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The Importance of Reporting Pet Food Digestibility

Posted by Jim Galovski on
The Importance of Reporting Pet Food Digestibility - NOBL Foods


This article first appeared on LinkedIn



Jill Cline succinctly summarized pet food digestibility and bioavailability in the following statement,

"A food’s digestibility is the collective proportion of all nutrients in a food that is available to the dog for absorption from the intestine into the bloodstream. Nutrient bioavailability is the proportion of the absorbed nutrients that are carried to target tissues and are available for use by the body. Because a highly digestible food provides a higher proportion of absorbed nutrients than a less digestible food, digestibility provides one measure of a food’s nutritional value and quality."

You would be hard pressed to find an expert in animal nutrition that says digestibility does NOT matter. Linda Case was emphatic in her 2014 nutrition book Dog Food Logic that pet food manufacturers need to provide digestibility information to consumers. The Association of American Feed Control Officials (AAFCO) does not allow digestibility claims to be on pet food labels and only has a recommended protocol for digestibility studies (defined by Method 1). Case went on to state, "If pet food manufacturers insist on telling us that their brands of food are expected to provide 'complete & balanced nutrition' throughout our dog's lives, then providing a few very simple measures of the quality of those foods is not too much to ask."

If a manufacturer's food contains all the necessary nutrients in a highly digestible form, why wouldn't they share that information?


While the ingredients in Fido's food are required by Regulatory, the way in which they are presented makes their inclusion on the panel useless (from a nutritional standpoint). The listing order by weight, the practice of ingredient splitting and the abundance of artificial and synthetic ingredients ("No More Nasties" right Petco?) make it a guessing game as to what is actually in the food (inclusion rates) and why. I've given my thoughts in a previous article but sadly the industry is no closer to making any changes. The Guaranteed Analysis - What EXACTLY is this telling you because it is not an accurate reflection of the nutrient content. Crude Protein (CP)? Most folks would be surprised to know that Crude Protein is called “crude” because the assay used in its determination doesn't actually measure protein at all. Instead, the analysis used by most laboratories measures nitrogen. The "protein" value is calculated by multiplying the nitrogen result by 6.25. Remember the 2007 melamine recall? The melamine was added to increase nitrogen, thereby giving an inflated Crude Protein result. When we talk about "quality" of proteins, we aren't talking about whether the beef used is marbled and classified as USDA Prime or Choice, we are talking about the essential amino acid content. From a consumer protection perspective, AAFCO and the FDA should require pet food manufacturers to supply the amino acid profile of their diets. Imagine a consumer thinking that more protein is better so they quickly jump to a diet, with a premium price, that claims 44% CP. The consumer has intentionally been misled. First, CP is measuring nitrogen and secondly, the consumer has no idea of the "quality" of the protein.

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Now if manufacturers shared a few simple data points (e.g. their amino acid profiles), a consumer could determine (by adding the Essential Amino Acids together and subtracting from Crude Protein) that the 44% CP gets 16.8% from the essential amino acids and 27.2% comes from non-essential. Compared to the manufacturer with 35% CP which gets 27.2% from essential amino acids, and only 7.8% from the non-essential amino acids. Remember, a dog doesn't require non-essential amino acids because they can synthesize them internally. Any excesses are removed from the body and provide no benefit to the dog. The chart below shows 5 different product forms (freeze-dried, "fresh", dehydrated, vegetarian and meat based kibble) and their essential and non-essential amino acid test results.

Essential and NonEssential Amino Acid Composition of Crude Protein on GA

HOW IS DIGESTIBILITY MEASURED AND REPORTED? - The most common and accepted practice in the industry to determine digestibility is through feeding (Method 1 of AAFCO). Healthy dogs are fed a pre-weighed amount of food for maintenance (e.g. 300 grams/day). There is a feeding acclimation period so that the dogs can adjust to the food and "empty" their bowels of previously eaten food. After that acclimation, fecal matter is collected, analyzed and weighed. In our example, 300 grams of food is presented, 280 grams consumed and 55 grams of fecal matter is collected (280-55 = 225 or 80.3% digestible). Digestibility is then broken down further into Dry Matter, Protein, Fat and Caloric Digestibility. Additional information collected is the acceptance of the food over the test by the dog (consumed/presented) along with fecal consistency and frequency. The standard 5 point fecal scoring system is used (1 = watery diarrhea and 5 = dry, hard, crumbly with 0 = no fecal matter). NONE of these tests are invasive or infringe/interfere with the dog's well being. My argument is that NOT performing these tests and operating blindly is MORE harmful to the dog!

Guardian MoRE Canine Food Bar - Beef & Chicken Recipe Digestibility Results

The average digestibility percentages (estimated) for dry kibble in protein, fat and dry matter are 81%, 85% and 79%, respectively. We already worked the math to show that the 44% CP diet is actually only delivering 16.8% essential amino acids. At 81% digestibility, this number drops to 13.6% being absorbed by the body and available!! It doesn't make any sense to allow consumers to think they are getting 44% protein when they are actually only getting 1/3 of that number from the essential amino acids.

Maybe this real-life example is why getting a manufacturer to provide digestibility numbers is like pulling teeth! I reached out to 14 manufacturers and only 2 provided their digestibility results (Primal shared their digestibility results (a solid 89.1% on protein) and Purina would only provide their veterinary numbers which ranged from low 60% to nearly 90%). Of the 12 manufacturers that would not supply their digestibility information, here are their responses:

  • Hi again, Jim! At Nulo, we do not conduct formal digestibility studies, as we are animal lovers at our core and take great care to provide safe, premium food products without invasive testing of any kind.
  • Hi there! Thank you so much for your interest in Pet Plate! We are still a very young company so we haven't done all of the testings that a long time company has done. We will be conducting more tests on our meals this year and we will have that information readily available for customers as soon as we get the results from the product team. They are currently conducting a vitamin analysis and they plan to do an amino acid evaluation and a digestibility test in the next couple of months. 
  • Hi Jim, Thanks for reaching out to [Solid Gold]. While we unfortunately do not share our digestibility results I would be more than happy to help you with any other information you would like. Have a wonderful day!
  • As an ethical vegan company, we [V-Dog] do not conduct any laboratory testing, including digestibility trials. We're currently working on a volunteer-based study with Ross University and will be releasing data later this year.
  • Good morning Jim, Thank you for reaching out to Fromm Family Foods. Unfortunately, we do not have a full amino acid profile or digestibility report that will be presented to the public.
  • Royal Canin is unique in that we do digestibility trials on our products prior to releasing them to the market. We don’t however report the digestibility numbers to the public.  
  • We [Stella and Chewys] do not feel that feeding trials are the best way to ensure that our products are complete. I always suggest people look at the requirements and allowances for the feeding trials - they really are not the most scientific way to determine the health of a food. We formulate the dinners to meet the guidelines, and then sporadically test them through a 3rd party lab to ensure that they’re meeting all requirements.
  • We [Wynwood Dog Food] do not do digestibility trials but rely on Dr. Shmalberg's expertise.
  • We feel our 40 years of experience feeding hundreds of thousands of animals through multiple generations, with some pets living into the unheard of late twenties, is the more compelling proof of the merits of Dr. Wysong's pet feeding philosophy.
  • Hi Jim, Thanks for your email. We do not have digestibility numbers for this specific recipe. Since our Endless Valley recipe is a certified vegan recipe, we are not permitted to use animals in any part of the testing process including digestibility. 
  • Does Halo perform digestibility (NOT feeding) trials? Yes - however we do not share the information.
  • Does Addiction share their AAFCO amino acid profile/analysis? This is proprietary information we do not share with the public. * Does Addiction perform digestibility trials? No. 

The responses run from a simple, declamatory "No" to a treatise on how there is no such thing as "complete and balanced" so therefore no testing is needed. If you DO NOT test your diets, you have no idea if the mathematical assumptions made during formulation actually play out and are beneficial to the dog!! If you DO test your food, why are you not sharing the results? There is not one thing that can be learned about your formula or processes by sharing your digestibility numbers. And as for the data being proprietary or confidential, anyone can test digestibility and the amino acid profiles if they pay the lab fees. I'll have more on this and share actual test results in a future post! While most animal welfare organizations are opposed to long term feeding trials because of the PETA videos from the Iams facilities almost 2 decades ago, digestibility tests are about 2 weeks long and non-invasive.

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WHAT AFFECTS DIGESTIBILITY? - So how is it that two diets with similar ingredients and GAs can have different digestibility results? Things like formulation, ingredient quality and processing are the biggest factors that a manufacturer controls. While the extrusion process improves digestibility of starches and carbohydrates, it is no secret that it reduces protein quality due to the Maillard reaction, decrease in palatability and loss of heat-labile vitamins. Vitamin A for example can see a loss of up to 65% of its nutritional value after extrusion. This is why the typical dry kibble ingredient deck contains 25+ artificial and synthetic "stunt doubles" (not the "real" ingredient but one that is substituted in to survive the heat, pressure and physical alterations associated with extrusion). Some ingredients, when combined, will reduce overall digestibility and bioavailability by blocking the dogs ability to synthesize and/or transport nutrients. If you don't test digestibility, you won't see or understand these nuances and how it affects your dog!

The most important thing when it comes to selecting a pet food for your dog is making sure they are "Not just surviving but thriving"(tm). The vast majority of us are NOT Certified Professional Animal Scientist, Board Certified or a Fellow of the American College of Nutrition so we need manufacturers to tell us what they are offering (from a nutrient perspective) in our pet's food. The argument that it is too complex to explain or that consumers "won't understand" is just lazy and insulting to our customers and consumers.

FOOD FOR THOUGHT - As consumers, we MUST start demanding answers from pet food manufacturers on digestibility, amino acids and nutritional quality. The more we ask and the more insistent we are on implementing changes, the sooner the industry will have to respond. Our pets will thank us!

When selecting a food for digestibility, if the manufacturer does not provide the information you need, here are some directional guidelines to help you "guesstimate" digestibility:

  • Highly digestible foods produce well formed and firm feces, at regular intervals. It should not contain blood, mucous or any recognizable part of the food itself. Of course you need to feed different foods for comparison
  • Your pet should have less frequent defecations and should NOT have excessive flatulence, diarrhea or loose stools
  • Your dog should readily and happily consume the food. There should be no need to entice your pet with treats, toppers, table scraps or other human foods
  • When comparing foods, look at the recommended feeding amount for your dog's weight (not just cups, make the conversion to grams using the step by step below). If one requires significantly more grams, most likely that diet is the one with lower digestibility.

SUMMARY - If you are a consumer, demand facts and actual science from your pet food company. Once you have the data, do research on what it really means to you and your pet. If your current pet food isn't part of the answer, they may be part of the problem! If you are a manufacturer, MAKE YOUR DATA AVAILABLE. Whether it is online or through your customer service department, transparency, science and education is key! For the Regulatory organizations overseeing pet food, maybe it is time to treat the industry as FOOD and NOT FEED. Change the labeling requirements; require more than MINIMAL STANDARDS and put the need's of pets first!

"The truth is always stronger in the end if people stand up and fight for it."


GRAMS/CUP MATH - Take the kcal/kg number and divide by 1,000. This gives you kcal/g (3,714/1000=3.714). Take the kcal/cup and divide by the kcal/g (421/3.714=113.4g). We now know this food weighs 113.4 grams per cup. The manufacturers daily feeding requirement for a 25lb dog is 1.75 cups (1.75x113.4=198.5 grams/day). Compare that to a food that only requires 56.7 grams daily for a 25lb dog.

CRUDE FAT MATH - Same two diets. The first one reports 16% Crude Fat. Multiply the 198.5 grams by 16% and you get 31.75 grams of Fat/day. The second diet reports 31% Crude Fat. Multiplying the 56.7 grams by 31% you get 17.6 grams of Fat/day. You wouldn't think the 31% Crude Fat diet delivers 45% LESS FAT than the 16% Crude Fat diet, daily.

DAILY FEEDING COST MATH - So the first diet comes in a 4lb bag (1.814kg) and sells online for $15.58. Based on our grams/cup math and daily feeding requirement, we know (1,814g/198.5g=9.1 days) so its easy to figure out that the daily feeding cost is $1.71 for a 25lb dog ($15.58/9.1=$1.71)

My co-founder and I founded Guardian Pet Food with a very simple, straight forward mission statement: "Pets Before Profits." Everything we do starts with the health and well being of the pet. If you have any questions, please don't hesitate to ask!

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