This article exclusively written for Carnivora™ by Brenda Hagel

The key to healthy nutrition for people is variety and moderation. When it comes to diet, there’s no "one size fits all" approach that’s right. For pets eating dry and canned foods, it’s been a different matter completely. Pet food manufacturers claim that given a complete, balanced diet appropriate to the age and physiological state of the animal, that diet should be fed and nothing else. Just like people, dogs and cats also need variety in their diet for a number of reasons. In order to understand why variety is so important, you have to first be aware that many nutritional inadequacies have appeared with "complete and balanced" commercial pet foods.


The Myth of "Complete and Balanced" Pet Foods

The Association of American Feed Control Officials (AAFCO) dictates whether a pet food is "complete and balanced." They regulate the amounts of fat, carbohydrate, protein, trace minerals and vitamins that go into pet foods. Any pet food company can produce a diet that meets AAFCO’s standards, yet pets can become malnourished on that diet. Why? The reasons are many.

AAFCO standards are based on only "minimums" and a few "maximums," not "optimums." Minimum levels do not address a pet’s individual nutrient requirements to stay well much less manage any illnesses that may develop it ages. "Complete and balanced" pet foods have been known to be deficient in certain nutrients, which is why even AAFCO recommends rotating foods periodically. The fact that pet food nutrition is a dynamic field can be exemplified with a problem that at one time afflicted thousands of pets eating commercially produced pet foods. Although the foods had apparently been "complete and balanced", they were actually deficient in the amino acid taurine. A lack of taurine in cat diets results in Dilated Cardiomyopathy (heart muscle disease). Besides DCM, deficiency symptoms of taurine include poor reproduction and central retinal degeneration (CRD). Cat foods are now supplemented with taurine. New research is suggesting that taurine supplementation may also be beneficial for dogs, but as yet few manufacturers add extra taurine to dog food. Inadequate potassium in certain feline diets also caused kidney failure in young cats; potassium is now added in greater amounts to all cat foods.

On the other hand, a pet food that contains an excess of certain nutrients, can lead to toxicity if the same food is eaten over a long period of time and the pet’s body cannot excrete excesses. For instance, one pet food company claims that because thiamine (B1) is readily destroyed by heat, excess levels are added to their pet food in order to contain the correct amount after processing and ensure levels meet with AAFCO recommendations. However, supposing they add too much? Long-term excessive use of thiamine can produce symptoms of hyperthyroidism. One particular study (University of Georgia) demonstrated that certain nutrients, such as magnesium, iron and manganese, were present in most dry dog foods at 200-400% more than biologically necessary. The Animal Protection Institute sampled commercial cat foods and found that over 75% of them contained more magnesium than was stated on the label. Excessive iodine levels, found in canned cat foods, have resulted in some veterinarians questioning its role in feline hyperthyroidism.

Pet foods seldom address individual requirements

"Complete and balanced" pet foods are designed to be adequate for the "average" dog or cat but do not address an individual animal's unique and variable needs. Dogs and cats require different levels of nutrients due to various disease conditions or injury as well as any known nutrient losses through the skin, urine and the intestinal tract. The interactions of medications may affect absorption of nutrients. In addition, environmental conditions must also be considered.

Vitamin-mineral mixtures are added to pet foods. Vitamin and minerals are associated with different absorptive capacities. The absorption of these nutrients depends on a number of physiological, biochemical, and hormonal characteristics of the dog or cat and the form of the vitamin or mineral consumed. Sources used in pet foods are not all alike and may not be evaluated for bioavailability.

Factors that enhance vitamin and mineral absorption include the form of the mineral ingested, maintenance of chemical stability, presence of a specific transporter, particle size, solubility, and intestinal motility. Factors that inhibit absorption include oxalic acid in certain vegetables, phytic acid in certain grains, fiber, sodium, tannins, protein, fat, rapid transit time, malabsorption syndromes, other vitamins and minerals, hormones and nutritional status. All of these factors make it difficult to define the exact optimal nutrient requirements for an individual animal.

Variety in evolutionary nutrition

If you don’t feed "complete and balanced" pet food, how do you feed a dog or cat a "balanced" diet? By feeding a variety of foods over a period of time! While not every meal meets the animal’s nutritional requirements, the diet as a whole does. This is the way all wild species have eaten for eons and the way pets ate before the advent of "complete and balanced" pet food.

Early feeding experiences incorporating a variety of tastes and textures generally result in dogs and cats that prefer a variety of foods. In an evolutionary sense, it is advantageous to prefer variety in the diet in order to increase the probability of expanding the range of available food sources and the nutrients they offer. In nature, variety also reduces the chances of providing excesses or deficiencies of particular nutrients consumed day after day.

When a wild carnivore feeds, each meal is likely to be different in content. One meal may be totally vegetarian consisting of fruits. A meal may consist of a whole prey animal while another may consist mainly of internal organs. One meal may be lower in fat while the next may be higher in fat. The type of fats would also vary. Some meals may supply mostly minerals from bones, while some, only pure meat.

For more than fifty years, scientists have known that animals have the ability to sense when their diet is not providing sufficient amino acids. Of the 20 amino acids found in dogs and cats, ten of them cannot be produced by or stored in the body and, therefore, must be obtained through the foods the animals eat. These ten are known as "indispensable amino acids." Research has shown that animals can sense within a matter of minutes if their diet is deficient in an indispensable amino acid, making use of a subconscious sensing mechanism that does not depend on taste or smell. For example, if an animal is offered a food that is deficient in an indispensable amino acid, they will soon switch to another that provides the necessary amino acids.

Variety and moderation helps eliminate sensitivities to foods in allergy-prone individuals

Heredity is often cited as a cause of food allergies, and it certainly plays a role since a recessive gene has been identified as being linked to IgE-mediated food allergies. Repeated exposure to the same foods, especially in large quantities is also a factor. This is why it is important that you rotate and vary the diets or foods you feed your pet. Eating foods on a rotated basis reduces their exposure to them and hopefully will help preserve their tolerance for them. Continuing to bombard the body with the same food risks turning on the food-antibody response. Rotation of diets makes good sense for every pet, and especially for those with food allergies.  Variety may allow pets to eat foods that they have a mild or borderline allergy and which they might not tolerate if consumed often.

Variety maintains enthusiasm for meals and encourages a healthy appetite

Well, this is simple. Imagine eating dry boxed cereal, without milk, for your entire life. Could you do it? Not likely! Not only would you crave the taste of other foods, but also, commonsense would tell you something was missing in your diet! No fresh vegetables or fruit, no meat and none of those scrumptious snacks you've come to love. It wouldn't take long before most people would be desperately searching for a salad, a barbecued steak or anything that was different! Researchers say that dogs and cats are not as emotional about food as people are. Maybe that just applies to laboratory animals, since pet owners that feed a variety of foods to their pets would disagree.

Vegetable Variety

Fruits and vegetables are clearly an important part of a good diet for people. For those that also follow this nutritional approach when feeding their pet, the same rule of thumb applies: no single fruit or vegetable provides all of the nutrients needed to be healthy. The key lies in the various vitamins, minerals and phytonutrients in different fruits and vegetables. Although all fruits and vegetables contribute beneficial nutrients, green leafy vegetables such as lettuce, spinach, Swiss chard, and mustard greens; cruciferous vegetables such as broccoli, cauliflower, cabbage, Brussels sprouts, bok choy, and kale; and citrus fruits such as oranges, lemons, limes, and grapefruit (and their juices) make important contributions.

Meat Variety

Just as with vegetables and fruit, no single source of meat will provide all of the critical nutrients common to its food group. The meat from different species has a unique biochemical makeup and amino acid structure. Feeding pets a wide variety of meat, bones and organs from sources such as beef, chicken or lamb, provides a broad base of amino acids and nutritional components such as fats, essential fatty acids, vitamins and minerals.

Meat is classified as a source of high quality biological protein. Protein quality is measured by the ability of a food to provide a balanced pattern of essential amino acids. The dog and cat have a physiological requirement for 22 different amino acids, which are the building blocks for protein. Only 10 of the 22 amino acids are essential amino acids that must be supplied in the diet. On a muscle tissue (meat only) basis the amino acid profile between livestock species varies little. However on a whole meat basis (bone, fat and connective tissue included), the amount of amino acids can be affected considerably. Young animals show higher values than old ones in most of the amino acids.

The meat within a species differs in composition according to the degree of fatness, age and sex. The amount of connective tissue in a meat cut also provides a different spectrum of amino acids due to the collagen and actin. Livestock animals supply various ranges of nutrients depending on what they have been fed and the time of year they are slaughtered. Winter feed may not provide the same nutrient levels to livestock that summer feed can provide. Meat animals may be lower in certain nutrients due to low levels of nutrients in the soil and will vary from one region to another.

Feeding pets a variety of meat sources provides a broad base of amino acids and nutritional components such as fats, essential fatty acids, vitamins and minerals. For instance, beef is an average source of niacin, riboflavin, thiamine and vitamin B6, but it is an excellent source of zinc and iron. Pork is an excellent source of thiamine, a good source of niacin and only an average source of riboflavin and vitamin B6. Beef and lamb are excellent sources of iron and have higher iron content than pork, chicken or fish. Beef and goat supply more zinc than does lamb, pork and chicken.

Fat Variety

All fats are composed of fatty acids, of which there are dozens in nature. Generally, the more saturated the fatty acid content, the harder the fat will be at room temperature; the more unsaturated its content, the runnier it will be. All fats are a mixture of different fatty acids.

The fat surrounding and within meat and organs contains a number of fatty acids. For instance, beef fat is about 51% monounsaturated fat, 45% saturated fat and 4% polyunsaturated fat. In addition, one-third of the saturated fat in beef is stearic acid. Conjugated linoleic acid (CLA) is a naturally occurring fatty acid derivative of linoleic acid that is found predominately in grass fed beef, but not in useful amounts in poultry. Grass fed meat also has a higher ratio of omega 3 fatty acids than grain-fed meat animals.

Chicken fat is about 31% saturated, 49% monounsaturated (including moderate amounts of antimicrobial palmitoleic acid) and 20% polyunsaturated, most of which is omega-6 linoleic acid, although the amount of omega-3 can be raised by feeding chickens flax or fish meal or allowing them to range free and eat insects.

Duck and Goose fat are semisolid at room temperature, containing about 35% saturated fat, 52% monounsaturated fat (including small amounts of antimicrobial palmitoleic acid) and about 13% polyunsaturated fat.

Pork fat is about 40% saturated, 48% monounsaturated (including small amounts of antimicrobial palmitoleic acid) and 12% polyunsaturated. Like the fat of birds, the amount of omega-6 and omega-3 fatty acids will vary in pork fat varies according to what has been fed to the pigs.

Rather than striving to achieve complete nutrition for your pet per meal, consider that the basic premise of any good diet is variety, balance and moderation over a period of time. After all, this is the way we provide good nutrition for ourselves. It should be no different for our dogs and cats.

Copyright© Brenda Hagel


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