Animal nutrition developed as a production science. The goals of early nutrition research were to optimize productivity, and food intake often was assumed to be maximal. Although appropriate for production research, such intakes are not always appropriate. In particular, a goal of veterinary clinical nutrition is to maximize quality of life and longevity. These goals often necessitate restriction of food intake. The effect of food intake on companion animal nutrient intake and health is thus an important veterinary clinical nutritional issue.

The role of food intake in our patients depends on what food and treats the owner offers, and how much the pet consumes. To obtain an accurate diet history, try to interview the person who feeds the animal, avoiding leading questions to the extent possible. The goal is to identify the presence and significance of factors that would put the patient at risk for malnutrition.

The depth of the assessment may be cursory, intermediate or detailed depending on the presentation, as shown in the table below.

Healthy pets

If the pet is in normal body and muscle mass condition, the owner is feeding a satisfactory diet, and food intake seems reasonable, one usually does not need to investigate further. If the animal is in a higher risk group, for example if it is gestating, lactating, growing, geriatric, living in a multi-pet household or is an endurance athlete, and the physical examination is normal, an intermediate evaluation may be useful. This would add assurance of the quality and availability (especially in multiple pet households) of the diet, and estimating food intake to calculate protein intake in addition to the cursory evaluation. One can estimate the quality of the diet by identifying that a reputable manufacturer makes it, and that the food has passed feeding tests for all stages of the animal's life. The pet's access to the food can be assessed by the ability of the owner to measure the intake of the animal in question. One can get a quick idea of the adequacy of intake by determining protein intake. Determine protein intake by multiplying the pet's food intake by the % dietary protein on the food label and compare the result with the animal's needs as shown below.

 Grams of Protein Intake= food intake in grams x % dietary protein in food from the label.

 Protein Need= Minimum protein requirement for species x lean body mass (kg.)

 Recommended minimum protein intake:

 Dogs--2 grams protein for every 1 kg. lean body weight

 Cats--3 grams of protein for every 1 kg. lean body weight.

 Intake (gm) + kg BW should be > recommended minimum

Detailed evaluation of the diet is indicated when the animal is in a higher risk group, and any abnormality is identified on the physical. Detailed evaluation includes all of the above, plus further investigation of the pet's nutrition-related features of the environment as appropriate.

Food intake should be determined at all stages of life. For example, owners should be asked to measure the usual food intake of pregnant females at the time of breeding at this time; it will be important to remind them of this information when the offspring are weaned. After weaning, the mother is returned to the diet she was consuming prior to breeding at half the amount the owners measured at the time of breeding, increasing her food intake to her usual amount over next two to three days. This amount often is much less that she was previously eating, which may concern the owners if the reason for the restriction is not explained.

Proper feeding management also is usually much more important than diet choice in young growing animals, because most problems are caused by overfeeding.

Experimental studies of nutrition and developmental orthopedic diseases (DOD) in dogs agree that restricting intake so that the pup maintains a lean body condition during the period of growth is the best insurance against nutrition-related problems. Owners need to be taught how to recognize the desired body condition and reminded not to trust feeding recommendations on food containers, as they may not be accurate for their dog in their environment.

Young growing animals should be maintained in a lean body condition. This means that the ribs should be easily felt, and barely seen in smooth coated dogs. Feeding to this condition will minimize the risk of orthopedic problems and still permit the animal to reach its genetic potential for adult size. The dog should be fed however much food is necessary to maintain this body condition, and the range is large. Some dogs can have food available continuously, whereas others may need to be restricted to brief access to food once or twice a day. If the owner understands this from the start, it's much easier for them to adjust the amount of food they offer their pet. Recommendations on dog food labels can be used as an initial estimate, but should not be used as a substitute for the "eye of the master" to adjust intake as the animal grows. Feeding to a body condition rather than a number of cups or cans of food in a bowl is the best insurance against orthopedic problems in growing dogs; however, clients should be advised that genetic peculiarities and trauma also can cause DOD, and that these problems cannot be prevented by diet.

Healthy adult dogs have relatively small nutrient requirements compared with the productive stages of life. They may maintain themselves for years on a wide range of commercial or home-made diets with apparently little consequence. This adaptability may be an explanation for the fervent beliefs of some owners that a seemingly peculiar diet is so beneficial for their pet. The probability of a diet-related problem, however, should be lower for animals fed properly formulated commercial diets. This is because these diets have been thoroughly tested and fed to millions of animals successfully for generations. Because no adverse consequences were observed in a single animal does not mean that the diet provides superior nutrition.

Adults may be fed free choice, where food is available at all times, or they may be fed by hand, with the owner determining the size of each meal. Self-feeding is more convenient, and in group-feeding situations ensures that timid animals are not denied access to food. It has the disadvantage of reducing owner contact with the pet, and decreasing opportunities to evaluate the animal's body condition and general health. Pets that tend to overeat should be fed by hand once or twice daily in amounts sufficient to maintain moderate body condition.

For working dogs during training, the amount fed daily should be sufficient to keep the dog in the desired body condition. If the work is really hard, the dog should be lean (BCS 2/5). The amount of food needed should not be overestimated. For example, greyhounds that race only once or twice a week and do little other work may require only about a 25 percent increase in food intake.

Hunting dogs in hard training may require two or three times their usual food intake, about the same increase required by bitches nursing large litters at peak lactation. It has been reported that racing sled dog teams may require as much as 4.5 fold increases in nutrient intake to sustain them during races. These extremes emphasize the need for the trainer to determine the needs of hard working dogs by daily evaluation of body weight, condition, and performance.

Food intake also is important for geriatric pets. Older patients should not be ad libitum fed. Although this method may be adequate for younger animals, the importance of maintaining normal body condition, and regular observation of the animal's food intake, make once or twice-daily hand feeding advisable for older pets. Because of the increased incidence of disease in older pets, clients should be advised that sudden unexplained decreases in food intake could be an early sign of disease that should be investigated. Obese dogs may be fed small quantities of food 3 or 4 times each day to reduce begging.

Sick Patients

Diet therapy for nutrient-sensitive diseases usually includes restriction of intake of one or more nutrients. Because many (most?) patients with such diseases are older and don't eat much, the risk of inadequate intake of nutrients must be assessed. This is particularly true when the therapy is anticipated to continue for months or years. To avoid iatrogenic induction of nutrient deficiencies, one must compare the number of grams of nutrient in the amount of food consumed with the needs of the patient. For example, the minimum dietary protein intake to sustain protein reserves in cats is approximately 2 grams per pound per day. If a cat consumes 20 kcal per pound body weight per day, the diet would need to contain at least 10 grams per 100 kcal to provide enough protein to meet the cat's needs. If the cat consumed 30 kcal per pound body weight per day, only 6.7 grams protein per 100 kcal diet would be necessary.

Many veterinary foods intentionally contain restricted amounts of some nutrients. For these reasons, estimates of daily minimum intakes of some essential nutrients (amount per pound body weight) for adult, average sized pets are presented below:

General feeding suggestions

I recommend that veterinary foods be introduced to patients gradually. This strategy is intended to avoid creating a learned aversion, which is the pairing of the novel diet with the ill feelings associated with the disease. Offering therapeutic diets to patients when they were ill may be the reason many patients reject them, which has led to their reputation for poor palatability. I prefer to send patients home to be fed their usual diet until they feel better. During this period I try to encourage the client to measure the patient's food intake, so I can estimate nutrient intake. The smaller the amount consumed, the higher the nutrient concentration of the therapeutic diet must be to avoid the risk of deficiency. Once the patient's usual food intake has been determined, a veterinary food with appropriate nutrient density to avoid the risk of any deficiencies may be chosen, and the new diet can be introduced. I suggest offering the new diet as an alternative to the usual food initially, rather than prohibiting intake of any of the usual food by removing it completely. As the new diet becomes familiar to the patient, the amount of the usual diet provided may be reduced and eventually replaced over a couple of weeks or so. Remember, it is always better for a patient to eat some of the "wrong" diet than none of the "right" diet!

If, after a period of acceptance of the therapeutic diet, the patient refuses to eat it, the owner should be asked if the patient would still eat the usual diet or favorite foods. If so, I suspect distaste for the diet. If the animal is inappetant toward all foods, I suspect exacerbation of the disease, and recommend return to the hospital for re-evaluation.

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