Obligate carnivores are not obligated to eat meat - Study shows high Digestibility of plant ingredients in Cats


A commercial pet food supplier, ADM Animal Nutrition, recently published a report recognizing validity of plant ingredients in cat food and advising their inclusion in cat food formulations.

That's great news, but let's pause for a second.

A commercial pet food supplier advocating for plant-based ingredients? Well, that's rather odd.

Most pet food suppliers supply meat-based products and advocate the inclusion of meat-based constituents. Their objective is usually to make the optimal food for cats, with high palatability, not necessarily the most ethical food.

That is why it's unusual to have a pet food ingredient supplier advocating plant-based ingredients and backing up their claims with research.

So what does ADM say in their report? 

ADM Animal Nutrition Report

In their report ADM says(4):

The recently published research demonstrates plant- and yeast-based protein sources are nutritious alternatives that can be used effectively by adult cats.

They are referring to 2 research studies. One of them states "Plant proteins improve digestibility of a diet in cats(1) and the other study says "Plant proteins provide high-quality amino-acids to cats(2,3)

ADM continues(4):

This research separates fact from fiction by showing cats are not obligated to meat and other animal-derived ingredients only.

Recognition of plant ingredients and their inclusion in the cat food by a commercial pet food company helps remove a stigma surrounding plant-based cat diet. It shows that plant ingredients are sources of nutrients (proteins, amino-acids, vitamins, etc.), the same way as meat and fish are.

ADM Animal Nutrition references two research studies that prove the protein digestibility of plant ingredients for cats, and bio-availability of amino acids in those sources.

The studies use the concept of digestibility - a measure of how much nutrition a food provides in a given volume. It indicates how much of the food is absorbed by the gut (intestines) into the bloodstream. Because a highly digestible food provides a higher proportion of absorbed nutrients than a less digestible food, digestibility provides an important measure of a food’s nutritional value and quality.

Deeper Look into Study 1 – Golder et al. (2020) – Plant proteins improve digestibility of a diet in cats (1)

This study successfully demonstrates that cats can efficiently digest increasing dietary levels of plant-based ingredients. To illustrate the overall effect of plant protein on protein digestibility, the graph of the relationship between protein digestibility and percent of dietary protein from plants is shown in below Figure 1. 

Figure 1. The relationship between protein digestibility and % of dietary plant protein in cats.

Protein digestibility in cats was increased when protein contribution, supplied by corn gluten meal and soy protein isolate, increased from 0 to 50%. This finding clearly demonstrates that cats are capable of digesting plant-based ingredients despite their simple digestive tracts.

Deeper Look into Study 2 – Reilly et al. (2020) – Plant proteins provide high-quality amino-acids to cats (2,3)

This study at University of Illinois included a wider selection of protein sources than the previous one. Peas, beans, lentils, soybean meal, dried yeast, and corn were some of the protein ingredients studied.

Digestibility of specific amino-acids (building blocks of proteins) were measured. The studied ingredients were then classified as ‘high quality’, (>100% digestibility), moderate (50-100% digestibility) and low quality (<50% digestibility), depending on how well each amino acid was digested in cats.

Results in Table 1 demonstrate that all plant protein sources were classified as ‘high quality’ for all studied amino-acids in adult cats (with exception of methionine in faba beans, which received a score of ‘moderate quality’).

Table 1. Protein quality (DIASS digestibility) in adult cat, by ingredient source and amino-acid.

Based on these 2 studies we can say that a properly formulated plant-based diet can supply cats with nutrients/amino-acids they require, while improving overall digestion.


It is important to separate facts from fiction when selecting ingredients for cat food. While there are clearly vegan and ethical considerations in choosing a plant-based diet for feline companions, we see from research that there are also clear scientific reasons to do so.

Pet food suppliers such as ADM Animal Nutrition, who base their product formulations on science/economy, are starting to see that adding plant ingredients to cat products will create better, nutritious products for cats.

"These important findings allow pet food manufacturers to expand their pantry of potential ingredients when formulating cat foods and treats." (4)

"This expanded pantry is also beneficial as it alleviates pressure on the supply of meat and other animal-based ingredients used in today’s cat foods." (4)


  1. Golder, C.; Weemhoff, J.L.; Jewell, D.E. Cats Have Increased Protein Digestibility as Compared to Dogs and Improve Their Ability to Absorb Protein as Dietary Protein Intake Shifts from Animal to Plant Sources. Animals 2020, 10, 541. LINK
  2. Macronutrient composition and amino acid digestibility in pet diets containing pulse ingredients, Journal of Animal Science, Volume 98, Issue 6, June 2020, skaa165. LINK
  3. Lauren M Reilly, Patrick C von Schaumburg, Jolene M Hoke, Gary M Davenport, Pamela L Utterback, Carl M Parsons, Maria R C de Godoy, Use of precision-fed cecectomized rooster assay and digestible indispensable amino acid scores to characterize plant- and yeast-concentrated proteins for inclusion in canine and feline diets,Translational Animal Science, Volume 4, Issue 3, July 2020, txaa133. LINK

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