Think of a large, profit-driven industry with a history of high profile advertising campaigns, expensive product promotions and giveaways. It has powerful lobbyists. It responds quickly and decisively to negative media attention. It has denied for years that harmful carcinogens or other health hazards are in any of its products.

If the pet food industry didn't come immediately to mind--it should have. Pet food manufacturers proudly portray themselves as caring and conscientious providers of complete and balanced nutrition for our pets, despite many indications to the contrary.

In order to demonstrate the scope of the pet food industry, we need to look first at the process of recycling by-products from food produced for human consumption. By-products from human food production are meatless animal and poultry carcasses, waste from crops such as the husks, cobs, and stalks left over from processing corn and grains, old restaurant grease and much more, and all are transformed into usable products. This process of recycling by-products is called "rendering."

The first stage of rendering by-products is pulverizing and transforming bones and other hard substances into powders. Some of them are dissolved with acids. Sometimes the product is rendered further and processed into ash. Bleaching agents may be used to halt or eliminate the smell of decay. Second, moist raw materials are dehydrated, while feathers and other hard-to-breakdown by-products are hydrolyzed. "Hydrolyzing," simplified, is using heated sulfuric acid under tremendous pressure to dissolve and break down feathers, etc., into base sugars, thereby creating a digestible ingredient included in livestock feed (and pet foods) from something previously indigestible.

In the third phase, the raw paste and powder materials are blended together in specified amounts and then transferred to an "expander." Hot water or steam is added to the expander and the mixture is compacted through intense pressurization and heat. Fourth, the mixture is extruded (like using a caulk gun to push caulk out through the narrow opening) and sliced rapidly into individual pieces. Fifth, the pieces are usually sprayed with oils that may contain flavorings, vitamin supplements or other chemical additives, and then the pieces are dried for packaging. This is now livestock feed. Or dog food.

William D. Cusick, author of Canine Nutrition & Choosing the Best Food for Your Dog, spent decades researching pharmaceuticals and canine nutrition. Mr. Cusick, a self-proclaimed "animal advocate" who is semi-retired, shared some stark truths about rendering, recycling and dog food manufacturing.

Cusick said, "When the dog food companies advertise their foods they show a whole chicken or talk about the first ingredient being 'real lamb' or 'made with beef.' The pet owners then fill out the rest in their minds. They picture parts used from the 'whole chicken' as the part they themselves would eat, not the feathers, which, after all, really are part of the 'whole chicken.' Or they see a slab of meat in their minds, be it lamb or beef, and they are not picturing the bloody entrails mixed with sawdust."

In livestock production, there is a concerted effort to achieve quick livestock growth for low cost so consumers have affordable meat available in supermarkets. Recycled by-products are clearly a practical and economical solution that also resolves an otherwise huge waste-disposal problem. But there is a big difference between Daisy the cow and Lassie the pet; livestock are raised short-term as a food source, while pets are kept long-term for companionship.

By-product-rendered food is an accepted feed source for livestock that are slaughtered before experiencing health-related consequences, but the presence of rendered by-products in dog foods appears be a terrible mistake.

Commercial pet foods have been available for about 80 years. Nations with generations of dogs raised on commercial pet food have experienced substantial decreases in canine longevity: up to 50 percent in some instances and breeds, according to Cusick, along with alarming increases in cancers, reproductive complications and other health-related concerns. Hypotheses offered for these changes: environmental pollution, pesticides, vaccinations, urbanization, fluoridated water, and, of course, commercial pet foods.

In economies with a history of commercial pet food availability and consumption, including ours, human longevity has increased as canine life expectancies have markedly decreased-although humans and their companion canines share the exact same environment. Accordingly, decreases in life expectancy have not been documented in canines raised where commercial pet foods have never been available. When pet owners express concerns over pet food nutrition or ingredients, including known or suspected carcinogens, their concerns are generally ignored or discounted by pet food manufacturers. Hills-Science Diet did not return my calls. A local Iam's representative did, but refused to be quoted.

Pet owners want convenient and affordable food for their pets and the rendering industry readily supports the pet food manufacturers in satisfying the demand. Veterinarian Norman Ward, D.V.M., at Scottsdale's Holistic Animal Center of Arizona, shared his thoughts on manufactured pet foods.

"They take waste products and render them useful," Ward said. "But in an ultimately profit-driven business, safety and quality are destined to suffer."

"We are getting what we asked for," said Cusick, "but unfortunately, a discrepancy exists between what we are told we are getting and what we actually get."

In Alternative Animal Products: The Industry, the National Renderer's Association explains the need for rendering by-products: "Approximately 50 percent of every animal used for human consumption is inedible and must be dealt with in order for the cycle to continue. Also, fallen animals must be removed from the environment in a safe and acceptable manner. Total volumes of inedible raw materials from animal production are enormous and vary only when consumption patterns change."

According to National Renderer's Association statistics for 1991, 36 billion pounds of livestock and poultry carcasses were processed (rendered), along with billions of pounds of agricultural by-products, restaurant grease and more.

To get an idea of one person's annual by-product volume, picture two cow carcasses in front of you. Arrange about 30 chicken carcasses around it. Add half a pig or so. Toss with the contents of 40 large grass-and-leaf bags filled with corn stalks, grain husks, and vegetable and fruit by-products. Sprinkle the pile with a dozen or so decaying fish and garnish the top with a turkey carcass. Multiply the pile by your family members, and the resulting annual by-product pile would fill or overflow a 2-car garage packed floor-to-ceiling. Expand the concept exponentially to your city and then the entire country and it is clear that there are massive and varied quantities of food production by-products recycled each year by rendering facilities. But food-related items aren't all they recycle.

Maricopa County Animal Control euthanized about 20 percent of the cats and dogs that were brought to the county's two shelters in 1998-a total of more than 34,000 animals that were diseased, dangerous, disabled, or otherwise unfit for adoption. Thousands more are euthanized by other shelters, veterinary clinics and animal hospitals in the county. Just as food by-products need removal and disposal, so do euthanized animals and animals that have died from accidents, illnesses, or other causes.

Annie DeChance, a representative at the Maricopa County Department of Animal Control Services, said, "We take the carcasses to landfill where they are buried. Incinerators are quite expensive, something we have not been able to work into the budget yet."

Unfortunately, the nation has veterinary clinics and shelters, both public and private, without a budget for incineration or landfill-disposal costs. Unable or unwilling to pay by the pound for landfill disposal, some provide rendering facilities with dead animals-and make money by the pound when they do. Other clinics and shelters pay disposal services to remove dead animals and assume (or are told) that the bodies will go to a landfill or incinerator-when they may actually go to rendering plants. Such disposal services can be very profitable; they are paid to pick up and dispose of the bodies, and then paid once again when they deliver fresh 'meat'. According to guidelines set forth in the National Research Council's 1974 publication, The Nutrient Requirements of Dogs, all mammals (other than humans) are legally allowable "meat" for rendering so long as they are not decayed. States can pass more restrictive standards, but only a few states don't allow rendering of "4-D" sources: dying, dead, disabled, or diseased tissues.

In The Nontoxic Home and Office: Protecting Yourself and Your Family from Everyday Toxins and Hazards, author Deborah Lynn Dadd writes: "Each year about 116,000 mammals and nearly 15 million birds are condemned before slaughter. After killing, another 325,000 carcasses are discarded and more than 5.5 million major parts are cut away because they are determined to be diseased. Shockingly, 140,000 tons of poultry is (sic) condemned annually, mainly from cancer. The diseased animals that cannot be sold are processed into animal feed."

And... Voila! ...canned pet food manufacturers gain an economical supply of real meats!

Diseased livestock and poultry destined for rendering often have metal ear tags or leg bands. Poisonous flea collars or identification tags are often left on pets. Such items are supposed to be removed before rendering, but often aren't.

Try to imagine yourself employed by a rendering plant and confronted with a small truckload of freshly euthanized dogs and cats. Your job is to see that the bodies are removed from the truck and loaded into rendering equipment. With protective gloves and a paper filter covering your nose and mouth, you are also supposed to ensure that collars, tags or other items are removed from the animals before the rendering process begins.

You walk around to the back of the delivery truck and tug upward on the sliding door. As it rolls upward you see a mottled, tangled mass of scraggly, mangy animals with staring eyes and lolling tongues. Swollen ticks come into focus on and around the bodies as hopping fleas dance before your eyes. Backing away in disgust, the nauseating smell of dirty animals mingled with the stench of death, urine and excrement slaps your senses and turns your stomach. Do you think you would be willing to touch those dead animals crawling with parasites to remove flea collars and dog tags by hand? Or do you think you would you want to get that pile of bodies into the machinery as quickly as possible?

The fact that flea collars and tags are not always removed before rendering is not surprising, but the end result is that poisons and metals can end up mixed in with the rendered flesh. And that includes strong pesticides from recent flea or tick dips. And yes, dead dogs and cats are considered "meat" by the rendering industry. Hopefully, they wind up in agricultural fertilizer for our plants, and not as pet food or livestock feed.

It would be logical to expect pet food ingredients to be labeled and defined in terms that any pet owner could clearly understand, with each and every item named and defined, but they're not. Approval of pet food ingredients and content definitions are determined by the Association of American Feed Control Officials, (AAFCO), a self-regulating association that sets the standards for all livestock feed and pet food contents and labeling in the United States. AAFCO labeling policies don't appear to be logical--unless you hold the opinion that the industry doesn't want consumers to clearly understand ingredient labels and have created misleading content categories by design.

"Of course they misinform and mislead us," said Cusick.

"They don't want pet owners to read dog food labels that say: This product contains no meat. Contains no whole grains. Consists mostly of filler that is recycled from by-products. Contains dangerous chemicals and carcinogens that have been added in an attempt to: try and keep it from growing harmful bacteria, stop it from going rancid, make it taste good enough so dogs will eat it, and give it a good color so it will appeal to humans buying it. And balanced nutrition is achieved solely by vitamin supplementation."

When asked how dogs could live on dog food, if it is really that bad, Cusick mentioned studies that had been performed on adult men who were given only water and vitamins. It was determined that men could live on vitamins and water, which sustained them for a period of months, but their health deteriorated and their life expectancies were shortened considerably. So if those men were given cardboard to eat with vitamins imbedded in it, they would have been able to fill their stomachs, alleviating hunger, while they also received a minimal level of nutrition to sustain them. And if they had never eaten real food, they wouldn't ever know what they were missing: just like our dogs with dog food.

Asked how deception on such a grand scale could be allowed to continue, Cusick responded with a possible solution to the problem.

"If the labels read the same, then the food inside should be the same. This is where, unfortunately, we need some laws written. Today there are no label laws that a pet food manufacturer is worried about. As the 1997- to -1998 President of the American Association of Feed Control Officials wrote me in an ongoing e-mail debate about lax labeling regulations in this country, 'the large manufacturers are protected by the constitutionally guaranteed right of speech, which doesn't require that speech be truthful or with reason.' Since the pet food industry is governed by the AAFCO, an association manned by people like the association president who made that statement--and not regulatory agencies with a set of laws to which they must adhere--we are dealing with products made and sold with only one rule: Buyer Beware," Cusick said.

When asked what the real differences are between the low-cost discount store dog foods and expensive premium dog foods, Cusick's response was disturbing but not entirely surprising.

"Premium pet food companies sell their foods at a higher price than grocery store pet foods and cite the 'so-called fact' that they cost the buyer more because they use better ingredients. Yet they use the same wording in their 'guaranteed analysis' labels or ingredient lists. So it is not a matter of asking ourselves if we are being mislead, but rather which pet food company is doing it. Either company 'A' is using misleading statements to get higher prices, or company 'B' is putting in lower-quality ingredients than company 'A' and falsely claiming the same ingredients. Read the labels and decide for yourself."

I did. Compare the attached ingredient labels from Science Diet, an expensive premium product available in many veterinary offices, and Ol' Roy, one of the least expensive dog foods available (in the table at bottom of article).

Cusick continued: "And canned food isn't much better. When it was discovered that some low-income retirees were eating canned pet foods a while back, nutritional values were analyzed. Canned foods start losing bio-nutritive values only 72 hours after canning and it takes six weeks, on average, for new cans to reach grocer's shelves."

Cusick explained how meat could lose nutrition inside a can, saying that protein can always be measured by nitrogen analysis, but the meats don't contain the same level of bio-nutritive-usable and easily metabolized-protein after they are canned. (As opposed to canned tuna or other fish that doesn't lose much nutritional value when canned.) Using only nitrogen analysis, cardboard would have 'protein', and so would a cell phone for that matter, so 'protein' is present, but if we ate cardboard or cell phones we wouldn't derive any more nutrition from them than our pets derive from 6-week-old canned meats.

With a note of weary patience in his voice Cusick said: "The pet food they eat isn't much different than eating cardboard, just worse for them. The food is comprised of waste products-something our society produces huge quantities of that are in dire need of disposal. But instead of burning it or burying it, they reformulate and package it, advertise it, mislead us about it every way they can, and then sell our own garbage back to us at a huge profit. Asking me to name a good pet food is like holding up different packs of cigarettes in a cancer ward and asking me which one is the best."

Unwilling to make any blanket statements about optimal percentages of proteins, fats, or carbohydrate concentrations for dogs, Cusick believes different breeds of dogs have individualized needs and cited studies and research results that proved it. Ideally, the nutritional needs and types of food for a dog should be calculated individually by breed, age, activity level, water source, stress level, gender, and living accommodations. During the final interview, Cusick helped with accurate descriptions for the following "visual" dog food recipe:

Start by imagining a large mixing bowl in front of you. Take some lamb bones and burn them into ash. Measure five cups of the ash into the mixing bowl, which will now look like the bottom of a full ashtray. Measure in four cups of rice husks that look like fingernail clippings and smell like beer. Grab three and a half cups of micro-pulverized barley husks, a dirty brown sand-like substance, and add them. Add three cups of hydrolyzed chicken feathers, which is a grayish powder. Now add two cups of pig excrement dissolved with heat and acids. Now pour in two sticky cups of corn gluten meal, a gelatinous liquid with a greenish hue. Add one cup of a green powder made from discarded soybean plants after the beans have all been picked and removed. Add a dash of carcinogenic flavor powders and a pinch of poisonous preservative. Add food coloring until the color appeals to your individual preference. Add one-eighth of a teaspoon of vitamin supplements, a yellowish powder. Don't spill any-this is what makes the food complete and balanced-and it is vital to the life of your pet. Mix the dry ingredients until moistened by the gelatinous green gluten. Add some rancid lard or bacon grease you forgot was under the kitchen sink so your dog will be able to palate the final product. Form into little round balls the size and shape of your dog's dry food pellets. Let dry or heat in oven to speed the process.

Congratulations: you have now made your own dog food that is comparable with some commercial brands! The ingredient label of our sample 'visual recipe' would read: Lamb Meal, Brewer's Rice, Barley, Poultry By-Products, Animal Digest, Corn Gluten Meal, Soybean Meal, with miscellaneous vitamin supplements, flavorings, food coloring, and preservatives. Bon Apetit!

A dozen vets around the Valley were asked their opinions on "what to look for and look out for in pet food." All of them responded that premium foods are best: more digestible and of better quality so your dog will eat less, poop less, and be healthier. While opinions differed as to whether or not human food should supplement a dog's diet, quite a few of them did mention that different breeds have different nutritional and dietary requirements. Unfortunately, veterinarian schools don't stress nutrition, so vets really don't get much training--sometimes as little as one day or less of nutrition classes for canines.

"Don't blame the vets," said Cusick, "they care just as much as we do and have been just as misinformed. Arbitrarily, the AAFCO can and has stopped requiring feed trials. The AAFCO can and has allowed dog food manufacturers to add a vitamin that is proven to be harmful for dogs because it is a cheap preservative (Vitamin C: dogs' livers already produce it), and cannot be held accountable in any way. The AAFCO is what we need to examine. Label laws are needed so consumers can actually make informed choices. And people will have to be willing to give up that convenient bag of dog food and to cook or buy fresh food for their pets. Informed consumers would force them to produce really good pet food-but it will cost a lot more if they ever do...and the pet food industry will fight it every step of the way. I do my part by sharing all this, one person at a time," said Cusick.

Cusick offers breed-specific recipes for balanced canine nutrition, derived from multiple studies done on canine breeds combined with his own research results, that are available (for a fee) from his web site. His web site also has informative articles and multiple related links. He finished the final interview with a softly spoken note of optimism, saying, "The tobacco industry has finally been held accountable, someday the pet food industry will be."

I threw all of the dog food out of our house and into the garbage while researching this article; it is back where it belongs. Until the recipes for balanced home-cooked dog food arrive by snail-mail, my dogs are eating the same things I do. By comparison with commercial dog food, human breakfast cereals (sans sugars), cheeseburgers, burritos and leftover pizza have turned out to be darn good dog food: at least the dogs seem to think so.

Note: Since this article was written, I have been making fresh dog food for my pets from human food sources/items and leftovers. My vet says my dog is in amazingly excellent health, but she could use to lose
10 or 15 pounds (she weighs 170). If you are interested in making your own fresh dog food and would like recipes, contact the expert, Cusick, or myself through Email.

Dog Food Comparison Table

Dog Food Ingredients

Poultry by-products- NO MEAT. (*****Products must list meat as an ingredient if they contain even 1 percent real meat.) By-products are produced in the course of making a primary food ingredient: a secondary or incidental product. Feathers can be removed from a carcass during production of poultry meat and then hydrolyzed (turned edible by using sulfuric acid and steam-pressure cooking). Hydrolyzed feathers are acceptable poultry by-products. Other by-products are the chicken carcasses, including feet, feathers, necks, undeveloped eggs, skin and intestines.

Meat by-products- NO MEAT. Do include any part of any mammal including lungs, brains, skeleton, bone, stomach, blood and intestines. Can be horse by-products or meat from any mammals. Beef by-products would be from cattle, lamb by-products from lamb, etc.

Fish by-products- NO MEAT. Do contain head, eyes, tail, fins, intestines, and blood.

Fish meal- No meat. Fish bones ground, pulverized or burnt into ash.
Poultry by-product meal- NO MEAT. Everything included in by-products except feathers-except for unavoidable minimal amounts.

Lamb/Beef/etc. meal- NO MEAT. (Basically just bones ground, pulverized or burnt to ash.) Does not include blood, hair, hoof, horn, hide trimmings, manure, stomach and rumen contents except for unavoidable amounts. Otherwise, it is the same stuff as by-products. Lamb meal is ground lamb bones, beef is ground beef bones, etc. Meat meal can be any combination of mammal bones. Animal by-product meal- HAS NO MEAT. Rendered animal tissue that doesn't fit any other ingredient definitions. Some kind of mixed by-product parts? Cannot contain extra bone, hair, blood, hoof, hide trimmings, manure, stomach and rumen contents.

Animal digest- NO MEAT. When an animal has digested food, think about what the food has become. This is animal digest. Made by rendering animal products which aren't included in any of the other ingredient descriptions and breaking them down with chemical or enzymatic hydrolysis for use in feed. Must be made soluble with the use of heat and moisture since these ingredients are not soluble in their natural state. Does not contain hair, horn, teeth, hooves, or feathers except in unavoidable trace amounts. (Conveniently does not say it must not contain manure, stomach or rumen contents.)

Meat and Bone meal- Tissue (YES MEAT) and bones rendered from any mammal. No blood, hair, hoof, horn, hide trimmings, manure, stomach or rumen contents except small unavoidable amounts included in processing. Can be diseased livestock or mammal meat from horse, dog, cat, etc.

Corn gluten- Corn residue. Sticky residual substance used to hold together rendered and pulverized composite of feed ingredients. The part of the commercial shelled corn that remains after the extraction of the larger portion of the starch, gluten and germ by the process employed in the wet milling manufacture of cornstarch or syrup.

Corn gluten meal- Corn residue. Sticky residual substance used to hold together rendered and pulverized composite of feed ingredients. Dried residue from corn after the removal of the larger part of the starch and germ and the separation of bran by the process employed in the wet milling manufacture of cornstarch or syrup or by enzymatic treatment of the endosperm.

Mill run or grain hulls, meal, middlings, or by-products- By-products and outer coverings of grains processed for human consumption. Does not include the more nutritious germ, flour or bran.

Brewer's rice- A rice residue. The dried extracted residue of rice that results from manufacturing liquid portions of malted grain. May contain pulverized dried spent hops in an amount not to exceed 3 percent.

Meat- The clean flesh of ANY slaughtered mammal. (Not likely in dry or canned pet foods unless from mammals that humans do not or will not consume such as diseased or condemned livestock, horse meat, dog meat, etc.) It may only be striated skeletal muscle, or tongue, diaphragm, heart or esophagus. It may include accompanying and overlying fat and portions of skin, sinew, nerves, and blood vessels that normally accompany the flesh. If a specific single type of meat is used, it must be defined, any combination of two or more allows "meat."

Digestibility Test- A test to see how long it takes a food solid to break down in a strong laboratory acid. Some companies claim that foods passing this test in the shortest time will provide the best nutrition. But the word "digestibility" is not synonymous with the word "nutritious." Just because a food solid can break down in a laboratory acid does not mean the animal eating it can nutritionally use (bio-nutritive value) that food. And not all dogs or cats have the same nutritional acceptance of food sources. This has been established by tests cited in the 1985 Nutrient Requirements of Dogs by the National Research Council. Chemical analysis is unreliable for determining whether a food will provide an animal with sufficient minimal nutrition, as it does not take it to account or measure palatability, actual digestibility, or biological availability (bio-nutritive value).

Actual Digestibility- A process for measuring the ratio of food consumed against the subsequent waste (excrement) produced that takes into account the metabolic water ratio and other variables. Not required by the AAFCO.

Propylene glycol- Also known as antifreeze. Derived from Propylene Glycol Monomethyl Ether. It is used as a solvent in acrylics, stains, inks and dyes. In humans it can have an anesthetic effect, cause headaches, nausea, vomiting, central nervous system depression, convulsions, liver damage, kidney damage, coughing, wheezing, breathlessness, loss of balance, coma and death. Experimentally exposed animals suffered all of the above as well as heart arrhythmia, respiratory failure, narcosis (profound stupor), growth depression, decreased blood pressure, and death. Known to cause illness in dogs, small amounts of this compound is used in some dog foods to tie up water content and maintain texture, thus inhibiting bacterial growth.

Propyl gallate- Manufacturers add this to retard spoilage but it is suspected to cause liver as well as other types of health damage.

Ethoxyquin- A pesticide and poison, it is seen in some pet foods and is sometimes conveniently mixed in by the rendering facility without the manufacturer "knowing" so that it isn't "required" to be listed on the label.

Sodium nitrite- Used as both a preservative and a red coloring agent, when used in food it can produce powerful carcinogenic substances known as nitrosamines.

Butylated hydroxytoluene (BHT) and Butylated hydroxyanisole (BHA)- These antioxidant preservatives have been linked to depression of white blood cells and to inhibition of both the immune system and glucose absorption. There are strict regulations and limits for use in human foods but not animal foods. BHT has also been implicated as a cause of liver damage, metabolic stress, fetal abnormalities and serum cholesterol increases.

Food colorings- Why are food colorings added to food for color-blind (or virtually color-blind) dogs to consume? Because pet food manufacturers believe they increase visual appeal for the humans buying the food and thus increase the sales. Artificial coloring does not require specific labeling in pet foods, which often contain Red No. 3, Red No. 40 (a possible carcinogen) Yellow No. 5, Yellow No. 6, Blue No. 6, Blue No. 2 (shown in studies to increase dogs' sensitivities to fatal viruses.)

Artificial and synthetic flavorings- Synthetic flavorings are grouped under artificial flavorings in pet foods and although minimal or no research or testing has been documented on many of them, and they are not allowed in human foods, the FDA has no jurisdiction over flavorings used in pet foods.

(Compiled by the author from: AAFCO Official Publication, 1994; Canine Nutrition, by William D. Cusick; The Holistic Guide for a Healthy Dog, by Wendy Volhard & Kerry Brown, DVM; Nutrient Requirements of Dogs, by the National Research Council; and Dr. Pitcairn's Complete Guide to Natural Health for Dogs and Cats.)

Related Texts With Applicable Web Site References

Alternative Animal Products: The Industry, National Renderer's Association, 1991. [http://www.inform.umd.edu/EdRes/Topic/AgrEnv/ndd/feeding/ALTERNATIVE_ANIMAL_PRODUCTS_THE_INDUSTRY.html]

Dr. Pitcairn's Compete Guide to Natural Health for Dogs & Cats, Richard H. Pitcairn, D.V.M., Ph.D. & Susan Hubble Pitcairn. Rodale Press: Penn., 1995.
 

Waltham Symposium 7: Nutrition of the Dog and Cat, Editors I.H. Burger and J.P.W.Rivers. Cambridge University Press: New York, 1989
 

The Holistic Guide for a Healthy Dog, Wendy Volhard & Kerry Brown, D.V.M. Howell Book House: New York, 1995.
 

Nutrition of the Dog, Clive M. McCay. Comstock Publishing Company: New York, 1949.
 

Nutrient Requirements of Dogs, National Academy of Sciences, Washington, DC, 1974.
 

Nutrient Requirements of Dogs, National Research Council, Washington, DC, 1985.
 

(c) Copyright November 8, 1999, C. Clayton