Original August 2002, Revised September 2009
How do you know that the dog or cat food you feed provides top performance? The answer is its level of digestibility. Simply stated, digestibility is the percentage of protein and other nutrients in a particular diet actually available to and utilized by the dog or cat. The palatability of a particular pet food is also important, because a dog or cat must readily eat the product to obtain the nutrition it provides.
Not all pet foods are alike when it comes to digestibility. Nor can the level of digestibility be determined by the presence or absence of diarrhea, vomiting, or finicky eating. Small, firm stools are not a measure of the digestibility of a pet food, although the physical nature of the diet may influence stool size.
As important as digestibility is to the nutritional merit of a diet, not all pet food companies conduct feeding studies to determine the digestibility of their pet food diets. In addition, digestibility information is often not available on a pet food package.
Pet food labels carry the statement "crude protein" because the minimum or maximum amount shown is based on laboratory analysis of the nitrogen content from which the protein content is estimated.
It does not indicate the percentage of protein actually utilized by the dog or cat. This can be determined only by animal feeding studies. In fact, a product with higher guarantee of protein on a pet food label may deliver less protein to the dog or cat.
Digestibility Among Pet Foods Differs
What accounts for the difference in digestibility among pet food products? Any one or a combination of the following factors influence digestibility:
Formula - a combination of ingredients, with each ingredient having a different nutritional composition. The digestibility of the product will vary as the ingredients vary.
Nutritional balance - the correct ratio of the nutrients in the diet to help ensure their efficient utilization by the dog or cat.
Ingredient quality - poor quality ingredients can adversely affect the digestibility of a pet food.
Processing - a formula of good quality ingredients can have its digestibility reduced by over-cooking or over-processing.
Conducting Feeding Studies
At the Purina Technology Center extensive feeding studies to determine digestibility are conducted as a new pet food is being developed or if major modifications are made in an existing pet food.
Dogs of different ages and breeds and cats of different ages participate in digestion feeding studies. They are cared for under the same conditions and are housed in special units to enable the collection of individual fecal samples.
Quality Assurance
A strict quality assurance program by the manufacturer helps ensure the ingredient quality and processing necessary for high digestibility. At all Purina pet food manufacturing plants, some 60 different quality checks are made every eight hours to ensure that the product is manufactured according to research-backed specifications.
Incoming ingredients are carefully checked for protein level, moisture content, physical condition and other factors which may influence nutrition or palatability. Heat-processed ingredients are examined to be certain they are not charred or burned which can adversely affect both their flavor and nutrient availability. Any ingredient not meeting specifications is rejected and returned to the manufacturer.
Your Best Assurance
The reputation of the pet food manufacturer is perhaps your best assurance that the pet food you buy has undergone extensive feeding studies. If you have questions about the digestibility of a particular product, contact the manufacturer.
Comparing Protein Percentage and Protein Digestibility
Let's make a simple comparison between the protein percentage and protein digestibility listed on the labels of Dog Food A and Dog Food B. To determine the grams of protein in each of these products that will actually be utilized by the pet, multiply the percentage of crude protein by the percentage of digestible protein.
Product A:
21% Crude Protein x 86% protein digestibility = 18.1 grams usable protein.
Product B:
23% Crude Protein x 76 percent protein digestibility = 17.5 grams usable protein.
Although the label on Product B indicates a higher percentage of crude protein in the diet, Product A actually delivers more digestible protein which is utilized by the pet.
