Over the past decades, the pet food industry has provided convenient and economical foods for domestic animals. Because the public has become comfortable with the idea that commercial pet foods can provide complete and balanced nutrition for the life of the animal, basic diet is no longer generally considered an important source of disease. Pet owners and veterinarians have literally been trained to look elsewhere for causes and treatment options. By ignoring the basic diet when advising pet owners, doctors and retailers are forgetting basic physiological principles: the importance of fresh and varied foods in the diet and biochemical individuality. What food consumer in their right mind would believe that food in a bag or can would provide all the nutrition they (personally) would ever need? This is the basis for most “alternative feeding philosophies.”
The Association of American Feed Control Officials (AAFCO) has published dietary recommendations for domestic species in the form of nutrient profiles. These nutrient profile recommendations are the result of expert evaluations of National Research Council (NRC) recommendations. The NRC recommendations were based on diets using purified nutrients, assuming 100 percent bioavailability. AAFCO, an organization composed of government, academic, and industry experts, evaluated these recommendations and initiated legislation requiring improved testing and labeling of pet foods (Dzanis, 1995). All pet foods must now conform either to AAFCO nutrient profiles or undergo AAFCO approved feeding trials before being marketed.
These improved procedures do not represent a perfect solution for nutrition of the individual animal, however. In the words of Quinton Rogers, DVM, PhD, one of the AAFCO panel experts, “although the AAFCO profiles are better than nothing, they provide false securities. I don't know of any studies showing their adequacies and inadequacies.” Rogers also states that some of the foods which pass AAFCO feeding trials are actually inadequate for long term nutrition, but there is no way of knowing which foods these are under present regulations (Smith, 1993).
An additional consideration in domestic animals is breed and function. For instance, the diets of broiler chickens have had to be revised over time as birds with higher body weight gain rates were developed (Morris, 1994). A recent study showed that different breeds of dogs exhibit different abilities to digest the same diet (Zentek, 1994). Working animals may perform better (and therefore require) diets high in protein and fat, rather than carbohydrates (Kronfeld, 1977); diets like these are not commercially available. Breeds of dogs that may have developed over hundreds of years as lap-sitters (like the Chihuahua) may well have different requirements than a less popular working breed such as the Anatolian Shepherd, depending on how their diet was related to their locale of origin, their function, and how long they have been bred as pet animals eating commercial diets.
Even if our domestic animals were of a homogeneous “race” like their ancestors, such as the wolf, panther, buffalo, or wild horse, individual differences in physiology and metabolic processes exist. Biochemical individuality, pioneered by Roger Williams, applies in many ways to domestic animals. Williams determined that even in normal humans (who are of relatively consistent size and shape), the needs for most nutrients vary over a fourfold range, on average (Williams, 1977). These factors will vary further according to age, activity level, existing disease and concurrent drug therapy. Recent advances in genetic research have led to a change in the way nutritional scientists view animal nutrition, a new paradigm, if you will. More and more conditions are viewed as nutrition-responsive.
According to a recent review by Eckhardt (2001), gene based diversity in nutritional requirements will be an area of focus for human nutrition now that the human genome has been sequenced. In particular, researchers must determine what levels of diversity exist, and what the practical implications are for nutritional individuality. To illustrate the point, 30–40 nutrients are recognized as essential. If the metabolic pathway influencing nutritional requirements for EACH of them was affected independently by just two alternative alleles at a single genetic locus (which is probably an oversimplification), then the number of alternative genotypes for that nutrient would be over 200 trillion! Eckhardt said, “.... some nutritionists already are working at the cutting edge of genetic research, in a conceptual framework that sees our expanding knowledge of human diversity as broadening the concept of normality rather than as documenting an expanded array of infirmities.” The new science of euphenics (“knowledge of individual nucleotide sequences can be used to optimize elements of each person’s lifestyle”) will impact veterinarians directly and force us to face every-day diet concerns in every animal as an individual, and adopt nutritional counseling as an everyday medical procedure.
It should be clear that, in addition to uncertainty about the more subtle animal requirements in general, individual animals vary so much in their metabolic function that a blanket recommendation for "any good commercial diet" may not address the individual pet's optimal health potential. In general, when we think about how to feed pets, we try to refer to the "Paleolithic" diet as a starting point. Carnivorous pet animals like the cat, (or facultative carnivores, like the dog) are presumed to need high quality meat, whole grain and high quality fiber sources, along with adequate fat levels, vitamins and minerals. Animals whose individual needs differ due to inbreeding or genetic abnormalities (perhaps common in purebreds) should receive individualized dietary consideration when problems of any sort occur. One extreme example is the Dalmatian. This breed has a tendency to form urate stones, and the prevention most commonly recommended is a vegetarian diet. Each breed, as well as each individual, represents a unique challenge.
The profession has historically recommended that owners NEVER feed real food (or table scraps) to pets. That position needs to be re-evaluated now. Some veterinarians now recommend supplementing the diet with meat and vegetables, for (facultative) carnivores such as dogs or obligate carnivores such as cats. This practice may provide the pet with phytochemicals and other vital nutrients that have yet to be recognized as essential by nutritional science. The National Cancer Institute has promoted their “five-a-day” program to encourage people to eat five to nine servings of fruits and vegetables a day—this is because studies examining individual nutrients, such as Vitamin A or E, simply haven’t prevented cancer as well as real fruits and vegetables in the diet—and we don’t know what is in real foods that works so well. Is it such a stretch to believe that we also don’t know everything about carnivore nutrition?
Diets espoused by popular authors are in widespread use by many pet owners. These range from diets formulated on nutrition formulation programs which theoretically provide complete and balanced recipes (Strombeck, 1998), (Pitcairn, 1995) to more extreme diets such as raw, grainless and BARF (Bones and Raw Food) diets.
Biochemical and mathematical analysis of the BARF and other raw diets has shown that there are significant imbalances in some minerals. Calcium, phosphorus, zinc, magnesium and iron were either low or high in these analyses. The diets were also cultured for enteropathogens, and E. coli 0157 was found in one of the three diets examined.
Unfortunately, devotion to the BARF and other philosophies for feeding pets has reached near religious levels in some groups. Many owners will not divulge this practice to their veterinarians because of fear about the doctor’s response. For this reason it is critical to ask owners about what diet they are using, and try not to be shocked or judgmental if they are feeding according to one of these plans. Note the animal’s condition well, inform the owner that the diet does not fit classical “complete and balanced guidelines,” and ask them to come in for check ups at six-month intervals to monitor the effects of this new diet. Many owners, proud of their discovery, may willingly follow these directions if they believe they are partners in diet research.
Special Considerations for Cats
Some alternative feeding philosophies teach that dry food is bad for cats, for a number of reasons. First, dry food encourages free choice feeding, which may lead to obesity and addiction in many cats. While cats are thought to naturally eat many small meals per day, these meals would not (in feral cats) consist primarily of grain, but of protein loaded bugs, lizards, rodents and birds. There is increasing suspicion that free choice dry feeding may complicate diabetes in cats, and some holistic practitioners wonder whether this practice may even predispose to diabetes. Finally, cats with chronic crystalluria or a history of stones should be managed by diluting the urine; this is naturally and more easily accomplished using canned or homemade food, rather than dry food.
Breed and individual genetic differences may be one reason why certain pet animals seem to require individualization of the basic diet. Formulas made by major manufacturers keep the majority of pet animals healthy and well, but for animals with problems, the nutritionally minded veterinarian will change diets and often discover very basic disease mechanism easily remedied with food therapy. Holistic practitioners use a variety of commercial diets especially Innova, California Natural, Pinnacle, Flint River, Wysong, NutroMax, Best in Show, Canidae/Felidae, Precise and Azmira; and sometimes those by the major manufacturers such as Hills, Iams, Purina and Waltham. If owners are interested in preparing homemade foods, there are a large number of choices available. A combination of commercial diet plus fresh meats and vegetables (50:50) may provide some assurance of safety AND the advantages of freshness and variety. As veterinarians, we are obliged to listen to these owners’ concerns and help them find the best choice for their pet.
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