Principles of Dog Nutrition

By T. J. Dunn, Jr., DVM

Pet nutrition principles for feeding dogs continue to evolve. An example of how far we've come concerns what we veterinarians, 30 years ago, used to call "All Meat Dogs." These pathetically sick and dying dogs were coming in to clinics all over the United States, thin, weak, with hair loss and metabolic imbalances as a direct result of eating a nationally advertised "All Meat" canned dog food.

Nearly everyone at that time thought that because dogs were carnivores (they're technically omnivores) that "all meat" diets must be the best thing for them! We know now that dogs cannot survive if fed 100% meat for extended periods.

Since then, pet food manufacturer's knowledge has changed and they now make some properly formulated foods. We've all learned much more about just what it takes to put together the right combination of ingredients in the proper ratios to create a nutritious diet. Unfortunately for the pet food purchaser, and worse for the dog, there are available all across the United States various brands of foods that, despite what the label may claim, are NOT a good source of nutrition for your dog. Some are actually harmful!

During my thirty years of veterinary practice I have often been upset by the poor condition I see some of my canine patients in due to inferior quality diets that the owner honestly believes to be adequate. In good faith the dog owner assumes that since the dog food label proclaims "complete and balanced", "premium", "high protein", and so on, that their dog will automatically do just great if that's all it is fed.

Because of ambiguous or deceptive labeling of the dog food, the owner unknowingly will feed an inadequate diet. And it may be decades before the FDA requires more strict guidelines for dog food manufacturers to follow so that misleading, ambiguous, and sometimes phony labeling practices no longer confuse or trick the purchaser.

For example, I could put together a "high protein" dog food where the protein is composed of an indigestible substance such as feathers, hide or hoofs. Sure, the protein level by analysis might be high (and even the experts don't agree as to just what amount qualifies as "high" protein level in a food) but if the dog's gastrointestinal tract is unable to break the protein molecules down into amino acids and then absorb and utilize those amino acids, the diet is worthless as a food source for the dog!

So "high protein" on the label means absolutely nothing; you've got to read the ingredients label to see if the source of protein is digestible.

See Table #1 to compare the approximate digestibility of the more common dog food ingredients. Egg white protein is used as the benchmark, giving it a value of one (1) since it is so highly digestible. Other protein sources are then compared to egg whites regarding their digestibility.

Table #1 - Protein Digestibility List

(Note: Values in table are approximate, as they have been taken from several nutrition sources and personal communications with nutrition experts.)

Egg whites 1.00
Muscle meats (chicken, beef, lamb) .92
Organ meats (kidney, liver, heart) .90
Milk, cheese .89
Fish .75
Soy .75
Rice .72
Oats .66
Yeast .63
Wheat .60
Corn .54

It's a good idea to explore the dog food label to see if the statement of its suitability is documented either by analysis or through feeding trials as specified by AAFCO (Association of American Feed Control Officials). You should have much greater confidence in the diet's nutritional value if feeding trials on live dogs have been done as opposed to the diet having been designed on paper only and, therefore, formulated by analysis.

Did you know that even if the dog food label says that the ingredients are X, Y, Z that there may not be any X or Y or Z in the food at all? How could this happen? The practice of substitution of one or more ingredients is a greater possibility if you buy that food from a small local mill or if the food is of a generic variety. Generally, the larger manufacturers have set ingredient parameters that don't vary. This is called a fixed formula.

On the other hand, some pet food producers will substitute ingredients and not change the label to truthfully reflect what you're buying. Price and availability of raw ingredients change from day to day, the less ethical producer will then substitute one ingredient for another in order to keep production costs to a minimum. They want to make that food as cheaply as possible! And changing the label to reflect the ingredient change is not required to be done immediately.

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