Pet Nutrition
                     Pet Food Labels: Part One

                        By Wendy C. Brooks, DVM, DipABVP
Educational Director,

All it takes is a visit to the pet supply store to be bombarded with pet food recommendations.
Some foods are touted to have special properties rendering them superior while other foods
are frowned upon. Frequently visiting a different store leads to a total reversal of
recommendations. Nutritional hype is everywhere.

The List of Ingredients

Everyone is familiar with a list of ingredients. We see these lists on the foods that we consume.
Pet foods also have a list of ingredients with the most predominant components listed first
according to their weight.

Each term on this list is specifically defined by the AAFCO (Association of American Feed
Control Officials) and a catalog of definitions is available for all the terms that may be used on
this list. One might think something like chicken does not really require a definition but, in fact,
the AAFCO finds that it does.

CHICKEN: the clean combination of flesh and skin with or without accompanying bone, derived
from the parts or whole carcasses of chicken or a combination thereof, exclusive of feathers,
heads, feet and entrails.

Beef is similarly strictly defined.

BEEF: the clean flesh derived from slaughtered cattle, and is limited to that part of the striate
muscle which is skeletal or that which is found in the tongue, in the diaphragm, in the heart, or
in the esophagus; with or without the accompanying and overlying fat and the portions of the
skin, sinew, nerve and blood vessels which normally accompany the flesh.

This may seem bizarrely graphic but it is important to differentiate the main flesh of the meat
source from the by-products (which are generally the organ meats) or meat meal (which is
basically ground up meat) or meat digest (meat that has been treated with enyzmes).

There has been an assortment of rumors regarding meat by products that suggest that these
include hair, feathers, hooves or other poorly digestible tissues.
It should be noted that these
tissues are specifically excluded from the definition of by products by the AAFCO.

Another source of confusion in the ingredient list is the fact that the vitamins that fortify the pet
food are listed by their biochemical names. This tends to make the list read like some sort of
chemical textbook. Here is a handy guide for those unfamiliar with common supplements:

Ferrous sulfate:    an iron supplement

Thiamin:    more commonly known as vitamin B1

Niacin:    more commonly known as vitamin B3

Alpha Tocopherol:   more commonly known as vitamin E

Calcium Pantothenate:    Also called coenzyme A, an important metabolic cofactor

Pyridoxine Hydrochloride:    more commonly known as vitamin B6

Riboflavin:    more commonly known as vitamin B2

A more complicated issue would be what to look for on an ingredient list. Some labels flaunt
such statements as “no soy” or “no corn” or “no preservatives” or “no by-products.” Some make
a point of having meat as first ingredients while others have grains as first ingredients. Why are
these issues marketing points?

The Pet Food Label

A wealth of information is available on the pet food label but it is practically in secret code to
those who do not know what they are reading. All marketed foods must have a guaranteed

Here are two samples:

Skippy Premium Canned Food   Guaranteed Analysis (from label)
Crude Protein: Min 8.0%
Crude Fat: Min 2.0%
Crude Fiber: Min 1.5%
Moisture: Min 82%

Hill’s Canine R/D (20 pound bag) Guaranteed Analysis (from label)
Crude Protein: Min. 20%
Crude Fat: Min  5.5%
Crude Fat: Max  9.0%
Crude Fiber: Max: 26%
Moisture: Max. 11%  Min
Calcium: Min.  0.5%
Phosphorous: Min. 0.35%
Carnitine: Min. 200 ppm

Why Don’t These Numbers Add Up to 100%?

What you are supposed to know but probably didn't know is that carbohydrate content is the
missing component. One hundred percent minus the sum of the factors listed is understood to
be the carbohydrate content.

Which Food Has More Protein?
It would seem natural to simply read the labels pictured above: the Skippy brand is minimum
8% protein and the Hill’s R/D is minimum 20% protein. Obviously the R/D has more protein,

Not so fast.

To compare foods, one has to remember that food consists of water plus the actual nutrients.
The water itself does not have any protein. To compare the protein content of two different foods,
then, the water factor must be removed before you can accurately compare; that is, the foods
must be compared on a dry matter basis only.

For example:

The Skippy above is 82% water and the can’s net weight is 624 grams. Since 82% of that 624
grams is water, that means that the remaining 18%, 112 grams, is the food. The dry matter is
18% of the total can.

The R/D is 11% water, and the bag weighs 9 kg. That means that the remaining 89% of the bag,
or 8 kg, is food. Of the total 9 kg bag, 1 kg is water and 8 kg is food.

The reason we need to figure out what percentage of the food is water and what percentage is
dry matter is because the percentage of protein listed in the guaranteed analysis on the label is
said to be “as fed” rather than on a dry matter basis. But since the water content doesn’t contain
any protein, to compare the amount of true protein the pet is receiving from the food, we have to
divide the “as fed” percentage of crude protein (from the guaranteed analysis label) by the
percentage of dry matter.

The Skippy (above) true protein content =  8/18 = 44%

The R/D (above) true protein content   =  20/89 = 22%

It is the Skippy food in this example that has substantially higher protein content.

The Moral of This Story

The guaranteed analysis has a tremendous amount of information but it is important to know
what the analysis is telling you. Foods cannot truly be compared based on the “as fed” numbers
on the label.

Instead of relying on the clerk at the pet food store or from advertisements to decide what food is
best suited for your pet, learn the facts about nutrition to help you separate the facts from the

See Pet Food labels:Part Two

Date Published: 1/1/2001  
Reprinted from
Copyright 2001 - 2004 by the Veterinary Information Network, Inc. All rights reserved.
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