A new study that evaluated the influence of plant and animal protein sources on protein digestibility in dogs and cats has weakened the critics of vegan pet food who often claim that plant-based pet food is less digestible. The study demonstrates that the digestibility of proteins improves in plant-based cat food compared with meat alternatives. 

The study, titled “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”, was co-authored by Christina Golder and James L. Weemhoff from Hill’s Pet Nutrition Inc., and Dennis E. Jewell from Kansas State University. 

Protein digestibility is a measure of how well the protein in the food is absorbed and used by the body. The study used 226 dogs and 296 cats that were fed different types of commercial pet foods that varied in their protein content and source and measured the amount of protein intake and faecal protein excretion of each companion animal.

The researchers found that cats had higher protein digestibility than dogs, regardless of whether they ate wet or dry food. The study also found that in cats, eating dry food with more plant protein was associated with increased protein digestibility (5.5% increase at 50% protein from plants in dry cat food), while in dogs, there was no effect of plant protein on protein digestibility. Another result is that different types of grains and plant protein fractions had variable effects on protein digestibility in both species. For example, whole rice grain had a positive effect in dogs but a negative effect in cats, while corn gluten meal had a positive effect in cats but no effect in dogs.

The authors suggest that plant proteins are similar to animal proteins in protein digestibility when prepared and extruded as in these foods and that they can provide a satisfactory source for meeting the amino acid needs of companion animals. The article also suggests that cats have an increased ability to digest plant proteins compared to dogs, which may be related to their higher overall protein digestibility. 

“Originally from Catalonia, but resident in the UK for several decades, Jordi is a vegan zoologist and author, who has been involved in different aspects of animal protection for many years. In addition to scientific research, he has worked mostly as an undercover investigator, animal welfare consultant, and animal protection campaigner. He has been an ethical vegan since 2002, and in 2020 he secured the legal protection of all ethical vegans in Great Britain from discrimination in a landmark employment tribunal case that was discussed all over the world. He is also the author of the book, ‘Ethical Vegan: a personal and political journey to change the world’.