The Manufacturing Process: How Pet Food Is Made
Although feeding trials are no longer required for a food to meet the requirements for labeling a food "complete and balanced," most manufacturers perform palatability studies when developing a new pet food. One set of animals is fed a new food while a "control" group is fed a current formula. The total volume eaten is used as a gauge for the palatability of the food. The larger and more reputable companies do use feeding trials, which are considered to be a much more accurate assessment of the actual nutritional value of the food. They keep large colonies of dogs and cats for this purpose, or use testing laboratories that have their own animals.
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 pet foods [such as Flint River Ranch pet 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.
Pet Food Labels
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?
Dr. Randy L. Wysong is a veterinarian and produces his own line of pet foods. A long-time critic of pet food industry practices, he said, "Processing is the wild card in nutritional value that is, by and large, simply ignored. Heating, cooking, rendering, freezing, dehydrating, canning, extruding, pelleting, baking, and so forth, are so commonplace that they are simply thought of as synonymous with food itself."7 Processing meat and by-products used in pet food can greatly diminish their nutritional value, but cooking increases the digestibility of cereal grains.
To make pet food nutritious, pet food manufacturers must "fortify" it with vitamins and minerals. Why? Because the ingredients they are using are not wholesome, their quality may be extremely variable, and the harsh manufacturing practices destroy many of the nutrients the food had to begin with.
Commercially manufactured or rendered meat meals and by-product meals are frequently highly contaminated with bacteria because their source is not always slaughtered animals. Animals that have died because of disease, injury, or natural causes are a source of meat for meat meal. The dead animal might not be rendered until days after its death. Therefore the carcass is often contaminated with bacteria such as Salmonella and Escherichia coli. Dangerous E. Coli bacteria are estimated to contaminate more than 50% of meat meals. While the cooking process may kill bacteria, it does not eliminate the endotoxins some bacteria produce during their growth and are released when they die. These toxins can cause sickness and disease. Pet food manufacturers do not test their products for endotoxins.
Mycotoxins — These toxins comes from mold or fungi, such as vomitoxin in the Nature's Recipe case, and aflatoxin in Doane's food. Poor farming practices and improper drying and storage of crops can cause mold growth. Ingredients that are most likely to be contaminated with mycotoxins are grains such as wheat and corn, cottonseed meal, peanut meal, and fish meal.
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
The idea of one pet food providing all the nutrition a companion animal will ever need for its entire life is a myth.
Cereal grains are the primary ingredients in most commercial pet foods. Many people select one pet food and feed it to their dogs and cats for a prolonged period of time. Therefore, companion dogs and cats eat a primarily carbohydrate diet with little variety. Today, the diets of cats and dogs are a far cry from the primarily protein diets with a lot of variety that their ancestors ate. The problems associated with a commercial diet are seen every day at veterinary establishments. Chronic digestive problems, such as chronic vomiting, diarrhea, and inflammatory bowel disease are among the most frequent illnesses treated. These are often the result of an allergy or intolerance to pet food ingredients. The market for "limited antigen" or "novel protein" diets is now a multi-million dollar business. These diets were formulated to address the increasing intolerance to commercial foods that animals have developed. The newest twist is the truly "hypoallergenic" food that has had all its proteins artificially chopped into pieces smaller than can be recognized and reacted to by the immune system.
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.
Pet food formulas and the practice of feeding that manufacturers recommend have increased other digestive problems. Feeding only one meal per day can cause the irritation of the esophagus by stomach acid. Feeding two smaller meals is better.
Feeding recommendations or instructions on the packaging are sometimes inflated so that the consumer will end up purchasing more food. However, Procter & Gamble allegedly took the opposite tack with its Iams and Eukanuba lines, reducing the feeding amounts in order to claim that its foods were less expensive to feed. Independent studies commissioned by a competing manufacturer suggested that these reduced levels were inadequate to maintain health. Procter & Gamble has since sued and been countersued by that competing manufacturer, and a consumer complaint has also been filed seeking class-action status for harm caused to dogs by the revised feeding instructions.
Urinary tract disease is directly related to diet in both cats and dogs. Plugs, crystals, and stones in cat bladders are often triggered or aggravated by commercial pet food formulas. One type of stone found in cats is less common now, but another more dangerous type has become more common. Manipulation of manufactured cat food formulas to alter the acidity of urine and the amount of some minerals has directly affected these diseases. Dogs also form stones as a result of their diet.
History has shown that commercial pet food products can cause disease. An often-fatal heart disease in cats and some dogs is now known to be caused by a deficiency of the amino acid taurine. Blindness is another symptom of taurine deficiency. This deficiency was due to inadequate amounts of taurine in cat food formulas, which itself occurred because of decreased amounts of animal proteins and increased reliance on carbohydrates. Cat foods are now supplemented with taurine. New research suggests that supplementing taurine may also be helpful for dogs, but as yet few manufacturers are adding extra taurine to dog food. Inadequate potassium in certain feline diets also caused kidney failure in young cats; potassium is now added in greater amounts to all cat foods.
Rapid growth in large breed puppies has been shown to contribute to bone and joint disease. Excess calories and calcium in some manufactured puppy foods promoted rapid growth. There are now special puppy foods for large breed dogs. But this recent change will not help the countless dogs who lived and died with hip and elbow disease.
There is also evidence that hyperthyroidism in cats may be related to excess iodine in commercial pet food diets.9 This is a new disease that first surfaced in the 1970s, when canned food products appeared on the market. The exact cause and effect are not yet known. This is a serious and sometimes terminal disease, and treatment is expensive.
Many nutritional problems appeared with the popularity of cereal-based commercial pet foods. Some have occurred because the diet was incomplete. Although several ingredients are now supplemented, we do not know what ingredients future researchers may discover that should have been supplemented in pet foods all along. Other problems may result from reactions to additives. Others are a result of contamination with bacteria, mold, drugs, or other toxins. In some diseases the role of commercial pet food is understood; in others, it is not. The bottom line is that diets composed primarily of low quality cereals and rendered meat meals are not as nutritious or safe as you should expect for your cat or dog.On to Page 3: What Consumers Can Do