Supplementation of diets may be necessary due to dietary imbalances or because of disease-specific therapeutic benefits of the supplement.

Obesity is the most important malnutrition of companion animals. It can be a disabling medical condition when moderate to severe in scope. At prevalence rate estimates of 10-40%, obesity must be considered a significant hazard to dogs and cats.

Some owners prefer to prepare homemade foods – feel less guilty and have impression of preparing a "real meal" that is "more natural" and "more traditional".

Veterinarians, veterinary technicians, and the general public are inundated with information, some accurate and some not, on pet nutrition.

Pet food sales in the United States exceed 17 billion dollars. Veterinarians and veterinary staff are – and should be – a valuable source for nutritional recommendations.

Foods, whether for human or animal consumption, are supposed to provide nutrients for maintenance of health; however, situations arise where the food may be source of the problem.

Therapeutic diets represent another aspect of treatment of specific diseases in addition to conventional therapy. These diets are designed for one or more diseases and formulated to contain a nutrient composition that may be of benefit in treating these diseases.