By Dr. Elizabeth Knabe, DVM

Wildwood Animal Hospital and Clinic LLC

Many pets will eat the same brand of commercial pet food day in and day out for their entire lives. If a commercial food has a different level of quality versus another brand, it might make a difference in the long-term health of a pet. As veterinarians, we are often asked to comment on the appropriateness of a food for a particular pet.

To make sense of pet food labels, we need to understand the concept of “dry matter basis” (DMB). By taking the water out of the food, we can compare the percentages of nutrients of foods that have different moisture levels.

Pet food labels are required by the Association of American Feed Control Officials (aafco.org) to provide a Guaranteed Analysis (GA) on all canned and dry pet foods. The GA must list the percentages of four categories of nutrients: Protein, Fat, Fiber, and Moisture. To compare these nutrients, we must first determine the moisture level of the food.

Most dry foods are 10 percent moisture and 90 percent actual ingredients. To convert the percentage of the nutrient to a DMB, divide the value listed of the nutrient (for example, 25 percent protein) by the value of the food that is dry matter (90 percent). The resulting value is 0.278 or 27.8 percent of protein on a dry matter basis.

Using this calculation, we can compare nutrient amounts between brands and types of food (wet vs. dry, etc.) but not the digestibility and usability of the protein used to make the food. The GA by itself, therefore, is not a means to fully evaluate pet food quality, but it is a necessary tool in making an informed decision on which food to feed your pet.

Your veterinarian can provide other resources that offer more information on food ingredients.

Wildwood Animal Hospital and Clinic LLC is located at 210 Airpark Road in Marshfield and online at wildwoodanimalhospital.net.