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. Furthermore, the genome of the domestic dog is different from that of the wolf. For example, domestic dogs have three gene mutations associated with key roles in starch digestion and glucose absorptions that are different from those of wolves. As a result, the domestic dog shows an increased adaptation to carbohydrate-rich food, and from a nutritional standpoint, dogs are considered omnivores.
In contrast, cats have a relatively recent history of domestication, resulting in a more modest number of genome regions with strong signals of selection compared to dogs, and the predominant genotypic changes in cats reported to date are associated with behavioral modifications. Nonetheless, a lean, healthy, adult domestic cat can adapt to alterations in dietary macronutrient intake, resulting in the ability of the cat to successfully metabolize foods in which a moderate amount of calories are coming from carbohydrates.
Domestic cats also willingly eat diets containing plant-based nutrients, and they do have the ability to efficiently digest and absorb nutrients from plant origins, such as cooked starches, similar to dogs. However, from a nutritional standpoint, cats are still classified as obligate or true carnivores because they have metabolic adaptations that result in nutritional requirements that can only be met via a diet that includes animal tissues (ie, taurine, arginine, arachidonic acid, vitamin A, and vitamin D).
Feeding a complete and balanced diet, defined as a diet that provides all the nutrients a healthy dog or cat requires for a specific life stage, is critical for overall health in dogs and cats. Producing high-quality commercial pet food is a complex process, and it can often be difficult to find information on the pet food label that helps to determines quality. It is common for pet owners to focus heavily on ingredient lists when determining quality of pet food, such as looking for real meat listed first on the ingredient list or avoiding certain other ingredients. However, animals require nutrients, not ingredients, and two pet foods with very similar ingredient lists on the package label can differ in quality. It is also possible to sell a pet food that has never been fed to dogs or cats prior to becoming commercially available. Therefore, other considerations when selecting pet foods may include whether the company conducts research on their diets to support their claims and the safety of the food, or whether they employ a team of experts such as Board Certified Veterinary Nutritionists, experienced pet food formulators, animal nutritionists with an MS or PhD, food safety specialists, microbiologists, or toxicologists. The World Small Animal Veterinary Association (WSAVA) has more general, global recommendations for selecting pet foods. Numerous commercial diets are available; however, dogs and cats can also thrive eating a home-prepared diet formulated by a Board Certified Veterinary Nutritionist.
Body Condition Score Scales for Dogs and Catsa
Body condition | 5-Point scale | 9-Point scale |
|---|---|---|
Very thin | 1 | 1 |
Ideal weight | 3 | 4–5 (dogs); 5 (cats) |
Obese | 5 | 9 |
a The scale used should be noted in the record (eg, BCS = 4/5 or BCS = 4/9). | ||
Parameters Used to Assess Body Condition Score
Body Condition | Ribs | Overhead View | Side View | Tail Base |
|---|---|---|---|---|
Very thin | Ribs easily felt with no fat cover; prominent visibility of individual ribs in dogs with short hair coats | Accentuated hourglass shape | Severe abdominal tuck | Bones are raised with no tissue between the skin and bone |
Ideal | Ribs easily felt with slight fat cover; individual ribs not visible | Lumbar waist well-proportioned | Abdominal tuck present | Smooth contour but bones can be felt under a thin layer of fat |
Obese | Ribs difficult to feel under thick fat cover | Lumbar waist not visible | No abdominal tuck; fat hangs from abdomen | Thickened and difficult to feel under prominent layer of fat; dimple may be visible at tail base |
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 nutrient deficiencies and excesses, imbalance of essential nutrients, or impaired nutrient utilization. Malnutrition can occur in pets that are underweight or overweight. In recent years, obesity has become the most common nutritional disorder encountered in small animal medicine, and as of 2022, it was estimated that 59% of dogs and 61% of cats in the United States were overweight or obese(1). Obesity is a chronic inflammatory condition that can lead to a variety of related health problems as well as shortened lifespan.
Provided courtesy of the World Small Animal Veterinary Association (WSAVA). Available at the WSAVA Global Nutrition Committee Nutritional Toolkit website:http://www.wsava.org/nutrition-toolkit. Accessed December 12, 2019. Copyright Tufts University, 2014.
Provided courtesy of the World Small Animal Veterinary Association (WSAVA). Available at the WSAVA Global Nutrition Committee Nutritional Toolkit website:http://www.wsava.org/nutrition-toolkit. Accessed December 12, 2019. Copyright Tufts University, 2014.
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 fat composition that ranges from cachectic to severely obese. Although body condition score is inherently subjective, as long as specific criteria are applied, it is a reliable way of estimating body fat levels in dogs and cats. In those circumstances, the correlation between BCS in dogs and percentage of body fat is highly statistically significant (r = 0.90). Physical examination, visual observation, and palpation are used to assign a BCS.
Two BCS systems exist for dogs and cats, a 5-point scale and a 9-point scale. In a 5-point scale, each 1 point change in BCS above or below ideal (3) represents a 10% change in body fat, whereas with a 9-point scale, each 1 point change in BCS above or below ideal (5 for cats and 4–5 for dogs) represents a 5% change in body fat. For example, a dog with a BCS of 8/9 would have an increase in body fat ~15% above ideal, and a cat with a BCS of 2/5 would have a decrease in body fat 10% below ideal.
Percentage of body fat for ideal BCS is approximately 20%; however, in dogs, there are notable breed exceptions. For example, Greyhounds, and likely other sighthound breeds, have a higher muscle mass than other breeds. As a result, Greyhounds with a BCS of 5/9 have 7.2% body fat, as opposed to the average of 20%. Huskies and Rottweilers with a BCS of 5/9, however, have body fat levels of 31% and 32%, respectively.
Parameters used to assess BCS include evaluation of fat cover over the ribs, down the topline (waist), around the tail base, and ventrally along the abdomen (abdominal tuck in front of hind legs). It is important to use both a visual assessment and a palpation to assign a BCS; see the table of parameters used to assess BCS.
Although BCS is a good assessment of body fat and nutritional adequacy, it does not assess muscle mass. Muscle condition scoring (MCS) is done to assess muscle mass, which can also be an indication of nutritional adequacy. Aging is associated with loss of lean body mass, and as pets live longer, this is an important assessment to perform in older pets. A loss of muscle mass can be a sign of protein malnutrition or other medical condition that results in sarcopenia. There can also be disparities between BCS and MCS; therefore, simultaneously assessing BCS and MCS may detect a patient with a condition in which fat mass may have stayed the same or even increased while muscle mass decreased dramatically.
