Comparing Pet Foods

Once you have an idea about your pet’s daily needs and know how to read pet food labels, you can use this knowledge to compare the suitability of different diets for your pet from our diet tables or other sources. 

Pet food comes in three physical forms: dry, semi‑moist, and canned.  Each form represents a standard method of food preservation, and each has advantages and disadvantages.  Moreover, the nutritional quality of the food does not depend on its physical form; good and bad examples of all forms can be produced.  The nutrient content of diets can be compared in three different ways:

  1. As Fed- For diets of similar moisture and calorie content, one can use the amount of nutrient per unit as fed - AAFCO regulations require that the information in the guaranteed analysis described above be reported this way, making for easy comparison when appropriate.
  2. Dry Matter Basis-For diets of differing moisture (e.g., dry vs. canned), but similar calorie content, one can use the amount of nutrient per unit dry matter
  3. Per 100 kilocalories- For diets of differing Calorie content (e.g., high vs. low fat), compare foods using the amount of nutrient per 100 kcal. 

Making direct comparisons of nutrient content on an as fed basis can be quite misleading because of the different amounts of water and energy in pet foods.  For example, the amount of protein guaranteed on the label of dry cat foods is about 35%, and in canned foods about 10%.  Canned foods, however, contain more water than dry foods do.  For products of differing moisture content but similar energy density, a more appropriate way to compare the nutrient content is on a "dry matter" basis.

Comparing Pet Foods - Dry Matter Basis

Comparing food on a dry matter basis takes differences in water content out of the equation so nutrients are compared on a common basis.  One common misconception is that foods that use fresh meat such as beef, chicken or turkey have more protein in them than foods that use protein meals, because fresh meat is listed first on the ingredient list, whereas meat meals may not be.  Fresh meat is ~ 75% water, however, whereas protein meals are essentially dry.  If you removed the water from a food that was made with fresh meat and also from one that was made using a protein meal, you might find the foods contain very similar amounts of protein, or even that the food with the meal contains more protein.  To compare foods based on their dry matter content, use the following steps:

  1. Subtract the moisture content listed on the label from 100 to find the % Dry Matter (% DM).
  2. Divide the individual nutrients by the % DM 

Example:

Food 1 - 100% - 10% moisture = 90% DM

Food 2 - 100% - 76% moisture = 24% DM

16% protein/90%DM = 17.8% protein DMB for Food 1

15% protein/24% DM = 62.5% protein on DMB for Food 2

Now we can see that when moisture is removed, Food 2 actually contains much more protein.

 

Example Food Labels

Food Label Example 1       Food Label Example 2

 

Comparing Pet Foods – Calorie Basis

Because of the wide variation in water and energy content of pet foods, we prefer to compare foods on the basis of amount of nutrient per 100 kilocalorie of food, and we present nutrient content this way in the diet tables here on our website.  The information included in our diet tables includes protein, fat, fiber, and when available carbohydrate, calcium, phosphorus, and sodium, content as well as the Calorie (in kilocalories) content per measuring cup (dry foods) or can, the price range, the cost per 100 Calories of diet, and special categories.  These values simplify diet comparisons because the information is all provided on a standard basis (amount per 100 kilocalories).  The values are only as accurate as the information provided by manufacturers however, and are provided to help people choose foods that best meet their pet’s needs.

We list nutrients on an amount per 100 calorie basis because of the wide variation in the fat content of commercial diets.  Because some companies tout the presence of "high" or "low" nutrient densities in pet foods, we offer the provisional definitions below as a frame of reference:

Nutrient

Dog

Cat

Low calorie

< 3 kcal/gm dry matter

High calorie

>4.5 kcal/gm dry matter

Low protein

<5 gm/100 kcal

<7 gm/100 kcal

High protein

>8 gm/100 kcal

>10 gm/100 kcal

Low fat

<2 gm/100 kcal

High fat

>5 gm/100 kcal

Low fiber

<0.25 gm/100 kcal

High fiber

>1.5 gm/100 kcal

Low sodium

<100 mg/100 kcal

Vitamin-Mineral and other Supplements

Vitamin-mineral and other food supplements for your pets are growing markets; the shelf space dedicated to these products at local pet stores seems to increase all the time.  However, here is what all pet owners should know: all foods that meet AAFCO standards already include the essential and required vitamins and minerals that normal healthy pets need, so you don’t need to supplement your pet’s diet unless a condition or disease necessitates it, or if a diet not meeting AAFCO standards (like a homemade diet) is being fed.  Some vitamins, minerals and additives even can be harmful in excess, which is even more reason to be wary and to consult a veterinarian or veterinary nutritionist before adding anything to your pet’s diet.  That said, many pet food companies now add moderate levels of substances not recognized by AAFCO as “essential” that are thought to be or have been proven to be in some respect beneficial such as:

  • Glucosamine and Chondroitin –believed by some to be beneficial for “joint health”, although scientific evidence suggests that they are of little, if any, value for most pets.
  • Eicosapentaenoic Acid (EPA) and Docosahexaenoic Acid (DHA) – these polyunsaturated fatty acids have been shown to be of benefit for osteoarthritis. Recommended for anti-inflammatory benefits in many chronic diseases (heart, kidney, cancer)
  • Ascorbic Acid (Vitamin C) – dogs and cats both make plenty of ascorbic acid in their liver, and there is no need for (or benefit from) giving vitamin C to pets. 
  • L-Carnitine – involved in cardiac and skeletal muscle function and health, carnitine may be a “conditionally essential” nutrient for some animals.  
If you are interested or concerned about including nutrients above the amounts recommended by AAFCO, some experts recommend providing them in food rather than adding them separately to prevent over supplementation and ensure quality of the additive; most pet food companies test and quality check their foods for concentration and have secure sources for their additives. We recommend consultation with a veterinary nutritionist before supplementing your pet’s diet.