We understand that as the sole source of nutrition for our pets, pet food makers bear an incredible responsibility to provide dogs and cats with safe, high quality and complete nutrition.
Most pet food is designed to be “complete and balanced,” which means each serving is a complete meal and provides total nutrition. As such, pet foods are made with carefully prepared recipes crafted by experts in companion animal nutrition, and veterinary scientists.
Nutrients can be generally grouped into four categories: proteins, fats, carbohydrates, and vitamins, minerals and independent amino acids. Veterinary researchers have identified between 42 and 48 essential nutrients for cats and dogs. These are provided by the ingredients used in a given pet food recipe.
In “Ingredients: Where Pet Food Starts,” Dr. Angele Thompson, one of the world’s foremost authority on pet food nutrition takes us through an example of a complete and balanced dry dog food containing 42 ingredients. An excerpt is provided here:
Sources of Vitamins and Minerals
A commonly asked question is: what are all those chemical sounding names? In most cases, they are the vitamin and mineral sources. The AAFCO Nutrient Profiles contain 23 and 25 essential vitamins and minerals for dogs and cats, respectively. Usually they are provided to the product via a prepared “packet” called a premix. This is the multi-vitamin/mineral of the complete food. While vitamins and minerals are added in very small amounts, they account for close to half of the ingredients in a pet food, and are the longest part of the ingredient statement. Removing the vitamins and minerals from the original 42 ingredients listed in the ingredient statement in Table 2A, the list now contains 16 ingredients as shown in Table 2B. There are only two or three ‘chemical sounding’ names remaining in the list. Two of those are essential amino acids: lysine and methionine.
Sources of Protein and Amino Acids
The three largest nutrient components of pet food are protein, carbohydrate and fat. There are many combinations of protein sources that deliver a balanced amino acid profile. Think of the spectrum of combinations between the human who eats steak and the vegan. Both can get a proper balance of amino acids in their diets through the use of various ingredients. The protein sources in the example are: poultry by-product meal, corn gluten meal, meat and bone meal, and soybean meal, with some contribution of protein from whole corn, whole wheat, barley, rice, animal digest and the amino acids. This mixture of ingredients provides the amino acids not only for the desired amount of crude protein (in this case, 21% minimum), but for the proper balance of essential amino acids. In a wet product, typical protein sources would be meats and meat by-products, poultry and poultry by-products and fish and fish by-products. Plant protein sources are sometimes used in wet foods but to a lesser extent.
Sources of Carbohydrate
Carbohydrate is a broad category of compounds from sugars to starches to oligosaccharides to celluloses. While carbohydrates are not considered essential for dogs and cats, pets do have a physiologic need for carbohydrates. Carbohydrates supply glucose for cellular energy, thus sparing protein, which would otherwise need to be converted to glucose, for other functions in the body. Both dogs and cats can digest and metabolize carbohydrates. Cats, despite being classed as strict carnivores, can utilize starch as a glucose source. Carbohydrates also provide the fiber in pet diets. Fiber is a subcategory of carbohydrates, but it also describes a very broad group of compounds. Fiber sources are important for gut health and proper gut motility. In the example in Table 2, the carbohydrate sources are whole grain corn and brewers rice, barley, and whole grain wheat. Other sources of digestible carbohydrates in pet foods include: various grain flours, brown rice, oats, sorghum, and potatoes. Some sources of fiber include: wheat bran, rice bran, soybean hulls, beet pulp, powdered cellulose, chicory root, inulin, and fructooligosaccharides.
Sources of Fatty Acids
The fat in the example is supplied by animal fat, produced via the rendering process. Additional fat comes from the poultry by-product meal and corn, with smaller amounts coming from meat and bone meal, wheat, soybean meal, and animal digest. This mixture provides a range of fatty acids including the essential unsaturated fatty acid, linoleic acid. Other commonly used fat sources are: vegetable oils for linoleic acid, plus fish oil and flaxseed oil for omega-3 fatty acids.
Oxygen is the enemy of fatty acids, particularly unsaturated fatty acids. When oxygen destroys fatty acids, damaging free radicals are formed and the product is said to be oxidized or rancid. The function of the mixed-tocopherols in pet foods is to prevent that oxidation from occurring, in other words, they are the antioxidants in the product. Some people have negative beliefs about antioxidants; however, some type of antioxidant (preservation) system is needed in all dry products. This is because oxygen destroys the unsaturated fatty acids first. A rancid product is deficient in critical nutrients, contains free radicals and probably has a bad taste/aroma that will cause the pet to reject the food. Wet products do not need preservatives because they are hermetically sealed and the oxidation process is halted until the package is opened.
The Rest of the Ingredients
Four ingredients remain in the dog food example in Table 2B that still need an explanation: animal digest, garlic oil and the two coloring agents – Red 40 and Yellow 5. The animal digest and garlic oil are part of the palatability/aroma system.
Animal digest is defined by AAFCO as shown in Table 1. A simple analogy would be that it is like giblet gravy. The most common ingredient in animal digest is liver because of its great enzymatic capacity, but washed chicken viscera (organs) are also used. The enzymes breakdown the proteins and fats resulting in a mixture of free amino acids and fatty acids that is quite tasty to the animal. The digest is heated to stop the chemical reaction and to sterilize it. It might be used in liquid form or spray dried and used as a dry powder to coat onto the outside of expanded dried kibbles.
The final ingredients shown in the example are two food dyes. While the dyes are not nutrients for the pet, they are used to please the eye of the owner. The owner has to buy the food and feel good about it in order for it to get into the pet’s bowl. While some pet owners prefer foods with no artificial colors, others actually prefer foods with colors added. The lowest level of dye is used to deliver the desired color. In this case the colors are FD&C certified colors, while other GRAS colors can include natural colors such as beet powder. All allowed colorants used in pet foods have been documented to be safe.
 Topics in Companion Animal Medicine
Controversies in Small Animal Nutrition: Pet Food Safety
Volume 23 Number 3 August 2008 Pages 127-132