a food that was actually tested on live animals. There is no way to distinguish the lead product from its “family members.” The label will also state whether the product is nutritionally adequate (complete and balanced), and what life stage (adult or growth) the food is for. A food that says “all life stages” meets the growth standards and can be fed to all ages.

Chemical analysis, however, does not address the palatability, digestibility, or biological availability of nutrients in pet food. Thus it is unreliable to determine whether 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.

In 2006, new NRC standards were published; but it will take several years for AAFCO’s profiles to be updated and adopted, let alone accepted by the states.

The pet food industry loves to say that it’s more highly regulated than human food, but that’s not true. Pet food exists in a regulatory vacuum; laws are on the books, but enforcement is another story. The FDA has nominal authority over pet foods shipped across state lines. But the real “enforcers” are the feed control officials in each state. They are the ones who look at the food and, in many instances, run basic tests to make sure the food meets its Guaranteed Analysis, the chart on the label telling how much protein, fat, moisture, and fibre are present. But regulation and enforcement vary tremendously from state to state. Some, like Texas, Minnesota, and Kentucky, run extensive tests and strictly enforce their laws; others, like California, do neither.

Pet Food Ingredients

Animal Protein

Dogs and cats are carnivores and do their best on a meat-based diet. The protein used in pet food comes from a variety of sources. When cattle, swine, chickens, lambs, or other animals are slaughtered, lean muscle tissue is trimmed away from the carcass for human consumption, along with the few organs that people like to eat, such as tongues and tripe.

However, about 50% of every food animal does not get used in human foods. Whatever remains of the carcass — heads, feet, bones, blood, intestines, lungs, spleens, livers, ligaments, fat trimmings, unborn babies, and other parts not generally consumed by humans — is used in pet food, animal feed, fertilizer, industrial lubricants, soap, rubber, and other products. These “other parts” are known as “by-products.” By-products are used in feed for poultry, livestock, and pet food.

The nutritional quality of by-products, meals, and digests can vary from batch to batch. James Morris and Quinton Rogers of the University of California at Davis Veterinary School assert that “[pet food] 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. They will not until ingredients are analyzed and bioavailability values are incorporated.” 3

Meat or poultry “by-products” are very common in wet pet foods. Remember that “meat” refers to only cows, swine, sheep, and goats. Since sheep and goats are rare compared to the 37 million cows and 100 million hogs slaughtered for food yearly, nearly all meat by-products come from cattle and pigs.

The better brands of pet food, such as many “super-premium,” “natural,” and “organic” varieties, do not use by-products. On the label, you’ll see one or more named meats among the first few ingredients, such as “turkey” or “lamb.” These meats are still mainly leftover scraps; in the case of poultry, bones are allowed, so “chicken” consists primarily of backs and frames—the spine and ribs, minus their expensive breast meat. The small amount of meat left on the bones is the meat in the pet food. Meat, poultry, by-product, and meat-and-bone meals are common ingredients in dry pet foods. The term “meal” means that these materials are not used fresh but have been rendered. While there are chicken, turkey, and poultry by-product meals, there is no equivalent term for mammal “meat by-product meal” — it is called “meat-and-bone-meal.” It may also be referred to by species, such as “beef-and-bone-meal” or “pork-and-bone-meal.”

Vegetable protein

The amount of grain and vegetable products used in pet food has risen dramatically. Plant products now replace a considerable proportion of the meat that was used in the earliest commercial pet foods. This had led to severe nutritional deficiencies that have been corrected along the way, although many animals died before science caught up.

Most dry foods contain a large amount of cereal grain or starchy vegetables to provide texture. These high-carbohydrate plant products also offer a cheap source of “energy” — the rest of us call it “calories.” Gluten meals are high-protein extracts from which most carbohydrate has been removed. They are often used to boost protein percentages without expensive animal-source ingredients. Corn gluten meal is the most commonly used for this purpose. Wheat gluten is also used to create shapes like cuts, bites, chunks, shreds, flakes, and slices and as a thickener for gravy. Most foods containing vegetable proteins are among the poorer quality foods.

A recent fad, “low-carb” pet food, has some companies steering away from grains and using potatoes, green peas, and other starchy vegetables as substitutes. Except for animals allergic to grains, dry low-carb diets offer no particular advantage to pets. They also tend to be very high in fat and, if fed free-choice, will result in weight gain. Canned versions are suitable for the prevention and treatment of feline diabetes, as part of a weight loss program, and for maintenance.

Animal and poultry fat

There’s a unique, pungent odour to a new bag of dry pet food — what is the source of that smell? It is most often rendered animal fat or vegetable fats and oils deemed inedible for humans. For example, used restaurant grease was rendered and routed to pet foods for several years, but a more lucrative market is now in biodiesel fuel production.

These fats are sprayed directly onto extruded kibbles and pellets to make an otherwise bland or distasteful product palatable. The fat also acts as a binding agent to which manufacturers add other flavour enhancers, such as “animal digests” made from processed by-products. Pet food scientists have discovered that animals love the taste of these sprayed fats. Manufacturers are masters at getting a dog or a cat to eat something.

What happened to the nutrients?

Cooking and other processing of meat and by-products used in pet food can greatly diminish their nutritional value, although cooking increases the digestibility of cereal grains and starchy vegetables.

Pet food manufacturers must “fortify” it with vitamins and minerals to make pet food nutritious. Why? Because their ingredients are not wholesome, their quality may be highly variable, and harsh manufacturing practices destroy many of the food’s nutrients.

Proteins are especially vulnerable to heat and become damaged, or “denatured,” when cooked. Because dry food ingredients are cooked twice — first during rendering and again in the extruder — problems are much more common than canned or homemade foods. Altered proteins may contribute to food intolerances, food allergies, and inflammatory bowel disease.