Understanding metabolizable energy (ME) is essential in determining the nutritional quality of your pet's food. Especially important when considering/comparing pet foods, ME is defined as the amount of energy available from pet food once the energy from feces, urine, and combustible gases has been subtracted. Essentially, ME is the energy left for your pet's body to use once all digestion is complete.
To live a healthy, happy life, your pet needs a certain number of calories per day. ME, as shown on pet food packages, shows the amount of calories the food will provide your pet. Look on the package for a statement of calorie content, expressed as "ME (kcal/kg) = a number" (3481, for example). You should also see a number of calories per cup or per can, depending on whether the food is dry or canned.
ME per cup essentially equals the usable calories and their concentration/density. A higher ME number indicates a higher concentration of calories, and a more energy-packed food. Think of the difference between a sports energy bar and a rice cake. The energy bar has a much higher ME, because it contains concentrated calories for energy. Similar to an energy bar, pet foods with higher ME numbers (such as Drs. Foster & Smith pet foods) allow your pet's body more concentrated calories for more energy. Plus, your pet's body will use more of the food, eliminate less as waste, and give you less waste to clean up. Pet foods with a higher ME can also save you money in the long run since you can feed less and still provide needed calories to fulfill your pet's nutritional needs.