Just like all other living creatures, pet animals like dogs and cats require a combination of carbohydrates, fats, vitamins, proteins, minerals and water. This balance can be achieved by creating a balanced nutrition diet, providing sufficient calorie amounts to meet the daily needs of the animal for activity, growth and repair. While many pet food bags claim that they are "complete nutrition" foods, this claim means absolutely nothing unless the nutrients within are in a form that the pet can absorb into their system.

For example, since the hemicelluloses and celluloses of plant cells is not digestible in raw forms by dogs and cats, foods that are based on grains as a primary source of protein and carbohydrates absolutely must be processed in a manner that allows the nutrients to be extracted by the animal's digestive system. Not only do most major pet food companies work hard to balance their pet foods, but they also make every effort to provide ingredients in the most usable form possible.

Pet foods must contain vitamins and minerals in concentrations that are balanced as well. If there is too much of one mineral or vitamin, it may actually have interference against the absorption of another vitamin or mineral. Too little of a vital nutrient can interfere with vitamin or mineral use. Major pet food companies generally strive to provide the most balanced proportions of minerals and vitamins and other nutrients based on years of studies, and most pet food companies are constantly fine tuning their recipes to benefit the pets that their foods feed.

There are differences in the way that each pet food maker processes their food, and in the quality of ingredients they use, which can contribute to the balance of the food's nutrition. There are also finished product, storage and ingredient humidity and temperature changes that contribute to variation in the quality of the food. Some pet characteristics affect nutritional needs in food, including age, breed, activity level and level of health. More and more pet food companies are coming out with specialized foods for certain animal breeds, activity levels (overweight, sporting, working), size (small dog formula, large dog formula) and age level (senior formula, baby formula) and so on.

For some pets, a balanced nutrition requires an anti-allergen food, such as a duck and potato blend for dogs and cats with allergies to certain grains.

The best way to determine what the right balance is for your dog or cat is to speak to your veterinarian. Your veterinarian will have a good idea of the myriad of food choices out there, and will be able to recommend a food that will offer the right nutritional balance for your pet. It might be fruitful to explore a second opinion, or even a third, because some veterinarians give preferential treatments to certain food brands and may be making a somewhat biased decision.

However, slight differences in processing temperatures, in quality of the ingredients purchased, and storage humidity and temperature of ingredients of the finished product can cause variations in the quality that may affect a particular dog, a particular breed, or a particular line of dogs within a breed. In addition, some breeds or groups of breeds may require slightly different percentages of particular nutrients. Therefore, all dog foods are not perfect for all dogs, a factor that leads to the production of a plethora of different foods, claims, and processing methods.