Finding the best food for pets has become a frustrating and time consuming process. With isles full of foods, people read the labels thinking that will help them identify the best one. They mistakenly think that dog and cat food can be compared by the Guaranteed Analysis (GA). Nothing could be further from the truth! Metabolizable Energy (ME) should be used instead.
The guaranteed analysis is simply a list of the percentage of fat, protein, fiber and moisture in the food. Specifically, the list includes the minimum crude protein, minimum crude fat, maximum crude fiber and maximum moisture. The term ‘crude’ means all the nutrients are included in the results whether they can be digested or not. For example, a label can say 25% minimum crude protein even though only half of it is digestible. The actual amount of useful protein is 12.5%. The opposite happens with crude fat because this value is listed as a minimum. The value on the guaranteed analysis is much lower than what is actually digested because many pet food companies add highly digestible fat to make it taste better. In my opinion, the term guaranteed analysis is more confusing than helpful. I would like to see it removed from labels and replaced by metabolizable energy.
Metabolizable Energy is a much better method for comparing diets because it only reports what is actually digested. The USDA defines it as follows: “The net energy in food or feed that is available to humans or animals by digestion and absorption, and measured as the difference between gross energy and the energy lost as being digested or indigestible.” That means that the energy lost in digesting the food through the urine, feces and combustible gases is not included. Metabolizable energy takes into account the quality of the ingredients which allows for an ‘apple to apple’ comparison. Guaranteed analysis does not.
Several years ago, I treated a miniature schnauzer for pancreatitis. This breed is prone to pancreatitis because they often have too much fat in their bloodstream. After treatment, I sent the dog home on a low fat (8% ME fat) canned diet. Three months later, the dog came back with pancreatitis again because the owner didn’t like the food I recommended. She went to a specialty pet food boutique and selected a food that was 8% minimum fat based on the guaranteed analysis. When I converted the guaranteed analysis of the food she bought to metabolizable energy, the food was actually 52% fat! The dog almost died because of the confusion caused the the label.
Guaranteed analysis results can be converted to metabolizable but the calculations are time consuming. Instead of doing it yourself, I recommend using the converter provided by BalanceIt.com. The nutrition service at the University of California-Davis, College of Veterinary Medicine created this helpful tool. Simply plug in the numbers from the guaranteed analysis listed on the label and the converter will do the rest.