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 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, de characterizing 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.