Features July 1999 Issue

Finding The Best Dog Food Diet

Whether formulating a home-made diet or buying bags, itís important to customize the ratio of proteins, fats, and carbohydrates to suit your dog.

Every commercial dog food maker includes macronutrients – proteins, fats, and carbohydrates – in varying percentages in their products. But in recent years, some companies have begun formulating dog foods with higher percentages of protein and/or fat. While there is no regulated definition of the word “premium,” many of the companies who make high-protein or high-fat foods call these products “premium” foods, and tout them as more healthful for dogs than typical grocery store offerings. What is responsible for the move to higher fats and/or proteins in canine diets?

Just as with the field of human nutrition, waves of popular theory tend to sweep across the field of animal nutrition every few years. In the last 15 years or so, nutritionists have become occupied with the idea that the modern diet may be responsible for current levels of the major diseases seen in modern humans – cardiovascular disease, cancer, diabetes, etc. The advent of agriculture, some 10,000 years ago, they theorize, brought about radical changes in the human diet. Prior to organized agricultural practices, humans were nomadic hunter/gatherers. With the spread of agriculture, people began consuming two new groups of foods – grains and dairy products – and became more sedentary, a trend that deepened following the industrial revolution. Today’s human eats more processed foods than fresh, whole foods, and far more refined grains and sugars than ever before.

The key piece of evidence that this trend has been an unhealthy trend for humans can be found in studies of hunter/gatherers who are still living pre-agricultural lives; studies have shown these people to be completely free of the diseases named above. Further, as these hunter/gatherers have adopted modern diets – high in grains, carbohydrates, and dairy products – they began to develop the diseases so well known to us, most notably cancer and heart disease. A return to a diet modeled more along the lines of Paleolithic man, some nutritionists speculate, might result in less disease.

Every dog needs an individualized 'zone' to achieve and maintain optimum health.

Following this line of thought, some veterinary nutritionists theorize that many of our dogs’ ills have stemmed from their modern-day commercial diets, which have evolved more out of regard for the needs of food manufacturers’ and dog owners than the needs of dogs. Given that, genetically, our dogs are not much different from the dogs of Paleolithic times, putting them on a pre-domestication diet might be one part of restoring canine health to robustness.

Crossover Dog Food Diet Ideas

Barry Sears, Ph.D., made his fame – and presumably fortune – as the author of Enter the Zone: A Dietary Roadmap, in which he describes a diet plan that he developed after years of independent study. A former MIT researcher, Sears tweaked some of the concepts behind the “Paleolithic diet” and determined that for maximum health, humans should eat a diet that is comprised of 30 percent protein, 30 percent fat, and 40 percent carbohydrates. The “Zone Diet,” as it is now referred to, has its share of critics, as well as thousands of enthusiastic adherents, at least one of whom has applied Sears’ basic concepts to canine nutrition.

In the first part of this two-part series (“Fat, Protein and Carb Levels in Dog Food,’” WDJ May 1999), we stated that it was interesting that as yet, none of the canine nutrition experts had begun promoting a “canine Zone” diet, but we were wrong! Celeste Yarnall, PhD, animal nutritionist and author of the 1998 book, Natural Dog Care, concurs with Sears regarding several integral aspects of Zone dieting. In fact, Yarnall consulted with Sears when preparing her recommendations for canine diets, and feels that Sears’ “Zone” ratio of 30 percent protein, 30 percent fat, and 30 percent carbohydrates is a healthy prescription for canine diets.

However, we’re of the opinion that there are not just one, but several healthy dog “zones,” primarily due to the fact that there are a number of factors that should determine the percentages of protein, fat, and carbohydrates – as well as the micro-nutrient levels – in any given dog’s diet. The dog’s age, size, state of health, work load, and environment should all be taken into consideration in determining his diet.

High-Fat Diets for Dogs

Most veterinary nutritional literature recommends a range of five to 20 percent fat for most dogs. Sears’ Zone Diet (and Yarnall’s identical recommended ratio of proteins, fats, and carbohydrates for dogs) contain considerably more fat (and more protein) than most dogs who eat commercially prepared foods (without additional supplementation) generally receive. There are a number of dogs who can benefit, in our opinion, from high-fat diets. In particular, super-athletes (dogs who pull sleds, hunt extensively, run long distance with their owners, etc.) can benefit from a higher percentage of fat in their diets. In order to perform these strenuous activities, these dogs require more total calories than their sedentary brethren; a high percentage of fat in the active dog’s diet seems to provide the additional calories thanks to a uniquely efficient process called “fat adaptation,” a process whereby the body “learns,” over time, to break down and utilize dietary fats especially effectively.

Hilary Watson, an Alaskan dog sledder and a major proponent of high-fat diets, explains: “A high-fat diet, in conjunction with endurance training, causes cardiovascular, pulmonary, and enzymatic changes that enhance the ability to use fatty acids as fuel for muscle activity. This is known as ‘fat adaptation.’”

Author and nutritionist Celeste Yarnall is a fan of the Zone Diet; Sears praises her canine adaptation of his human diet formula.

Stresses (from physical exertion, to environmental or psychological stress) increase a dog’s requirement for energy as well as non-energy nutrients. High-stress or -performance diets should be high in metabolizable energy, which a high fat content can help provide. Fat is high in energy density and digestibility, providing about 2.5 times more energy than any other nutrient. Working dogs exposed to a variety of stressful situations including racing, hunting, police duty, guiding, and extensive showing, as well as dogs that experience extreme ambient temperatures, would especially benefit from higher-fat diets.

The importance of diet in one form of stress, such as exhaustive physical activity, is emphasized by a 1980 study in which four diets (three commercial and one experimental) were compared by the endurance performance of Beagle dogs on a treadmill. Digestible fat intake was positively correlated with endurance performance, but there was no significant association between digestible protein intake and performance. Carbohydrate content was also varied in the diets associated with these endurance tests, but results were inconclusive.

To feed for weather extremes such as Arctic temperatures, sled dog handlers must increase their dogs’ rations; wind chill factors in open areas can increase the dogs’ energy needs by 70-80 percent!

Dietary energy needs also increase with high temperatures and humidity. Tropical climates increase the calories expended for cooling, and reduce the dog’s desire to eat, so more calories are required in fewer grams of diet. Especially large active breeds of dogs may also benefit from diets with higher percentages of fat. These dogs may need extra calories to maintain adequate body weight. Dogs who have cancer can also benefit from a diet containing a high percentage of fat (see “Special Diets for Dogs with Cancer,” WDJ December 1998). Of particular importance is that dogs with cancer NOT receive diets high in carbohydrates; recent data from studies by leading canine cancer researcher Dr. Gregory K. Ogilvie of the Colorado State University, Fort Collins, School of Veterinary Medicine, suggest that cancer thrives on carbohydrates.

Considerations for Dogs with Cancer

The one worry about feeding a high-fat diet to dogs – including dogs with cancer – is that the fat will make them feel full before they have eaten enough food to meet their needs for vital calories and micronutrients. “If the percentage of dietary fat is too high, the dog will stop eating before he has met his nutritional requirements, which can cause a nutritional deficiency to develop,” warns Donald R. Strombeck, DVM, Ph.D., Professor Emeritus at the University of California at Davis School of Veterinary Medicine, author of the 1999 book, Home-Prepared Dog and Cat Diets.

Strombeck's book offers more than 200 recipes for homemade diets, complete with information about the calories, fat, and protein contained in each diet.

For this reason, Dr. Strombeck recommends that anyone who feeds their dog a high-fat diet ensure that the food sources are of the highest quality. A highly digestible, nutrient-dense food is especially important for canine cancer patients, who may have a poor appetite; what little food they eat should be as nutritionally beneficial as possible, not full of “empty” calories.

There isn’t much agreement among veterinary nutritionists regarding high-fat diets for ordinary dogs. “No one knows the cardiovascular effects of feeding a high-fat diet over long periods of time to average dogs,” cautions Marty Fettman, DVM, of the Colorado State University, Fort Collins, School of Veterinary Medicine. “Feeding trials must be generational in length before we can judge the costs or benefits of feeding such a diet to dogs.”

There are a few cases where it might be helpful to restrict a dog’s dietary fat. Dogs who frequently suffer diarrhea may benefit from a lower-fat diet.

Inadequate dietary fat may lead to a fatty acid deficiency and /or an energy deficiency resulting in poor growth, weight loss, and reduced physical and reproductive performance. Insufficient EFAs can also lead to impaired wound healing, cause a dry and lusterless coat and scaly skin, and changes in the lipid film on the skin, which in turn may predispose the animal to skin infection. Dermatitis may ensue (a localized infection in the external ear canals and between the toes), or can erupt anywhere else on the body in lesions called “hot spots.”

Interestingly, EFA deficiencies can occur in dog who receive foods that are manufactured with adequate fat. This can happen when the EFAs are oxidized due to over-long storage or poor storage (warm or humid) conditions. To avoid buying pet food that has been stored too long (and which has suffered some degradation of its ingredients), try to buy from retail outlets with high turnover, or even, direct from the manufacturer, if possible. Buy only enough food to feed your pet for a month to six weeks, to ensure freshness. Store bags in the refrigerator or freezer, or at least a cool dry place to keep oils from rancidity.

High-Protein Diets for Dogs

The amount of beneficial protein in a food can similarly depart from the stated level on the food’s label. The American Association of Feed Control Officials (AAFCO) requires dog food makers to list only the crude protein contained in the food on the label, rather than the digestible protein. While some companies – generally the ones with higher-quality proteins in their foods – voluntarily list the amount of digestible protein in their foods, this is the exception, rather than the rule. Regardless of which fat/protein/carbohydrate ratio you are shooting for, determining the protein portion provided by your dog’s favorite food may require a little detective work.

Protein quality is judged by the protein’s digestibility and amino acid levels. The higher the biologic value of a protein, the less the amount of that protein needed in a diet to meet all of an animal’s essential amino acid requirements.

Because most proteins extracted from plant or grain sources are low in certain amino acids, most commercial foods combine animal tissues, cereal grains, and sometimes, soybean meal, to ensure a balance of complementary amino acids. Soy protein is nutritionally equivalent or superior to animal protein, providing high levels of most essential amino acids. When fed in combination with complementary sources of essential fatty acids, soy can provide excellent protein nutrition.

Meat protein sources should be as complete and wholesome as possible. The more processing that a meat is put through, the fewer vital nutrients it will contain. Vitamins and vital enzymes deteriorate with exposure to oxygen and with heat, so look for foods with turkey, beef, lamb, or chicken (preferably in the first three ingredients). Several big steps lower on the quality scale are products that contain turkey, beef, lamb, or chicken meal, which are ground, processed products. Several steps lower are foods that contain generic mixtures of several types of animal products, euphemistically called “poultry meal,” or worse, “meat meal.”

According to Dr. Strombeck, protein sources are the most likely ingredients in commercially prepared dog foods to be unwholesome. According to most holistic veterinary practitioners, home-preparing your dog’s food with top-quality protein sources is the only way to guarantee the digestibility and usefulness of the protein.

In particular, older dogs can benefit from higher percentages of protein (and higher quality protein), largely because they are less efficient at processing the proteins.

However, total dietary protein should be restricted for dogs with chronic kidney disease, since processing protein exacts a toll on the kidneys. Protein should also be reduced for dogs in recovery from acute pancreatitis, since protein can trigger pancreatic secretion. The small amount of protein that is fed to these dogs, then, should be of the highest quality possible. Carbohydrate controversies

Most commercial dog foods include either corn, wheat, rice, or any number of combinations of these grains in their products, largely because these foods are less expensive than other sources of dietary energy and certain nutrients. This means that most commercial dog foods contain high percentages of carbohydrates relative to the amount of protein and fat. But despite the pet food industry’s reliance on grains, there is quite a bit of controversy as to whether dogs need or should even have carbohydrates. Neither the National Research Council (NRC) nor AAFCO makes recommendations for a dog’s carbohydrate daily requirement.

Canine (and feline) nutrition specialist Celeste Yarnall and “Zone Diet ” developer Barry Sears agree on the ideal “Zone” ratio for dogs, and concur that humans and hounds alike eat way too many carbohydrates. One of the most obvious differences between the diet of today’s domesticated dog and the ancestral diet of the wild dog is the heavy consumption of carbohydrate-laden grains.

Insoluble carbohydrates (fiber) tend to pass right through the animal. Diets high in fiber may be appropriate for dogs who tend to eat too much, since fiber absorbs water on its way through the digestive tract, which helps lend a feeling of fullness to the bored or food-obsessed dog.

High-fiber diets are inappropriate for dogs that have high energy requirements (growth, late gestation, lactation, stress, work), as fiber has been shown to decrease the absorption of nutrients and displace useful energy sources. Excessive dietary fiber is also associated with adverse effects such as the production of loose stools and flatulence. You may notice a proliferation of looser stools when feeding foods containing lots of fiber; this may include so-called “lite” foods, formulated for the aforementioned bored and obese dog.

Interestingly, studies have shown that both adult dogs and puppies (after weaning) can grow and thrive on diets containing almost no carbohydrates whatsoever – an astonishing fact, considering that some commercial dog foods (especially the most inexpensive brands) contain this macronutrient in excess of 60 percent.

As Dr. Strombeck reminds us, “You can expect that the least expensive dog foods will be largely comprised of cereal, and offer poor palatability and digestibility . . . You get what you pay for.”

Susan Eskew, a freelance writer from Crested Butte, Colorado, is a frequent contributor to WDJ.

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