A Human Need- Dogs and Cats
Ten thousand years ago human beings began domesticating dogs and cats. People were interested in using these animals for service, such as herding livestock, hunting game, and vermin control. Today pets’ primary role is for companionship and pleasure, with few doing any work. Most people relate to animals, and some develop relationships that are more important than for humans. People realize the importance of maintaining a pet’s health to insure a long and satisfying life. This website is about feeding pets to support a long and healthy life. How a pet is fed determines its health and life expectancy more than other care. Advertisements for pet foods state that; they headline their products with "You are what you eat."
Feeding Pets to Insure a Long and Healthy Life
Adequate and balanced nutrition is necessary for all life’s well-being. Inadequate nutrition produces many disease conditions and can shorten life expectancy. This website describes new aspects of nutrition and dietetics for maintaining the health of dogs and cats. Nutrition is the sum of the processes involved in the consumption, assimilation, and conversion to energy of food nutrients. These processes provide the foundation for life and health. Dietetics is the management of diet and the use of food, the science concerned with the nutritional planning and preparation of foods. Why is this information important?
Most of the world's companion animals depend on humans to supply their nutritional needs. In their native state, cats and dogs apparently selected nutritionally complete and balanced diets, but with domestication generally a single food is presented, which eliminates the choice animals previously exercised.1
The provision of single foods such as commercial pet foods also eliminates the choice humans can make for their pets. The pet food industry claims that pet owners should feed a commercial pet food in order to feed a nutritionally complete and balanced diet. Such diets are necessary to support normal growth of maturing animals and sustain nutritional needs of adult animals. Pet foods are generally adequate in supplying an animal's nutritional needs, but they are not always nutritionally complete and balanced.1 Formulating a balanced and complete commercial pet food can be difficult because many nutritional requirements of dogs and cats are merely estimates. Thus problems sometimes develop because of nutrient deficiency or excess in commercially prepared diets. This concern has been voiced to the pet food industry.
Pets are breaking down from disease at an unprecedented rate from a variety of problems. Why are so many pets getting cancers, renal failures, hepatic diseases, multitudes of skin and coat problems? Diseases and illnesses we simply shouldn’t be seeing. Illness and poor nutrition affect each other.
With relatively large numbers of pets getting sicker and sicker, we should take a serious look at what we’ve been providing for them. Food is clearly not the only determinant of health, but it is one of the only health-related factors pet owners can control.2
Surprisingly "most of our prehistoric ancestors had better diets and health than we do."3 Early humans foraged for food just like dogs and cats in earlier times. When foraging stopped, humans developed dramatic changes in one of few things that science can look at today, their skeletal structure. The changes were not due to evolution but to changes in diets and lifestyle. These changes put humanity on a path toward poorer, not better diets. For many, the poorer diets were based on eating corn. No longer foraging and eating more "perfect" diets, the foragers-become-farmers showed degenerative diseases not found in their foraging ancestors. The foragers were much more healthy and "almost totally free of internal parasitic infections."3 The conclusion is that "degenerative changes seen with aging develop after by a lifetime of neglect, in particular, eating improper foods and getting little exercise."3
Diets prepared for our pets today are very different from diets of a foraging animal. Current diets are based on cereals, similar to humans' diets when they stopped foraging. These diets are nutritionally adequate in being complete and balanced but do not insure maximum life expectancy. A number of canine and feline medical problems relate importantly to such diets. These problems are discussed throughout this website.
Americans are knowledgeable about nutrition and dietetics because they plan and prepare most of their meals. Owners rarely plan and prepare meals for their pets, however. They leave that to the pet food industry. This industry claims to produce safe and nutritionally adequate diets and that pet owners are not competent to do this themselves. They are told that only nutritional experts should formulate a pet's diet. Pet owners should be concerned that a diet is more than nutritionally adequate and is more than complete and balanced, however. Owners want to feed a diet that insures maximum life expectancy. Such a diet is never responsible for causing disease. Diets are a reason for animal diseases, however. Ideal diets maintain harmony between owners and their pets. A pet's diet can influence unwanted behavior such as destructive chewing or ingesting matter like plants, stones, or feces. The diet can also affect behavior patterns of defecation and urination. Inability to control such behavior often leads to a pet’s euthanasia or abandonment. Unacceptable behavior destroys a pet’s value as a family member. Diet can directly influence aesthetic factors impacting a pet’s value. Diet is the primary determinant of digestive tract problems such as vomiting, diarrhea, voluminous or odiferous feces, and flatulence. Pet owners often destroy or abandon pets with these problems. Owners can manage and often cure these problems, however.
Nutritional Education of Pet Owners
Veterinarians should educate people on feeding pets. Counseling owners on feeding is the most important client education a veterinarian can offer. This education must be more than to advise feeding a commercial pet food. A pet can be fed foods consumed by human beings. Client education begins with instruction on feeding puppies and kittens which establishes a pattern for lifelong pet care, an important practice of preventive health. Education on feeding is to promote wellness and identify risks for preventable medical problems. A good knowledge of feeding can prevent many medical problems.
Teaching hospitals at veterinary schools could do more client education on care and feeding of newly acquired pets. Owners usually ask simple questions. What type of pet food is best to feed? What food do you recommend? How much and how often do I feed? How can I feed to insure maximum growth? What can I feed so my pet will have a beautiful coat? How should I feed my aging dog or cat? Students and clinicians usually answer these questions from their anecdotal experiences, and recommendations are seldom consistent. Little pet care information is volunteered if clients ask no questions. Veterinary students usually learn about pet nutrition during their first or second year. Unfortunately, little is done to promote any application of this knowledge during their clinical training. If students fail to use that information they soon have no knowledge or appreciation of nutrition for the dog and cat; it is lost.
Sources of Knowledge on Nutrition
Veterinarians often provide little nutritional education because the pet food industry has "taken this off their hands."4 The industry prints and distributes feeding information for veterinarians to give clients. Pet food companies use such information to promote sales. The industry’s nutritional experts educate veterinarians and veterinary students to use their products. Some companies give their products, at no cost, to veterinary students. Pet food companies also sponsor seminars for veterinarians, with the goal of selling more product. This hasn’t improved veterinarians’ knowledge of nutrition. A survey of veterinarians reported that nutrition training is inadequate in veterinary schools and quality of nutrition continuing education is inferior.5
Pet owners are interested in nutrition and dietetics which is expressed very well in a book written to provide the practicing veterinarian with up-to-date information on canine nutrition and feeding management, one that would be useful for veterinarian, pet owner, and their dogs:
One need only read the health sections of major newspapers and weekly news magazines to gauge the level of public interest in nutrition. A number of subjects have been scrutinized: food additives, preservatives, known or suspected carcinogens, dietary cholesterol and its effect on cardiovascular disease, megavitamin therapy, and dietary influence on tumor behavior to name but a few. Coupled with the public interest is a major movement away from highly processed foods back to "natural" or basic "organic" food sources.
Some argue that the focus of attention has turned toward nutrition as a direct result of the social concerns raised over the ever-expanding world population and the projected inadequacy of food supply and delivery systems. Others see it in part as a personalization of the environmental movement. The heightened awareness of the importance of nutrition is probably also influenced by the success of modern medicine in eliminating many of the diseases which at one time were the major causes of death in the population.
Regardless of the reasons, concern about nutrition has reached an all-time high. Many people are vitally concerned about the quality of their diet and its effect on their personal and family health. It stands to reason, then, that the pet-owning public will transfer these concerns to the nutrition of their pets as well.
Over the past decade, our knowledge of canine nutrition has grown steadily. Sadly, however, only a variable amount of this information has reached the practicing veterinarian whose knowledge of canine nutrition is often not much more advanced that it was decades ago. Today we know much more about the varying dietary needs at different stages in a dog's life; about different needs for different diseases; about the relationship between diet and a dog's ability to deal with stress.
Questions from clients about nutrition at one time were simple. What kind of dog food is best? What food do you recommend? How much and how often do I feed? These questions were easily handled and required very little sophisticated knowledge of nutrition. However, as clients become more involved with their own nutrition, questions posed to veterinary practitioners become more complicated.
This changing awareness and interest affords us all a tremendous opportunity to improve client relations. Clients are seldom aware of the extent of our knowledge and skills. Very often they bring us their ill and injured pets and take them home well or healing. Many clients, however, never realize the many complicated steps that occur between admission and discharge. Much of their impression of the profession is based upon how we answer their questions. Nutritional guidance, then is not a subject to be taken lightly. We now have the opportunity to show our clients a part of the knowledge required to be a veterinary professional. Equally important at this "teaching moment" is the chance to guide dog owners on improving the health of their animals.6
Regardless of the reasons, concern about nutrition has reached an all-time high. Many people are vitally concerned about the quality of their diet and its effect on their personal and family health. It stands to reason, then, that the pet-owning public will transfer these concerns to the nutrition of their pets as well.
This website is written to provide nutritional guidance that is not found elsewhere. That includes nutrition counseling for use during client-patient visits to veterinarians. Unfortunately, many clients have been educated to believe that for most medical problems diet has nothing to do with recovering health; cures are found only in drugs or surgery.
Faulty Diets and
Inadequate nutrition in pets can be explained two ways. Faulty diet was an acceptable explanation in the past. With the feeding of commercial pet foods, that explanation is seldom acceptable today. Most people believe: With the variety of dog foods available to dog owners today, poor feeding management rather than faulty diet, is frequently responsible for many nutritional problems dogs experience."7 This means that for animals inadequately nourished, finding the proper diet solves the problem. Besides age and body size, an animal's activity is most important in deciding these requirements. The pet food industry claims animals gain optimum nutrition and health after feeding the correct commercial pet food. Therefore, feeding mismanagement is failure to select the right diet. What is the responsibility of the veterinarian in charge of advising a client? "More often it means providing the dog owner with a simple framework to aid in grasping the basics of canine nutrition."5 That means to provide an aid for selecting the correct commercial diet. But any diet, including commercial diets, can be faulty so that inadequate nutrition results not only from faulty management. A purpose of this website is to instruct veterinarians and clients on preparing complete and balanced diets for both healthy and sick pets. The pet food industry discourages owners from preparing a pet's diet. It proclaims:
Most people who have a cat or a dog do not have the degree of nutritional expertise, access to the appropriate raw materials, the time or the desire to pursue complicated preparation and cooking of food for their pets. As a consequence the manufacture of foods specially prepared for cats and dogs has developed, particularly over the last forty years, into what is now a large and sophisticated industry.8
Homemade diets are now rarely fed to dogs because of the availability of good, economical proprietary foods. However, some owners still elect to feed table scraps or to manufacture their own diets. These diets are rarely consistent from day to day and may vary considerably in their protein, carbohydrate, fat and vitamin content. Foods such as potatoes, cereals, and bread, if fed in large amounts, often precipitate diarrhea. (Cereals are the main ingredient in most dog foods, ed. note) Overcooking food will reduce its digestibility and lead to dietary diarrhea, while dogs maintained on fresh meats diets often have foul smelling fluid diarrhea. In all cases establishing a normal dietary routine will relieve the signs. This may have to be carried out in a hospitalized environment as owners often feel their dog will not eat commercial diets.9
Veterinarians are educated to believe that owner-prepared diets are likely to be faulty and cause medical problems. Human beings have nutritional expertise to prepare their own diets; that same expertise can be used to feed their pets. Human beings develop nutritional problems mostly from consuming processed foods and diets rather than ones they prepare themselves. Pet owners control dietary quality and wholesomeness when they prepare an animal’s diet themselves. Control is maintained over nutritional adequacy.
Balancing a Diet
Pet owners are advised to select foods labeled "balanced" or "complete;" such diets insure a long and healthy life. What does it mean to label a diet balanced? "A balanced diet contains optimal proportions of nutrients so that they can be utilized with maximal efficiency for a specific purpose." No one knows how to precisely formulate a diet with optimal amounts of nutrients, however. Amount of any nutrient falls in an optimal range than being a specific amount. Variable individual needs under varying conditions decide a range's breadth. Errors and imprecision in nutritional methods also decide the breadth. The optimal range is broader for maintenance of an adult animal living under conditions demanding small energy consumption. The range is narrower for animals with greater needs such as during growth, breeding, and hard work or stress.
Feeding a diet deficient in one or more nutrients affects performance and ability to gain weight. Inadequacies also affect number of offspring and ability to function or withstand stress. Feeding a marginally adequate diet may result in no signs during minimal demands on an animal. But when stress increases needs, that diet is nutritionally inadequate. In the optimal range increased amounts of nutrients do not affect performance. For example, greatly increasing thiamin does not affect a puppy's growth; it metabolizes excess thiamin. Minimum optimal levels for nutrients often changes for different physiological functions, such as physical activity, pregnancy, lactation, and growth.
Excess of any nutrient can be harmful. Nutrients as any chemical are toxic at certain levels. Some nutrients have a narrow range between adequacy and toxicity. Such nutrients are more likely to cause toxicity because of the way a diet is formulated or an animal is fed. Variation is also found for an animal’s ability to metabolize or excrete nutrients. With such ability limited, a nutrient can become toxic because its excretion lags behind intake.
The pet food industry does not measure some important nutrients in their products. Manufacturers admit to adding excesses for some nutrients to insure adequate levels in a product. Loss of nutrients, particularly of vitamins, is limited because baking or extrusion temperatures or time and sufficient supplements are added to counterbalance processing and storage losses.8 Supplementation to remedy this estimate of loss often results in some nutrients being in excess.
Requirements for a Diet to be Balanced and Complete
Pet Food Standards
What can be known about commercial pet foods that are complete or balanced? Pet food labels state whether nutrients are provided at levels required to be adequate for all life stages of an animal. This claim allows the label to describe the food as complete, perfect, scientific or balanced. How is a diet produced so it can be labeled as balanced or complete? Manufacturers can make this claim when they formulate diets following recommendations established by the Committee of Animal Nutrition of the National Research Council (NRC) of the National Academy of Science. The Council selects a committee to evaluate nutritional requirements and set standards for pet foods to meet these requirements. That committee is the authority on estimating nutrient requirements for all life stages of a dog or cat. For many years the NRC has been the only group to establish the standards for feeding dogs, cats, and other animals; all references to a diet being complete and balanced were based on the NRC standards. The pet food industry is now discarding all reference to the NRC and is establishing its own standards.
Industry Abandons NRC "Gold Standard"
The pet food industry created a group called the American Association of Feed Control Officials (AAFCO) which can either adopt NRC standards or establish its own, depending on wishes of the Industry. In 1974 AAFCO adopted NRC recommendations for using feeding trials to evaluate adequacy for pet foods. Such testing was too restrictive for some sections of the Industry, however. Thus, AAFCO designed an alternate procedure for claiming nutritional adequacy for a pet food. Instead of feeding a food to evaluate its adequacy, chemical analysis was done to decide if it would meet or exceed NRC requirements. Chemical analysis is unable to say anything about palatability, digestibility, and biological availability of nutrients, however. Chemical analysis’ lack of information on digestibility and biological availability does not tell whether a pet food can provide an animal's nutrient needs. AAFCO was aware of the limitations of chemical analyses and “solved” the problem by adding “fudge” or “safety” factors which established AAFCO’s own requirements for exceeding the minimum.1 The nutritional requirement with the added safety factor is a nutritional allowance.
The pet food industry abandoned the NRC's oversight following NRC's 1985 revision of Nutrient Requirements of Dogs. NRC challenged and upset the Industry by the revision's statement "Users are advised to obtain evidence of nutritional adequacy by direct feeding to dogs." On discarding the NRC standards AAFCO established itself as the authority for Industry to follow; Industry established its own standards. With AAFCO establishing the “gold standard,” pet food manufacturers no longer must follow NRC standards for formulating a pet food. Anyone can produce pet food merely by following AAFCO’s formulas.
In the 1985 NRC revised Nutritional Requirements of Dogs nutritionists renewed the call for feeding trials to determine whether pet foods are complete and balanced. Feeding trials must be done to show that animals fed a pet food remain healthy and grow or maintain body weight, depending on their age and stage of life. What is the effect of this NRC position? It challenges the pet food industry; 'Users are advised to obtain evidence of nutritional adequacy by direct feeding to dogs' (NRC, 1985).10
That disappointed and angered the Industry.
The response of the pet food industry to the change in the 1985 NRC report, to the all-important caveat that a simple 'meets or exceeds' is unacceptable and that dog feed protocols may be mandatory, ranged from disappointment to anger. The AAFCO regulatory officials have yet to make a firm decision on this point in spite of the fact that they had two years advance notice that these changes were coming. Until they do decide, all label claim regulations will continue to use the 1974 revision as their guide.11
With AAFCO's current position feeding trials are no longer required. (With AAFCO setting the standard, not even the 1974 NRC revision continues as the guide.) The larger pet food companies may do some, but the smaller companies are likely to conduct no feeding trials. AAFCO did some feeding trials on three generic pet foods. It believes that no additional trials are necessary if the manufacturer uses the formula of any of these generic foods. That poses severe limitations, however.11
The Need for
Manufacturers can legitimately claim foods are balanced or complete only by feeding them with no other source of nourishment. Testing must show that the food is satisfactory for whatever claims are made. The claims include maintains weight for normal animals; satisfactory for normal growth from weaning to maturity; and satisfactory for female fertility, gestation, and lactation. The pet food industry chooses not to mandate feeding trials, however. They are currently solving this dilemma with NRC by no longer following NRC recommendations but by using their own approach that is officially sanctioned by AAFCO. The pet food industry through its own committee, AAFCO, abandoned the NRC oversight of pet food adequacy in order to avoid the costs of evaluating any diet. There are many small manufacturers of pet foods who do not conduct protocol feeding tests. Such testing costs $7,000 to $10,000 per diet. Furthermore they are likely not to completely analyze a diet chemically which costs about $2,000.
Establishing Nutritional Adequacy
Diets cannot be formulated to have optimal nutrient levels merely by using results from nutritional studies such as those reported by the NRC; only feeding studies determine adequacy for any commercial pet food.1 Many pet foods are largely based on cereals as their source of proteins. Cereals are very deficient in at least one essential amino acid, lysine. Manufacturers mix meat products with cereals so the final product has adequate amounts of lysine. It can be added by using meat and bone meal, but this product can also be deficient in lysine. The deficiency is evident by feeding trials or chemical analysis of the final product, something that many manufacturers do not conduct. Pet foods can also be deficient in available trace minerals such as iron and copper. These minerals are usually added in the form of their salts. Copper and iron absorption and use varies according to the form used. Thus, one form may be so poorly absorbed that the diet is deficient even though the total amount may exceed NRC requirements. That may also cause the producer to add a great excess to assure no deficiency but the excess can also be toxic. Feeding trials are needed to answer these problems. Without analyses and feeding trials, the diet is deficient even though it can be labeled as complete and balanced. Nutrients in a food can also be inadequate because of their interactions. Excess of one essential nutrient can induce another’s deficiency. For example, the need for vitamin E increases on feeding high levels of polyunsaturated fats. High levels of calcium increase requirements for zinc and can induce zinc deficiency. Diets containing excess zinc increase the requirement for copper to prevent copper deficiency. Chemical analysis of diets do not reveal such inadequacies.
Nutritional studies such as those reported in NRC's Nutrient Requirements of Dogs may not establish nutrient requirements for another reason.1 The least amount of a nutrient such as histidine for supporting maximum growth is not enough to maintain hemoglobin concentration or to prevent cataract formation.1 Thus, there is not merely one requirement for a nutrient. There is a whole range of requirements that depends on the need in every body system and the animal's needs for physiological performance. The minimal requirement for a growing animal is that which promotes maximal growth without regard to needs of specific tissues. To be concerned with what happens in all body tissues it is necessary to test pet foods in feeding trials. Formulating a diet from AAFCO recommendations cannot serve that purpose. Diets cannot be formulated theoretically; any such formulation is too imprecise for meeting animals’ needs. Industry knows that diet formulation to produce complete and balanced diets is imprecise, so it employs safety factors and adds excess nutrients. Is that justified?
Does an intake of a nutrient in excess of the nutritional requirement promote greater health than at the requirement? When diets are prepared to contain just the minimal amount of a nutrient there is always the risk the minimum will not be achieved because of natural variation in nutrient content of foods, bioavailability of the nutrient and the individual nutrient requirement. Therefore it is potentially dangerous to formulate diets just at the minimum. On the other hand, most nutrients in excess are toxic and so a huge excess of a nutrient is generally not appropriate. Some nutrients such as methionine have a very narrow range between requirement and toxicity, others such as the B vitamins have a wide range between requirement and toxicity.12
If this statement is true, Industry should use NRC recommendations to formulate the best balanced and complete diet followed by feeding trials to prove its adequacy. If this statement is true, Industry can begin to formulate the best balanced and complete diet by following NRC recommendations. But only feeding trials can prove adequacy for any diet. Dogs and cats consumed complete diets during years that they hunted for food; they could choose what they ate. After domestication, these animals were fed foods that humans ate. With agriculture’s development, dogs were fed grain-based diets. They developed many deficiencies. Then people also did not eat complete and balanced diets. Today people know how to prepare balanced diets. The nutritional needs of dogs are similar to human requirements. Therefore people can formulate balanced diets for dogs by using foods for human consumption. It is not necessary to feed a commercial pet food to provide a complete and balanced diet. People know how to balance diets and do not need to be dependent on commercially formulated diets.
What Should a Pet be Fed?
If feeding a balanced or complete diet does not insure that nutritional needs are satisfied, how should a pet be fed? The answer is not obvious even with the many different commercial pet foods that are balanced and complete. Consider what an animal nutritionist has to say:
Because nutritional decisions are multifactorial, often there is no one simple answer, and there is no one best diet for any species. There is no one best diet for a dog―the food which is optimal for the puppy is not optimal for the adult dog and vice versa. Therefore, to use nutritional science you have to consider all factors involved and weight them accordingly. Thus, there may be more than one solution depending on the weight given to various factors. This makes the application of nutrition frustrating to those individuals who expect "yes-no" answers.12
Owners feeding commercial pet foods have no choice but to accept manufacturers’ claims. If the balanced and complete claims cannot be trusted, owner-prepared diets should be fed. This gives preparers complete control over diet quality.
Pet Food Quality
Three factors determine pet food quality. Already discussed is a diet’s adequacy for required nutrients so that it causes neither deficiencies nor excesses. The source of a food's nutrients is a second factor. What are the food sources for pet foods? Nutritionists agree that producers should use only wholesome ingredients in formulating a commercial pet food. A third factor is non-nutrient ingredients added to improve a product's physical appearance or shelf life.
Manufacturers tell consumers that they can determine a product’s quality by reading its label. The U.S. Food and Drug Administration, Federal Trade Commission and AAFCO establish labeling regulations. These regulations require that labels contain: (1) each ingredient listed in descending order of their respective amount by weight and (2) a guaranteed analysis of the minimum amount of crude protein and fat, the maximum amount of moisture and crude fiber, and the added minerals and vitamins. The ingredient list provides some useful information for the purchaser selecting a food to feed a small animal pet. The label does not give amounts of each ingredient, however, which, according to regulations is not necessary. The pet food industry states:
When properly read and understood the pet food label should enable both the veterinarian and the pet owner to make wise judgments on a proper diet for the family pet.13
An animal nutritionist's evaluation of this label regulation and usefulness is different.
The required labeling of pet foods, in fact, provides little help to the pet owner....
...even for trained nutritionists, the labeling of a product is of limited usefulness in an overall evaluation of its nutritional value. Labels should produce more information about the digestibility, absorption, and utilization of protein; about the actual amounts of fat and its source, and about carbohydrate, minerals and vitamin content. With this information, the veterinarian can then provide improved service to his clients and protect them from the hazards of attempting to evaluate the information provided by commercial companies or by the label which is currently provided more for sales purposes than for service.4
Thus, the guaranteed analysis provides little useful information for making decisions on a commercial pet food. A pet owner cannot know if food described on a label may be a good choice to feed.
Pet Food Ingredients
Pet food manufacturers believe that standards of quality are acceptable when the product’s ingredients contain nutrient amounts listed on the label. Commercial pet foods contain ingredients that dogs and cats were not designed to eat, however. A representative list of ingredients for dry dog foods shows them to contain ground corn, soybean meal, meat and bone meal, other cereals and animal fat in descending order. Canned dog food ingredient lists show them to contain meat by-products (liver, kidney, lungs, etc.), meat (muscle), cereals (mainly wheat, barley, and oatmeal), and soy flour or grits.
Cereals make up the bulk of dry dog (60%) and cat (50%) foods. To that primary source of carbohydrate, meat (and bone) meal and soybean products are commonly added as protein sources, together representing up to 30% of the diet for dogs and 40% for cats. Animal fats, vitamins and minerals, and additives are added to complete the diet. Canned and semimoist foods vary some in the percentages and sources of cereals and protein. It is apparent that dog foods contain nutrients primarily from vegetable sources. Cost dictates the source of the ingredients. The source is justified by the idea that dogs and cats can adapt to almost any foodstuff making up their diet.
The dog is intrinsically one of the easiest animals to feed, a carnivore turned quasiomnivore through 10,000 years of aping man. This adaptability has permitted the marketing of dog foods that differ widely in ingredients, nutrient composition, and energy density. ...nutritional disorders are not likely to be encountered in dogs fed the main types of commercial products in appropriate ways.14
Although dogs may have become quasiomnivores, anatomically and physiologically they (also cats) are still carnivores. Their feeding preference is for meat. They have teeth designed to tear flesh and a short and simple gastrointestinal tract, one suited for digestion and absorption of a meat diet. Dogs and cats are not designed for being vegetarians but they are fed on the premise that they can eat anything humans eat.
Quality is low for most pet food ingredients, however, because their digestibility is lower than food for human consumption. Quality for a food's protein has been studied the most.
Quality of Protein in Pet Foods
One commercial company that manufactures drugs for the veterinarian recognizes a lack of quality in most commercial pet foods. Protein is maybe the most important nutrient in pet foods. This drug company criticizes pet foods' protein content by writing the following in their advertising copy:
However, not all protein sources are of equal value to the carnivore, and the quantity of protein in a commercial pet food often says nothing about its quality. Before domestication, dogs and cats hunted their prey and consumed a diet very high in meat protein, low to moderate in fat, and low in carbohydrates. This diet provided both the proper quantity and quality of protein for the carnivore's unique digestive system. Unlike an omnivore, whose digestive system consists of a fairly large small intestine and relatively small stomach, the carnivore's system consists of a fairly large small intestine and relatively small stomach. Thus, a carnivore's optimum diet must be concentrated, highly digestible, and low in residue because its body is designed to digest primarily protein. If an excess of carbohydrates and fats is included in the diet, much of what the carnivore eats is only partially digested by the time it reaches the large intestine for fecal formation, overloading the digestive and excretory systems....
Near the turn of the century, most commercial pet foods included a high percentage of meat protein and were low in carbohydrates, approximating the diet pets ate in the wild. When the Depression struck, however, it became prohibitively expensive to include high-quality protein sources in commercial pet foods. Low-cost, low-protein ingredients were substituted, and fillers high in carbohydrates, such as grains, replaced meat and fish proteins. Thus, pet owners began feeding their carnivorous pets diets better suited to an omnivore's digestive system.
Today, a whole industry has arisen around the production of "better" or "scientifically formulated" pet foods, which attempt to correct the gross nutritional imbalances in generic and off-brand pet foods. However, even the best pet foods, which contain considerable more high-quality protein than generic brands, are not perfectly balanced for maximum nutrition. They may be lacking in certain amino or fatty acids, or contain nutrients in such a low quantity that the animal would have to overeat regularly just to meet NRC minimums. Conversely, they may contain unbalanced excess of other nutrients. A recent survey compared a well-known canned dog food with the leading dry dog food, both of which claim to provide "balanced" nutrition. The digestibility claim of the canned food was approximately 90%, while the digestibility of the dry food was rated at 80%. The biological value of the protein content (in other words, how useful the protein is to the animal) was given as 69% for the canned food and 60% for the dry. Net utilization (the amount of food used by the animal in relation to the amount provided), can be calculated by multiplying digestibility by biological value. The results: 62% net utilization for the canned dog food and 48% for the dry. This means a dog would have to eat nearly twice the volume of either commercial food to achieve the net utilization that higher, more digestible sources of protein would provide. Furthermore, a 1984 pet food study revealed that 83% of 78 generic dog foods tested failed to meet NRC standards for analyzed nutrients, and 51% of the samples tested failed to meet their own label-guaranteed analysis. The study further revealed that the growth rate and health of puppies were severely affected when they were fed a diet of nothing but low-priced, dry commercial dog food.15
More details of pet food inadequacies are described in the nutrition literature.11 The pet food industry may believe that the quality of ingredients and the final product are acceptable. The last 20 years has shown the pet-owner public that both nutritional and medical disorders developed with the feeding of commercial pet foods, however.
Quality of Pet Food Ingredients-Wholesomeness
The consumer has an additional interest in pet food quality, one that is based on esthetics. Pet foods contain ingredients that people will not or cannot eat. Can a quality commercial pet food contain these ingredients and be "wholesome"? Few people are likely to object to a variety of cereals in diets for their cats and dogs. The sources for animal proteins, if known to the consumer, are likely to be objectionable to most, however. For example, meat and bone meal is the second most abundant ingredient for many popular dry pet foods. Most people do not know that meat and bone meal is prepared from (rendered) animal carcasses some days after death. Any animal protein considered inedible for human beings becomes an ingredient for pet foods or for making fertilizer. It is difficult to consider this ingredient wholesome. Commercial pet foods contain unwholesome ingredients.
What conclusions can be made? Industry tells the consumer:
Providing a pet with maximum nutrition doesn't mean merely supplying an adequate daily amount of commercial pet food or supplementing it with treat-type vitamin/mineral tablets. Nor does feeding a pet a scientifically formulated prescription diet ensure that its maximum nutritional needs are met. The fact is that no commercial pet food, no matter how balance or how high-quality its ingredients, can meet the nutritional needs of every pet. Each animal has its own unique nutritional needs based on age, size, and level of stress. The only way to meet those needs is by supplying a carefully balanced amount of all required nutrients in doses that can be customized for any cat or dog.15
Does this mean that it is difficult to meet an animal's nutritional needs by feeding a commercial pet food? From industry's conclusion above one appreciates that nutrition has profound effects on the health and longevity of dogs and cats. So the consumer should have an interest in pet food quality to maintain a pet's normal health. Commercial pet foods can be responsible for many health problems. Problems can develop when nutrients are in excess or deficient. That may seem surprising in an era where the pet food industry claims that "more is known about the nutrient requirements of dogs than of man's."16 Excess or deficiency is more likely for a food’s vitamin and mineral or salt content. Major nutrients are also sometimes sufficiently imbalanced to cause health problems. One such problem, hip dysplasia, is more likely to appear in larger breed dogs when their owners enhance growth by feeding foods designed to promote growth. As another example, feeding cats a commercial canned cat food to manage urinary tract problems contained inadequate amounts of taurine so that some cats developed cardiomyopathy. A variety of these problems are described later.
The quality of pet foods may be the most important factor in many common medical and surgical problems. Gastrointestinal diseases, especially those causing chronic vomiting and diarrhea, represent 35% to 40% of all the problems seen in cats and dogs. Before 1950 when pet owners seldom fed their pets commercial pet foods (they fed them mostly owner-prepared foods, the incidence of gastrointestinal problems was much lower than it is now. Skin diseases are common problems in dogs and their incidence in the past was much lower than it is now. Many skin problems are allergies to something fed; such allergies were infrequent in the past.
Some of these gastrointestinal and dermatologic problems develop because of recommended feeding practices. The pet food industry formulates puppy and kitten foods but they are nothing more than formulations for adult animals containing higher amounts of protein. These commercial foods are usually available to puppies and kittens when their eyes open, about two weeks of age. Common sense if not scientific knowledge tells us to not feed human infants as if they are merely little adults. Instead of feeding diets for adults, parents gradually introduce infants to the large variety of foods eaten by the human adult. The basis for feeding young pets should be no different. Feeding young animals to prevent future medical problems is discussed later.
The design and manufacture of commercial pet foods are still constrained by the specifications and criteria the industry establishes for itself. A pet food may be formulated using formulas that have been used to produce a food similar to a company's other products but even though they may use AAFCO's profile statement on their labels, a commercial pet food "most probably has not been subject to a feeding trial." Also feeding directions are required on all "complete and balance" products labels, although the ranges of recommended feeding amounts are often too broad to be useful. The American College of Veterinary Nutrition proposed that AAFCO require calorie content statements on commercial pet foods but 5 years later AAFCO has not adopted this proposal. The quality of a food and the amounts of commercial pet foods to feed thereby remain an estimate for the pet owner.17
References and Notes
1. Morris, James G. and Quinton R. Rogers. 1994. Assessment of the nutritional adequacy of pet foods through the life cycle. Journal Nutrition. 124:2520S-2534S.
2. Grunberg, Rosaly. 1995. Nutrition and disease. Petfood Industry 37(5):50.
3. Bryant, Vaughn M. 1995. Eating right is an ancient rite. The World and I. 10(1):216-221.
4. Newberne, Paul M. 1974. Problems and opportunities in pet animal nutrition. Cornell Veterinarian 64(2):159-177.
5. Buffington, Charles A. and LaFlamme D. P. 1996. A survey of veterinarian’s knowledge and attitudes about nutrition. Journal American Veterinary Medical Association 208(5):674-675.
6. Garvey, Michael S. 1984. In Canine Nutrition & Feeding Management, 2-3. Lehigh Valley: ALPO Pet Center.
7. Alpo Advisory Board. 1984. In Canine Nutrition & Feeding Management, 7. Lehigh Valley: ALPO Pet Center.
8. Earle, Kay E. and Philip M. Smith. 1993. A balanced diet for dogs and cats. In The Waltham Book of Companion Animal Nutrition. edited by Ivan. H. Burger, 45-55. Oxford: Pergamon Press.
9. Simpson, James W. 1992. Acute diarrhea in the dog. A monograph provided as a service to the veterinary profession by Waltham, World Authority on Pet Care and Nutrition.
10. Kronfeld, D. S. and C. A. Banta. 1989. Optimal ranges of actual nutrients. in Nutrition of the Dog and Cat, edited by I.H. Burger and J.P.W. Rivers, 27-34. Cambridge: Cambridge University Press.
11. Sheffy, Ben E. 1989. The 1985 revision of the National Research Council nutrient requirements of dogs and its impact on the pet food industry. In Nutrition of the Dog and Cat, edited by I.H. Burger and J.P.W. Rivers, 11-26. Cambridge: Cambridge University Press.
12. Morris, James G. 1995. Nutrition and Nutritional Diseases In Animals, 1-5. Class Notes For Veterinary Medicine 408, School of Veterinary Medicine. University of California, Davis.
13. Alpo Advisory Board. 1984. In Canine Nutrition & Feeding Management, 54. Lehigh Valley: ALPO Pet Center.
14. Kronfeld, D. S. 1975. “Nature and use of commercial dog foods.” In Diet and Disease in Dogs, edited by D.S. Kronfeld and D.G. Low, 20-31. University of California, Irvine.
15. A User's Manual for ProBalance Maximum Nutritional Supplements, Norden Laboratories.
16. Corbin J. E. 1972 “Nutritional requirements of dogs.” In Canine Nutrition, edited by D. S. Kronfeld, 1-12. University of Pennsylvania.
17. Dzanis, David A. 2009. Nutrition in the Bitch During Pregnancy and Lactation. In Current Veterinary Therapy XIV, edited by J.D. Bonagura and D.W. Twedt, 1003-1007. St Louis: Saunders Elsevier.