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 gage 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 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 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 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, de-characterizing agents, or trace amounts of preservatives and condiments." Products containing multiple ingredients are covered by AAFCO Regulation PF 3(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," "entrée," 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. 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 next page.