How to Compare Cat and Dog Foods

Comparing one brand of pet food to another can be difficult because the information on the label is stated in three different ways; as fed, dry matter and metabolizable energy (ME). 

AS FED:   In my experience, as fed is the most common method used by pet food manufacturers.  I think of as fed as how it comes out of the bag, can, box or foil.  As fed includes water and minerals which makes it impossible to compare dry food to canned food without further calculations to account for the moisture content. 

DRY MATTER:  The next most common method used is dry matter.  This is a little more helpful because it excludes water allowing for comparison between canned and dry.  Unfortunately, it does not account for fiber, ash and other components that cannot be metabolized into usable energy.    

METABOLIZABLE ENERGY:  ME is the nutrient content divided by calories (Kcals).  In my opinion, it is the most accurate because it removes water, fiber, ash and other components that don’t contribute to energy intake.  This is the measurement I use when I want to compare diets.  Unfortunately, most companies do not put this information on the product label.   

Here is example of why I rely on ME to compare diets.  A few weeks ago, I treated a dog for pancreatitis.  The clients wanted to know what caused this condition since they were already feeding what they thought was a low fat diet.  When I reviewed the product information, the percentage of fat based on dry matter was the same as the prescription diet I recommend.  When I called the company for the product information in ME’s, I learned the fat level was actually twice as high as the prescription product.  

When I compare diets, I always get the product information in ME’s.  Since few companies print this on the label, it usually involves a call to the manufacturer.  In my experience, the reputable food producers are happy to provide a detailed analysis of their product.  If they refuse, I would view that as a red flag.  Recently, I called a company to learn more about their product because the label only contained a guaranteed analysis that included minimum values for crude fat and protein, and maximum values for fiber and moisture.  Since my patient needed a low protein diet, I wanted to know the maximum protein their product would contain.  The company refused to provide any further information stating, “Our product varies from batch to batch therefore, we can only provide these maximums and minimums.”  I hung up and crossed this company’s food off my list because of their lack of quality control.


Published by kristennelsondvm

Dr. Kristen Nelson grew up on a farm in Watertown, Minn., where she developed a deep love for animals of all kinds. She received a Doctor of Veterinary Medicine degree from the University of Minnesota, College of Veterinary Medicine. Kris then completed a small-animal internship at the prestigious Animal Medical Center in New York City. In addition to writing and speaking, she cares for small and exotic animals in Scottsdale, Az. Dr. Nelson is widely quoted in the media. Her credits include Ladies’ Home Journal, USA TODAY, the Los Angeles Times and numerous radio and television interviews. Dr. Nelson has written two books, Coated With Fur: A Vet’s Life and Coated With Fur: A Blind Cat’s Love. Kris and her husband Steve share their home with rescued cats, birds and a dog.