Domestic dogs and cats are both members of the order Carnivora. Observations of feral canids indicate that their feeding habits are broad and include various parts of plants as well as both small and large prey. By comparison, cats do not show omnivorous feeding behaviors and have a requirement for specific animal-derived sources of nutrients, such as preformed vitamin A, arachidonic acid, and taurine. As a result, dogs are classified nutritionally as omnivores, while cats are classified as true carnivores.
Using appropriate feeding practices is one of the most important components of maintaining companion animal health. Nutritional management is also important as an integral part of both preventive health care and treatment protocols for medical and surgical patients, and ignoring nutritional needs can often be more detrimental to a dog or cat than the illness or injury for which it is being treated. Feeding an appropriately formulated and tested complete and balanced commercial diet is the simplest way to meet the nutritional requirements of dogs or cats. Numerous products are available, and many are formulated for specific life stages. However, dogs and cats can thrive eating a variety of commercial or appropriately formulated home-prepared foods.
Despite the wide availability of commercially complete and balanced diets for dogs and cats, malnutrition still occurs. Malnutrition is defined as an imbalance of nutrients and includes both nutrient deficiencies and nutrient excesses. In recent years, obesity has become the most common nutritional disorder encountered in small animal medicine. Obesity is a serious medical condition that can lead to a variety of related health problems as well as shortened life span.
Body weight in combination with body condition score (BCS) is used in many species to provide an estimate of nutritional adequacy and can help determine ideal body weight. BCS is a semiquantitative assessment of body composition that ranges from cachectic to severely obese. Physical examination, visual observation, and palpation are used to assign a BCS.
Two BCS systems exist for dogs and cats, a 5-point system and a 9-point system (see Table: Body Condition Score Scales a for Dogs and Cats). In a 9-point system, each unit increase in BCS above ideal represents body weight ~10%–15% greater than ideal body weight. For example, a dog or cat with a BCS of 7 is approximately 20%–30% heavier than its ideal weight.
Parameters used to assess BCS include evaluation of fat cover over the ribs, down the topline (waist), around the tailbase, and ventrally along the abdomen (abdominal tuck in front of hind legs). It is important to use both a visual assessment and palpation to assign a BCS (see Table: Parameters Used to Assess Body Condition Score).