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Additives and Preservatives
Many chemicals are added to commercial pet foods to improve the taste, stability, characteristics, or appearance of the food. Additives provide no nutritional value. Additives include emulsifiers to prevent water and fat from separating, antioxidants to prevent fat from turning rancid, and artificial colors and flavors to make the product more attractive to consumers and more palatable to their companion animals.

Adding chemicals to food originated thousands of years ago with spices, natural preservatives, and ripening agents. In the last 40 years, however, the number of food additives has greatly increased.

All commercial pet foods contain preservatives. Some of these are added to ingredients or raw materials by the suppliers, and others may be added by the manufacturer. Because manufacturers need to ensure that dry foods have a long shelf life to remain edible after shipping and prolonged storage, fats included in pet foods are preserved with either synthetic or "natural" preservatives. Synthetic preservatives include butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT), propyl gallate, propylene glycol (also used as a less-toxic version of automotive antifreeze), and ethoxyquin. For these antioxidants, there is little information documenting their toxicity, safety, or chronic use in pet foods that may be eaten every day for the life of the animal.

Potentially cancer-causing agents such as BHA, BHT, and ethoxyquin are permitted at relatively low levels. The use of these chemicals in pet foods has not been thoroughly studied, and long term build-up of these agents may ultimately be harmful. Due to questionable data in the original study on its safety, ethoxyquin's manufacturer, Monsanto, was required to perform a new, more rigorous study. This was completed in 1996. Even though Monsanto found no significant toxicity associated with its own product, in July 1997, the FDA's Center for Veterinary Medicine requested that manufacturers voluntarily reduce the maximum level for ethoxyquin by half, to 75 parts per million. While some pet food critics and veterinarians believe that ethoxyquin is a major cause of disease, skin problems, and infertility in dogs, others claim it is the safest, strongest, most stable preservative available for pet food. Ethoxyquin is only approved for use in human food for preserving spices, such as cayenne and chili powder, at a level of 100 ppm -- but it would be very difficult to consume as much chili powder every day as a dog would eat dry food. Ethoxyquin has never been tested for safety in cats.

Some manufacturers have responded to consumer concern, and are now using "natural" preservatives such as Vitamin C (ascorbate), Vitamin E (mixed tocopherols), and oils of rosemary, clove, or other spices, to preserve the fats in their products. Other ingredients, however, may be individually preserved. Fish meal, and some prepared vitamin mixtures used to supplement pet food, contain chemical preservatives. This means that your companion animal may be eating food containing several types of preservatives. Not all of these are required to be disclosed on the label. However, due to consumer pressure, preservatives used in fat are now required to be listed on the label.

While the law requires studies of direct toxicity of these additives and preservatives, they have not been tested for their potential synergistic effects on each other once ingested. Some authors have suggested that dangerous interactions occur among some of the common synthetic preservatives.4 Natural preservatives do not provide as long a shelf life as chemical preservatives, but they do not carry the unanswered questions about their safety.

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.

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.

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. The "all meat" product is covered by AAFCO's "95% Rule": "When an ingredient or a combination of ingredients derived from animals, poultry, or fish constitute 95% or more of the total weight of all ingredients of a pet food, the name or names of such ingredient(s) may form part of the product name of the pet food; provided that where more than one ingredient is part of such product name, then all such ingredient names shall be in the same size, style, and color print. For the purpose of this provision, water sufficient for processing shall be excluded when calculating the percentage of the named ingredient(s). However, such named ingredient(s) shall constitute at least 70% of the total product."6 Because all-meat diets are not nutritionally balanced, they are uncommon today.

The "dinner" product is defined by the 25% Rule: "When an ingredient or a combination of ingredients constitutes at least 25% but less than 95% of the total weight of all ingredients of a dog or cat food mixture, the name or names of such ingredient or ingredients may form a part of the product name of the pet food if each of the ingredients constitute at least 3% of the product weight excluding water used for processing and only if the product name also includes a primary descriptive term such as 'dinner', 'platter,' or similar designation so that the product name describes the contents of the product in accordance with an established law, custom or usage or so that the product name is not misleading. If the names of more than one ingredient are shown, they shall appear in the order of their respective predominance by weight in the product. All such ingredient names and the primary descriptive term shall be in the same size, style and color print. For the purpose of this provision, water sufficient for processing shall be excluded when calculating the percentage of the named ingredient(s). However, such named ingredient(s) shall constitute at least 10% of the total product."7

The "flavor" product is formulated to have a specific flavor: "No flavor designation shall be used on a pet food label unless the flavor is detected by a recognized test method, or is one the presence of which provides a characterisitic distinguishable by the pet. Any flavor designation on a pet food label must either conform to the name of its source as shown in the ingredient statement or the ingredient statement shall show the source of the flavor. The word flavor shall be printed in the same size type and with an equal degree of conspicuousness as the ingredient term(s) from which the flavor designation is derived. Distributors of pet food employing such flavor designation or claims on the labels of the product distributed by them shall, upon request, supply verification of the designated or claimed flavor to the appropriate control official."8 In essence, the "flavor rule" allows a food to be labeled as "beef flavor" without actually containing any beef meat at all.

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