Pet Food Quality

Pet food quality is difficult to define but is easily measured by the ultimate judge, the pets.

Consumers often evaluate quality on the basis of ingredients, guaranteed analysis, palatability, physical form and appearance of ration, etc. While these are important factors in assessing the quality of a pet food, one should use caution in relying solely on one or two of the above-mentioned factors when evaluating pet foods.

Palatability, for example, is very important. Obviously the ration must be palatable enough for the pet to consume sustaining quantities of nutrition; however, high palatability levels do not necessarily equal high quality or high levels of nutrition. It’s best to evaluate a pet food's quality based on a variety of factors, including how the pet performs, rather than relying on just one or two components of the diet.

Nutritional Requirements

Dogs and cats require certain nutrient requirements to support growth, gestation, lactation and general maintenance. About 40 specific nutrients have been identified as required by dogs and cats. A nutritional expert subcommittee of the Association of American Feed Control Officials (AAFCO) has established these requirements. This committee is composed of nutritionists and veterinarians from industry, government and universities.

All pet foods must meet these requirements or be labeled as snacks, treats or supplemental feeding in order to be registered for sale. However, differences can exist between registered pet foods due to variances in ingredient consistency, quality, manufacturing practices, formulation (balance of nutrients) and product forms.

Basic Requirements


Proteins are made up of amino acids. Protein is required in the body for growth, breeding and maintenance. There are a variety of quality protein sources for pets, including animal and plant sources.

Protein is expressed on the label guaranteed analysis as "Crude Protein." High crude protein guarantees do not ensure a high digestible protein level or a correct amino acid balance. Protein deficiency results in depressed food intake, growth retardation and even death.

Several factors can change the amount of protein required such as digestibility, amino acid composition, availability, energy level of the diet and life stage of the pet. Amino acid levels must be in balance for optimum growth and health.

Essential Amino Acids

For both dogs and cats. Must be supplied in the diet.

  • Arginine
  • Histidine
  • Isoleucine
  • Threonine
  • Lysine
  • Methionine
  • Phenyulallnine
  • Taurine*
  • Tryptophan
  • Valine
  • Leucine

*Cats only.

Crude Protein – total amount of protein, determined by the nitrogen content.

Digestible Protein – amount of protein that is available to the pet.


Energy (fats and carbohydrates) is required by all pets for growth, reproduction and maintenance. An indication of excessive energy intake is obesity, while energy deficient diets generally result in a loss of body weight.

Proper formulation of pet foods as it relates to energy is a complicated matter. Ration intake, fat and carbohydrate ingredient levels, digestibility and metabolizable energy ingredient levels, pet size, activity level and life stage are all critical factors in determining the correct dietary energy level.

It has been shown that most pets will adjust their food intake to meet their energy requirement. It is critical, therefore, that high caloric-dense diets be formulated with higher protein, mineral and vitamin levels to compensate for the lower ration intake. Lactation and extreme activity levels such as sled dog teams can greatly increase the energy requirement of the pet.


Fat is a concentrated source of energy and provides essential fatty acids. Fatty acids (now commonly referred to as omega fats) are important in cell membranes and metabolic regulation. An important essential fatty acid is linoleic acid. Linoleic acid levels appear to be related to healthy skin and hair coat. Fat serves as a carrier of fat-soluble vitamins and lends palatability to dog foods.


All animals require carbohydrates (glucose) to supply energy for organs and the central nervous system. The cooking of starches (grains) enhances their availability. The process of extrusion increases the digestibility of carbohydrate sources such as grains, due to the cooking process. Fiber is not generally considered a source of energy for simple-stomached animals, including dogs and cats, although fiber is essential and beneficial in the diet. Fiber reduces gastrointestinal transit time and as a result, tends to be a stool conditioner.


Gross Energy (GE) – Total combustible energy

Digestible Energy (DE) – The difference between the gross energy consumed and the gross energy in the feces.

Metabolizable Energy (ME) – The difference between digestible energy consumed and the gross energy in the urine. Metabolizable energy is a valid expression of the energy available to pets and is often used as a basis of comparison. Most metabolizable energy are calculated values.


Minerals are required in the diet of pets for a variety of reasons, primarily those related to skeletal functions. The total mineral content of a diet is sometimes referred to as the ash content. Ash is a term used to describe the non-combustible portion of the diet remaining after a sample is burned at 600° F for 120 minutes. Minerals are inorganic compounds that make up major parts of the teeth, claws and skeleton of animals.

Due to the variety of breeds, environmental conditions, interaction with other ingredients, biological availability and other variables, most mineral requirements for pets are estimated values obtained from experience with diets that have resulted in acceptable performance in dogs and cats.

The major minerals are calcium and phosphorus. The individual levels, ratio to each other and ratio to energy content are all important. Calcium and phosphorus are often discussed together due to their close metabolic and nutritional association.

Calcium to phosphorus ratios of 1.2:1 to 1.4:1 are considered acceptable for dogs, while a 0.9:1 to 1.1:1 ratio is considered acceptable for cats. These ratios are not totally independent values as other minerals and some vitamins have been shown to interact with the absorption and utilization of calcium and phosphorus.

Additional minerals important in pet foods include magnesium, potassium, sodium, chlorine, iron, copper, manganese, zinc, iodine, selenium, cobalt, sulfur and other trace minerals. Signs of deficiencies or toxicities vary widely with the specific mineral in question and other factors such as breed, activity level and environment.

Mineral deficiencies or toxicities are rare with most commercially prepared pet foods but can show up with home-prepared diets or diets that are over-supplemented or otherwise altered.


Vitamins have been recognized as essential nutrients for over 60 years. Despite this extensive history, precise information on requirements have not been established for every vitamin. Vitamins can be generally defined as substances that are involved in key roles to help maintain body functions and the life process.

Vitamins are divided into two classifications; fat-soluble (A, D, E & K) and water-soluble (C, niacin, riboflavin and others). Fat-soluble vitamins can be stored in the liver and adipose tissue. Water-soluble vitamins are not stored as a general rule and must be included in the diet on a regular basis.

The water-soluble vitamins are involved in a wide variety of important body functions including proper growth patterns. Water-soluble and fat-soluble vitamins can be unstable and their destruction can be promoted by heat, light, oxidation and moisture.

Vitamin deficiency and toxicity symptoms vary with the specific vitamin in question and other factors such as breed, activity level and environment. It is generally recognized that vitamin requirements are related to energy requirements. As energy intake increases due to lactation, for example, intake of vitamins will also go up as a result of an increase in the total ration consumption. Vitamins can be oversupplied, especially in cases of over-supplementation of the diet or excessive use of vitamin-rich treats.

Vitamins that have been recognized to have important functions include A, D, E, K, thiamine, riboflavin, pantothenic acid, niacin, B6, folacin, biotin, B12, choline and vitamin C. Recommendations for vitamin levels in pet foods are based on various studies and trials as well as experience with diets that have resulted in acceptable performance in dogs and cats.


Water is the most important nutrient as it is vital to the functioning of all living cells. The non-fat component of mammals contains about 73 percent water. Dogs and cats obtain water in liquid form, from food and from metabolism. The body water content is fairly constant, with intake balanced by loss, principally through urine, lungs, skin, feces and in the bitch or queen milk.

Water requirements vary with activity, environment, type of food and other factors. Fresh, clean water should be available to pets at all times (some dogs may overconsume water, particularly if it is cold water, following extreme exercise). Individual pet's water intake will usually range from two to three times the dry matter intake. During lactation, hot weather or severe exertion, water intake may reach four or more times dry matter intake.

Minimum Feline Nutritional Requirements (As Fed Basis)

AAFCO Nutrient Profiles* (2011)

Nutrient Major Function Reproduction Maintenance
Protein Growth/Maintenance 27.00% 23.40%
Fat Energy/Skin/Coat 8.10% 8.10%
Linoleic Acid Skin/Hair/Coat 0.45% 0.45%
Calcium Bones/Teeth/Muscles 0.90% 0.54%
Phosphorus Bones/Teeth/Muscles 0.72% 0.45%
Potassium Regulate Body Fluids 0.54% 0.54%
Sodium Chloride Regulate Body Fluids 0.45% 0.045%
Magnesium Bones & Teeth 0.072% 0.036%
Iron Blood 72.00 mg/kg 72.00 mg/kg
Copper Blood 4.5 mg/kg 4.5 mg/kg
Manganese Maintenance 6.75 mg/kg 6.75 mg/kg
Zinc Reproduction 67.5 mg/kg 67.5 mg/kg
Iodine Thyroid 0.315 mg/kg 0.315 mg/kg
Selenium Muscles 0.09 mg/kg 0.09 mg/kg
Vitamin A Eyes/Hair/Coat 8,100.00 IU/kg 4,500.00 IU/kg
Vitamin D Vigor/Bones/Teeth 675.00 IU/kg 450.00 IU/kg
Vitamin E Reproduction/Growth 27.00 IU/kg 27.00 IU/kg
Vitamin B12 Blood 0.018 mg/kg 0.018 mg/kg
Folic Acid Growth Maintenance 0.72 mg/kg 0.72 mg/kg
Biotin Metabolism 0.063 mg/kg 0.063 mg/kg
Thiamine (Vit. B1) Nerves/Digestion/Appetite 4.5 mg/kg 4.5 mg/kg
Riboflavin (Vit. B2) Eyes/Skin/Nerves 3.6 mg/kg 3.6 mg/kg
Pyridoxine (Vit. B6) Blood 3.6 mg/kg 3.6 mg/kg
Pantothenic Acid Growth/Appetite 4.5 mg/kg 4.5 mg/kg
Niacin Nerves/Hair/Coat 54.00 mg/kg 54.00 mg/kg
Choline Liver/Kidneys 2,160.00 mg/kg 2,160.00 mg/kg

*Minimum requirements established for the cat. 90% Dry Matter. Data from American Association of Feed Control Officials.

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Listed below are the official and tentative definitions of feed ingredients (abbreviated) as established by the Association of American Feed Control Officials (AAFCO) for some of the major ingredients most commonly included in pet foods.

Meat and Bone Meal is the rendered product from mammal tissues, including bone, exclusive of blood, hair, hoof, horn, hide trimmings, manure, stomach and rumen contents, except in such amounts that may occur unavoidably in good processing practices. It shall not contain added extraneous materials not provided for in this definition. It shall contain a minimum of 4.0 percent phosphorus (P) and the calcium (Ca) level shall not be more than 2.2 times the actual phosphorus (P) level.

Meat Meal is the rendered product from mammal tissues, exclusive of blood, hair, hoof, horn, hide trimmings, manure, stomach and rumen contents except in such amounts that may occur unavoidably in good processing practices. It shall not contain added extraneous materials not provided for by this definition. The calcium (Ca) level shall not exceed the actual level of phosphorus (P) by more than 2.2 times.

Poultry By-Product Meal consists of the ground, rendered, clean parts of the carcass of slaughtered poultry, such as necks, feet, undeveloped eggs, and intestines, exclusive of feathers, except in such amounts that may occur unavoidably in good processing practices. The calcium (Ca) level shall not exceed the level of phosphorus (P) by more than 2.2 times.

Poultry Meal is the dry rendered product from a combination of clean flesh and skin with or without accompanying bone, derived from the parts of whole carcasses of poultry or a combination thereof, exclusive of feathers, head, feet and entrails. It shall be suitable for use in animal food. If it bears a name descriptive of its kind, it must correspond thereto, i.e., turkey meal.

Poultry is the clean combination of flesh and skin with or without accompanying bone, derived from the parts of the whole carcass of poultry or a combination thereof, exclusive of feathers, head, feet and entrails.

Fish Meal is the clean, dried, ground tissue of undecomposed whole fish or fish cuttings, either or both, with or without the extraction of part of the oil. It must contain not more than 10 percent moisture.

Animal Liver bears a name descriptive of its kind; it must correspond thereto. Meal is obtained by drying and grinding liver from slaughtered animals.

Whole Dried Eggs are eggs, from which the moisture has been removed. They may or may not include the shell.

Animal Fat is obtained from the tissues of mammals and/or poultry in the commercial process of rendering or extracting. It consists predominantly of glyceride esters of fatty acids and contains no additions of free fatty acids or other materials obtained from fats. It must contain not less than 90 percent total fatty acids, not more than 2.5 percent unsaponifiable matter and not more than 1 percent insoluble matter. If the product bears a name descriptive of its kind or origin, i.e., "tallow," "lard," "grease," it must correspond thereto. If an antioxidant is used, the common name or names must be indicated, followed by the word "preservative(s)."

Dried Fish Protein Digest is the dried enzymatic digest of clean, undecomposed, whole fish or fish cuttings using the enzyme hydrolysis process. The product must be free of bones, scales and undigested solids with or without the extraction of part of the oil. It must contain not less than 80 percent protein and not more than 10 percent moisture.

Animal Digest is a material which results from chemical and/or enzymatic hydrolysis of clean and undecomposed animal tissue. The animal tissues used shall be exclusive of hair, horns, teeth, hooves and feathers, except in such trace amounts as might occur unavoidably in good factory practice and shall be suitable for animal feed. If it bears a name descriptive of its kind or flavor(s), it must correspond thereto.

Ground Corn is the entire kernel ground or chopped. It must contain not more than 4 percent foreign materials.

Kibbled Corn is obtained by cooking cracked corn under steam pressure and extruding from an expeller or other mechanical pressure device.

Corn Gluten Meal is the fried residue from corn after the removal of the larger part of the starch and germ, and the separation of the bran by the process employed in the wet milling manufacture of cornstarch or syrup or by enzymatic treatment of the endosperm.

Soybean Meal, Dehulled Solvent Extracted is obtained by grinding the flakes remaining after removal of most of the oil from dehulled soybeans by a solvent extraction process. It must contain not more than 3.5 percent crude fiber and not more than 12.0 percent moisture. When listed as an ingredient in a manufactured feed, it may be identified as "Dehulled Soybean Meal."

Soybean Meal, Solvent Extracted is the product obtained by grinding the flakes, which remain after removal of most of the oil from soybeans by a solvent extraction process. It must contain not more than 7.0 percent crude fiber and not more than 12.0 percent moisture. The words "Solvent Extracted" are not required when listing as an ingredient in a manufactured feed.

Wheat Flour consists principally of wheat flour together with fine particles of wheat bran, wheat germ and the offal from the “tail of the mill.” This product must be obtained in the usual process of commercial milling and must not contain more than 1.5 percent crude fiber. Semolina wheat flour is used as an ingredient in pasta.

Wheat Germ Meal consists chiefly of wheat germ together with some bran and middlings or shorts. It must contain not less than 25 percent crude protein and 7 percent crude fat.

Wheat Middlings consist of fine particles of wheat bran, wheat shorts, wheat germ, wheat flour and some of the offal from the "tail of the mill." This product must be obtained in the usual process of commercial milling and must contain not more than 9.5 percent crude fiber.

Brewers Rice is the small fragments of rice kernels that have been separated from the larger kernels of milled rice.

Dried (Dry) Whey is the product obtained by removing water from whey. It contains not less than 11 percent protein nor less than 61 percent lactose.

Yeast Culture is the dried product composed of yeast and the media on which it was grown, dried in such a manner as to preserve the fermenting activity of the yeast.

Beet Pulp, Dried, Plain is the dried residue from sugar beets which has been cleaned and freed from crowns, leaves and sand,, and which has been extracted in the process of manufacturing sugar.

Cereal Food Fines consists of particles of breakfast cereals obtained as a by-product of their processing.

Ground Rice is the entire product obtained in grinding the whole rice grain including the hulls.

Dried Skim Milk is the residue obtained by drying defatted milk. It contains 8 percent maximum moisture.

Lecithin is a specific phospholipid. The principal constituent of crude phospholipids derived from oil-bearing seeds.

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It is important to know that palatability does not always infer quality. Also, palatability tests are sometimes very misleading in that opposite results can be achieved using the same products at the same independent testing facilities. Some facts to keep in mind regarding palatability are as follows:

  1. Palatability is only one factor among many factors making up "quality" pet food. Consistency, nutritional adequacy, stools, color, etc., are just some of the others.
  2. Hubbard Life continually tests products for palatability so as to assure the dog or cat will eat enough of the product to gain the nutrients demanded for the daily activity of the animal.
  3. Products with inadequate nutritional value can be "doctored up" to make the dog or cat want to eat the product.
  4. Use caution. Given enough palatability tests, even an inferior product will occasionally show higher palatability than a superior product.

The point is that palatability is only one of many, perhaps equally, or more important factors, with regard to pet nutrition. The product must be palatable enough to the animal so they will consume enough to maintain growth and lead a healthy, happy life.

It is a mistake to assume because a product's palatability is better than another’s that it is of superior quality. A chocolate candy bar to a child is more palatable than lettuce, carrots and fruit, but this does not mean the chocolate bar is of better "quality" and the chocolate bar is certainly not more nutritious.

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Pet Food Labels

Pet food labels are often used to judge the quality of pet foods. All pet foods must meet AAFCO's label regulations and conform to the U.S. "Fair Packaging and Labeling Act."

Even though a pet food label may be similar to another, the pet may not perform as well due to the differences in digestibility. Pet food manufacturers must list the crude protein (min), crude fat (min), crude fiber (max) and the moisture level (max). They have the option to list additional guarantees after moisture. The ingredients must be listed in descending order by weight.

References to the quality or grade of ingredient are not permitted. The label of a pet food must also identify the name and address of the manufacturer, packer or distributor of the pet food and package net weight as well as feeding instructions.