Dog Food Digestibility Study: Six JustFoodForDogs Recipes Tested
A University of Illinois study measured the true nutrient and amino acid digestibility of six JustFoodForDogs recipes using the cecectomized rooster assay — a precision method that removes the variability of gut fermentation entirely.
PUBLISHED IN TRANSLATIONAL ANIMAL SCIENCE
JFFD RECIPES TESTED
UNIVERSITY OF ILLINOIS AT URBANA-CHAMPAIGN
AMINO ACIDS MEASURED
THE RESEARCH
Peer-reviewed research measured true nutrient and amino acid digestibility across six JFFD recipes.
In 2020, researchers from the Department of Animal Sciences at the University of Illinois at Urbana-Champaign published a study measuring the true nutrient and amino acid digestibility of six JustFoodForDogs recipes.
Rather than the standard fecal-based (apparent) digestibility method, researchers used the precision-fed cecectomized rooster assay — a gold-standard technique that removes the confounding effects of hindgut microbial fermentation, producing a more precise picture of true nutrient and amino acid absorption.
The study was published in Translational Animal Science, a peer-reviewed journal of the American Society of Animal Science.
PEER-REVIEWED · OPEN ACCESS
Translational Animal Science · Vol. 4(1) · January 2020
True nutrient and amino acid digestibility of dog foods made with human-grade ingredients using the precision-fed cecectomized rooster assay
Authors: Oba PM, Utterback PL, Parsons CM, Swanson KS
University of Illinois at Urbana-Champaign
A precision-fed rooster assay measuring true nutrient and standardized amino acid digestibility, along with nitrogen-corrected true metabolizable energy (TMEn), across six human-grade dog food recipes.
RECIPES TESTED
SIX CORE JFFD RECIPES STUDIED
Unlike many digestibility studies, which test one or two products, this research covered the full JustFoodForDogs recipe lineup available at the time.
Beef & Russet Potato
Chicken & Rice
Fish & Sweet Potato
Venison & Squash
Turkey & Whole Wheat Macaroni
Lamb & Brown Rice
KEY FINDINGS
What the study found
These are the researchers’ published conclusions.
85% +
INDISPENSABLE AA DIGESTIBILITY
Oba et al., Transl Anim Sci, 2020
6/6
RECIPES PERFORMED WELL
Oba et al., Transl Anim Sci, 2020
↑ TMEn
ENERGY VALUES UNDERESTIMATED
Oba et al., Transl Anim Sci, 2020
STUDY DESIGN
What sets this method apart
Most digestibility studies measure what comes out in stool. This one measured something more precise.
THE METHOD
The Cecectomized Rooster Assay
Researchers surgically removed the ceca (a hindgut fermentation organ) from roosters used in testing. Because fermentation by gut microbiota can distort digestibility measurements, removing this variable allows researchers to measure true nutrient and amino acid digestibility — closer to what is actually absorbed by the body, independent of microbial activity in the lower gut.
WHY IT MATTERS
True vs. Apparent Digestibility
“Apparent” digestibility (measured via stool, as in fecal-based studies) can be influenced by gut bacteria breaking down nutrients after they’ve already passed the point of absorption. “True” digestibility, measured via this precision method, gives a more accurate picture of how much protein and amino acid content is actually available to the animal.
PUBLISHED DATA
True nutrient digestibility by recipe
Selected results from Table 1 of the published study, shown as percentages of dry matter, organic matter, fat, and gross energy digested.
RECIPE
Beef & Russet Potato
Chicken & Rice
Fish & Sweet Potato
Lamb & Brown Rice
Turkey & Macaroni
Venison & Squash
DRY MATTER
74.0%
82.3%
67.2%
81.0%
78.0%
67.6%
ORGANIC MATTER
81.9%
89.2%
76.4%
87.3%
81.9%
74.1%
FAT (AHF)
87.9%
94.6%
92.7%
85.0%
93.1%
93.1%
GROSS ENERGY
86.9%
93.7%
83.8%
89.1%
86.6%
82.3%
Source: Oba PM, Utterback PL, Parsons CM, Swanson KS. Table 1, Transl Anim Sci. 2020;4(1):442–451. Values represent true digestibility as measured via the precision-fed cecectomized rooster assay (n = 4 roosters per treatment). Statistical comparisons and significance values are available in the full published study.
"Although statistical differences were observed among foods tested in this study, all foods performed very well. All foods tested had very high AA digestibilities, with most exceeding 85% and some over 90%."
COMMON QUESTIONS
Questions pet parents ask about this study and what it means.
What is the cecectomized rooster assay, in plain terms?
It’s a precision-feeding method used in animal nutrition research where roosters that have had a portion of their digestive tract (the ceca) surgically removed are fed a known amount of food, and researchers measure exactly what comes out. Because the ceca is where gut bacteria ferment leftover nutrients, removing it means the results aren’t skewed by microbial activity — giving a cleaner measurement of true digestibility. It is a long-established and widely used method in poultry and companion animal nutrition research.
How to "true" digestibility different from "apparent" digestibility?
Apparent digestibility (often measured through fecal sampling) reflects the difference between what’s eaten and what’s excreted, but it can be affected by gut bacteria that ferment and alter nutrients in the lower intestine. True digestibility, as measured in this study via the cecectomized rooster assay, removes that variable, offering a more precise estimate of how much of a nutrient is actually absorbed by the body before reaching the hindgut.
Which JustFoodForDogs recipes were tested?
All six recipes available at the time of the study were tested: Beef & Russet Potato, Chicken & White Rice, Fish & Sweet Potato, Lamb & Brown Rice, Turkey & Whole Wheat Macaroni, and Venison & Squash.
What does amino acid digestibility tell you about protein quality?
Amino acids are the building blocks of protein, and their digestibility is one of the most direct ways to assess protein quality in a food. High amino acid digestibility means a greater proportion of the protein a dog eats is actually broken down and absorbed for use in the body, rather than passing through undigested. Researchers consider amino acid digestibility data more nutritionally meaningful than total protein content alone, because it reflects what’s bioavailable, not just what’s present in the formula.
Was this study funded by JustFoodForDogs?
Yes. As disclosed directly in the published study’s funding statement, this research was funded by JustFoodForDogs LLC. The study design, data collection, laboratory analysis, and conclusions were conducted independently by University of Illinois faculty and published in a peer-reviewed academic journal. We disclose this funding relationship transparently, consistent with standard academic practice. Funded research that is peer-reviewed and published is common and accepted in nutrition science.
CITATION
Oba PM, Utterback PL, Parsons CM, Swanson KS. True nutrient and amino acid digestibility of dog foods made with human-grade ingredients using the precision-fed cecectomized rooster assay. Transl Anim Sci. 2020 Jan;4(1):442–451. doi: 10.1093/tas/txz175.
Funding disclosure: This study was funded by JustFoodForDogs LLC, as disclosed in the original publication. The research design, data collection, and analysis were conducted independently by University of Illinois faculty. We report this funding relationship transparently, consistent with standard academic disclosure practices.
Content disclosure: This content is educational only. Consult your veterinarian for guidance specific to your dog’s health needs.