Domestication and use of dogs and cats as companions may have modified eating patterns of these animals to varying extents. Easier access to food and consistency of food quality has led to increased food consumption and the possibility of decreased energy expenditure overall. Hence, there is greater risk of obesity. At the same time, longevity of companion animals has also increased and, along with it, the emergence of other chronic progressive diseases such as osteoarthritis, cancer, and immune and cognitive disorders. Healthy dogs and cats eat a variety of foods. During a 24-hr period, most dogs will eat 1–3 meals, whereas most cats will eat frequent small meals, as many as 18 a day.
Although odor, consistency, taste, and learned dietary habits determine which foods a dog will eat, most dogs are indiscriminate eaters. Finicky, begging dogs have learned such behaviors. Likewise, odor, consistency, taste, and learned dietary habits determine which foods a cat prefers, but how much a cat will eat is affected by factors such as noises, lights, food containers, the presence or absence of people or other animals (including other cats), physiologic state, and disease. Cats can and will refuse to eat to the point of starving themselves under stressful conditions. These cats are at risk of developing hepatic lipidosis, which can be fatal if not treated early and aggressively.
Some dogs and cats have adequate appetite controls and maintain an optimal body condition, even with dietary changes. By contrast, other dogs and cats overeat, consume excessive calories, and become obese. The thickness of the fat layer over the rib cage and pelvic bones is a good indicator of obesity, as is regular body condition scoring over time (see Table: Body Condition Score Scales a for Dogs and Cats and see Table: Parameters Used to Assess Body Condition Score).
Dietary modifications are required by changes in life stage, environment, body weight and condition, and disease. Energy density varies from 2,500 to >5,000 kcal/kg dry matter for dog foods and from 3,000 to >5,000 kcal/kg dry matter for cat foods. Therefore, general feeding recommendations cannot be given for all dogs and cats on any particular food. Instead, feeding recommendations should be individualized. The best feeding method is one that maintains optimal body weight and condition, bearing in mind that disease conditions may require dietary changes.
When a dietary change is necessary, it should not be done abruptly. New food should be introduced gradually throughout 5–7 days. Also, it is better to offer slightly less than the calculated new food amount. Overindulgence and abrupt changes are frequently the inciting cause of GI disorders that may ultimately lead to diet refusal. In dogs, the new food should be introduced slowly by replacing 25% more of the old food every day or two until the new diet makes up the entire amount fed. Cats can easily become habituated to a particular food and may resist any dietary change. In cats, new food should also be introduced slowly. Some cats have definitive preferences for dry food, whereas others prefer the same food moistened or canned.
If the dog or cat is to be switched from a canned to a dry diet, it may be useful to moisten the product by adding sufficient warm water, and the food can be warmed to release odors and flavors that encourage consumption. Dry-matter digestibilities are 60%–90% for dog food and 75%–90% for cat food because of ingredient quality, crude-fiber content, processing, and level of intake. Small, formed, brown feces suggest high nutrient digestion and absorption, while large volumes of pale feces indicate less dietary utilization.
After a dog has reached ~90% of its expected adult weight, a diet less nutrient dense than the growth diet is recommended. The dietary goal is to maintain optimal body weight and condition for that particular dog. Some adult dogs can be fed free choice, but most cannot without becoming obese. The best feeding regimen to use in most adult dogs to prevent obesity is portion-controlled feeding, eg, feeding two premeasured meals at regular times each day. Most dogs will eat all their food immediately, but some dogs will graze throughout the day.
Many owners feed treats and snacks, which are often an important aspect of the human-animal bond. Complete and balanced treat products that use low-fat, high-fiber ingredients are available. However, most treats are not complete and balanced; therefore, to prevent nutrient deficiencies, the total daily amount of treats should be <10% of the total caloric intake. Nutritional supplements are not required and, in fact, may be harmful. In an animal prone to obesity, the caloric content of all treats fed should be considered in an effort to match energy intake to expenditure. Regular assessment of the animal’s body condition helps ensure minimal weight gain beyond optimal adult values throughout life.
Most inactive, neutered adult cats can be fed a reduced fat diet (9% dry-matter basis) ad lib, but increasing the insoluble fiber content may be necessary in some animals to satisfy hunger. Cats exposed to variations in temperature (eg, cats that remain outdoors year-round or at night) may eat more during the winter. The need for a different nutritional profile in older cats versus middle-aged cats may be necessary. Middle-aged cats are at increased risk of developing obesity, whereas older cats often have a difficult time keeping weight on. The ability of older cats to digest protein and fat is often less than that of younger and middle-aged cats. Therefore, it is important to feed a diet with highly digestible protein and fat sources. The quantity of these nutrients in the diet may also have to be modified (usually increased) to compensate for impaired protein and fat digestion. However, depending on activity level, feeding a food with a different fat and fiber content (increased or decreased as needed) may be required to maintain optimal body weight and condition.
Growth, pregnancy, and lactation greatly increase nutrient demands over those of maintenance. Growth diets have increased nutrient density, digestibility, and bioavailability to provide nutrients necessary in a smaller volume of food. Supplementation of calcium, phosphorus, and vitamin D beyond amounts present in complete and balanced diets designed for growth and reproduction is rarely necessary and may be contraindicated.
Overfeeding during growth increases growth rate. This is not desirable, because it is incompatible with proper skeletal development and also contributes to obesity later in life. Feeding methods for growing puppies should be individualized for the puppy and owner. General recommendations are that puppies between weaning and 6 mo of age should be fed three times a day; puppies 6–12 mo old should be fed twice daily. Large- and giant-breed puppies should be fed complete and balanced growth diets that have been tested in feeding trials and that contain calcium, fat, and protein at levels closer to the minimums stated by AAFCO. Small-breed puppies may have to be fed more than three times a day using a tested diet that contains calcium, fat, and protein at levels greater than the minimums stated by AAFCO.
Only limited data have been published with respect to breed growth curves. Nonetheless, a slow growth rate is preferable to a fast growth rate. Weight gains should be closely monitored (weekly), and feeding recommendations adjusted such that the puppy gains a small amount of weight each week. When growing large-breed puppies were fed 50%–70% of their littermate’s ad lib intake, adult height, length, and bone or muscle mass were not stunted; only total body fat was affected. It is difficult to stunt the growth of a puppy being fed a complete and balanced growth diet that has passed an approved AAFCO feeding trial using meal feeding of an appropriate amount for 2–3 times/day.
Feeding recommendations for pregnant bitches through the first two-thirds of gestation are the same as those for maintenance. A common mistake is to overfeed during early gestation and to underfeed during lactation. In the last third of gestation, the total amount of food offered should be increased at least 20%–30% over the amount for maintenance. Growth diets are often used during gestation because of their higher energy density and smooth transition after parturition to support lactation.
Depending on litter size, lactating bitches often require energy levels 2–4 times those of maintenance to avoid excessive loss of body condition. Ad lib feeding using a complete and balanced growth diet containing 10%–20% fat (dry-matter basis) that has passed an approved AAFCO feeding trial is recommended to maintain lactation and to permit optimal body weight and condition to be required by weaning. If a bitch loses significant body condition during lactation, the fat content of the diet should be increased to 20%–30% fat (dry-matter basis), and she should be fed ad lib.
One of the most important differences between queens and bitches is that pregnant queens exhibit a linear increase in weight (fetal growth) throughout pregnancy. As a result, pregnant queens need to consume more calories almost immediately after becoming pregnant. In contrast, fetal growth is minimal during the first two thirds of the pregnancy in the bitch, and caloric intake does not generally have to be increased until sometime between the end of the second third and the beginning of the final third of the pregnancy.
Because queens tend to lose weight during lactation regardless of diet fed, it has been assumed that net tissue reserves should increase somewhat in preparation for lactation. A growth diet for kittens that contains 10%–35% fat, 30%–40% protein, and low (<5%) fiber (dry-matter basis) should be fed. Growing kittens and pregnant and lactating queens can be fed ad lib or several times a day to meet their daily needs. During the latter third of gestation, the amount of food and level of nutrient intake normally increases an average of 25%, although energy intakes for cats during pregnancy have been estimated to be as much as 40% greater than for maintenance. Some queens may eat less early in gestation and immediately before parturition; such changes are of concern only if prolonged. Queens require 2–3 times the normal food intake during lactation, depending on litter size. Supplementing an already balanced diet is not necessary and should be discouraged.
Older dogs and cats may not be as efficient in metabolizing dietary protein than younger animals.They may actually require more dietary protein than their younger counterparts to maintain protein reserves and maximize protein turnover rates. In addition, decreased fat digestion occurs with age in cats, so geriatric cats may actually require a higher-fat diet than their younger counterparts. In contrast, some dogs and cats begin old age considerably overweight, whereas others may show some loss of condition. Feeding an appropriate food with a different nutrient profile with respect to energy, fat, or fiber content (increased or decreased) may be needed to maintain optimal body weight and condition. Geriatric dogs and cats should be monitored in a preventive health program that includes periodic assessments of body weight and condition. The incidence of chronic degenerative organ disease increases with age, and early diagnosis fosters earlier treatment and more effective nutritional management.
The caloric needs of working or stressed dogs may exceed the levels of a maintenance diet, depending on the animal and extent of work performed. Most diets designed for work or stress have increased levels of animal fats, with the other nutrients appropriately balanced to the increased energy density. At extreme levels of stress (eg, an Alaskan sled dog requiring 10,000 kcal/day), many recommend not only increasing the percent ME from fat but also from protein, while minimizing the contribution of carbohydrate.
Any daily feeding recommendation should be considered an estimate or starting point and should be modified based on continual evaluation of the dog’s weight and condition, skin and coat, performance, and general attitude. Feeding a smaller amount of the daily ration (eg, ⅓ of the daily amount) before beginning a work shift is recommended with the remainder being fed thereafter. Plenty of fresh water should be available, and opportunities to stop work for a water break should be scheduled in any daily work routine for these dogs.