The most important thing to evaluate on a pet food label is the nutritional adequacy statement. This gives you information about whether the pet food is complete and balanced, meaning all essential nutrients are present in the proper amounts and proportions, without nutritional excesses or deficiencies.
The nutritional adequacy statement or “AAFCO statement” is required on the label of every pet food. The nutritional adequacy statement tells you several things, including if the product is complete and balanced, who the product is complete and balanced for (dog or cat), what life stage the product is complete and balanced for (growth, reproduction, adult maintenance, or all life stages), and how the product was determined to be complete and balanced (formulated to meet AAFCO nutrient profiles or animal feeding tests). If the product is not complete and balanced, the nutritional adequacy statement will say “intended for intermittent or supplemental feeding only.” Pets without health issues should not be fed a diet that says “intended for intermittent or supplemental feeding only” in the nutritional adequacy statement, especially not long-term. Sometimes, veterinary therapeutic diets have that designation in the nutritional adequacy statement, and that may be a result of needing to restrict certain nutrients for pets with chronic health conditions. For example, protein is often restricted for patients with kidney or liver disease and may be lower than what AAFCO recommends for a healthy pet. As a result, some of the diets for dogs and cats with kidney or liver disease may not be complete and balanced overall, but they do contain adequate levels of nutrients that do not need to be restricted for health. Your best resource for questions about the nutritional adequacy statement or pet food in general is your primary veterinarian or a board-certified veterinary nutritionist.
The ingredient list was never intended to be a tool by which to “evaluate” a pet food. Pet food ingredients have an agreed upon definition set by the Association of American Feed Control Officials (AAFCO). The ingredient list is a statement declaring the contents of the product, and the manufacturer must abide by the definition of each ingredient, e.g., the product cannot contain poultry if not listed and the product must contain taurine if it is listed. Every ingredient added must be on the list. The ingredient list was not intended to state or imply the nutritional quality of the final product for a dog or cat and cannot be accurately used for that purpose.
The ingredient list is listed in decreasing order by weight. The goal is to have a complete and balanced pet food that is palatable and supports the health of the pet. Not every essential nutrient is required in the same quantity in the pet food. There are nutrients that are required in larger amounts (such as fiber, protein, and fat) and there are nutrients that are required in smaller amounts (vitamins and minerals, for example). As a result, it’s not possible to rate a pet food based on the nutrients that come first. The pet food is the sum of its parts (ingredients), but those parts are not intended to be included in equal amounts. The weight of ingredients and order in the ingredient list is based on their water content, and water can be heavy. As a result, the order of ingredients can account for their water content and not as much their nutrient contributions.
The WSAVA nutrition toolkit (https://wsava.org/Global-Guidelines/Global-Nutrition-Guidelines/) is a resource for veterinarians and pet owners alike. For pet owners wanting to learn more about selecting a healthful pet food for their pet, there is guidance on selecting a pet food (https://wsava.org/wp-content/uploads/2021/04/Selecting-a-pet-food-for-your-pet-updated-2021_WSAVA-Global-Nutrition-Toolkit.pdf) and other owner resources. Important things pet owners can do is to look at the nutritional adequacy statement on their pet’s food to ensure that it is complete and balanced. Another thing pet owners can do is keep treats and other unbalanced “extras” in their pet’s diet to no more than 10% of total daily calories. Because treats and other extras are not usually complete and balanced, feeding too many treats can actually unbalance the diet. This can result in nutrient deficiencies or excesses from the overall nutritional plan being unbalanced as a whole.