Finding the best food is vital to your pet's health and longevity. But deciphering pet food labels can be confusing. Follow these steps to be able to understand pet food labels and be able to compare pet products with confidence.
Note that pet food labeling (in the U.S.) is regulated on a federal and state-by-state basis, with guidance from the Association of American Feed Control Officials (AAFCO). However, AAFCO provides only minimum requirements. Be alert to the fact that pet food producers often use terms that are undefined by the regulations to communicate more effectively with consumers and improve their product's image in the market. The AAFCO warns on their website that "it is not rare at all that labeling and marketing information is designed to appeal to the latest trend in marketing human products."
Locate the "Guaranteed Analysis" on the pet food label. See the example under Tips below. Note that the percentages given for protein, fat, and fiber are measurements of the food in its current state. However, because different pet foods have different levels of moisture, you can only logically compare pet foods on a dry matter basis.
Notice that moisture levels in pet foods can range from approx. 6% to as much as 80%. Canned food obviously contains more moisture than dry kibble. But it may not necessarily contain as much protein, for example. You can't tell which food contains the most protein, fat or fiber until you have converted both labels to a dry matter basis.
Determine the amount of dry matter first, by subtracting the percentage given for moisture from 100%. Using the example below, the moisture accounts for 10% of the pet food. Therefore, the dry matter content is (100% - 10% = ) 90% of the pet food.
Convert the protein, fat and fiber percentages to a dry matter basis by dividing the percentages given on the label by the amount of dry matter (from the previous step). In our example, the 26% protein on the label converts to 28% on a dry matter basis by dividing 26% by 90%. (Notice that in our example the dry matter calculation is only slightly different than the labeled percentage. This is because the moisture level was only 10% per the label. If the moisture level had been, say, 40%, then the dry matter content would have only been 60% and protein on a dry matter basis would have been calculated as (26% divided by 60% =) 43%.)
Compare the new protein level of 28% on a dry matter basis to other pet foods (once you've converted the other pet food labels in the same way). Do similar comparisons for fat and fiber after converting to a dry matter basis calculation.
Consider that percentages alone don't tell the whole story. You may have 28% protein on a dry matter basis, but what is the source of that protein? You can get protein from chicken beaks and feet that are NOT good sources of nutrition for your pet!
Look next at the list of ingredients. Pet foods must list ingredients in order of weight. Generally, the first five ingredients will make up the majority of the pet food product. Ideally, look for meat as one of the first ingredients on a pet food label. Grains, such as corn, corn meal, whole wheat, barley, rice are used to provide essential energy for the pet and appealing texture to the kibble. Even the AAFCO website admits that "Economics plays a part in any ingredient selection" and "protein is not simply protein. Ingredients providing protein have specific amino acids which may or may not match the amino acid profile required by a cat or a dog." Manufacturers routinely combine multiple protein sources to provide for all the amino acids required for a healthy life.
Be mindful that pet food manufacturers can manipulate this information (e.g. by breaking an ingredient down into components and then listing them individually so that you don't notice a easily recognized undesireable ingredient too near the top of the list).
Some pet owners search for pet foods that use human grade ingredients with no animal by-products and avoid pet foods that use artifical colors, flavors, sugars and chemical preservatives (notably BHA and BHT). However, animal by-products like liver and other internal organs are excellent sources of the amino acids and other nutrients that dogs and cats need. In addition, dry pet foods need preservatives to prevent spoilage and degradation of essential nutrients.
Here's an example of the guaranteed analysis section of a pet food label: