# Evaluation of Graded Levels of Fermented Plant Protein (Proteger®) on Extrusion Processing and Diet Utilization in Young Cats

## TL;DR

This study shows that fermented plant protein improves extrusion processing and diet utilization in cats compared to soybean meal.

## Contribution

The novel finding is that fermented plant protein can replace soybean meal in cat diets without compromising digestibility or stool quality.

## Key findings

- Fermented plant protein inclusion up to 15% did not affect processing or stool quality in cats.
- Cats preferred diets with 10% fermented plant protein over soybean meal.
- Fermented plant protein improved protein digestibility and reduced hind-gut fermentation.

## Abstract

Soybean meal is a common plant-based protein ingredient in extruded pet foods. However, a high inclusion level of soybean meal in pet food is limited by antinutritional factors, including trypsin inhibitors and oligosaccharides, that compromise protein digestibility, stool quality and cause flatulence in cats. Our animal study found that inclusion of a fermented plant protein product at 10% in a cat diet promoted kibble expansion; and had comparable protein digestibility, less hind-gut fermentation and greater palatability with ideal stool quality in cats when replacing traditional soybean meal by 10 out of 15% of the formula. We suggest that fermentation with Aurobasidium pullulans was an effective method to improve soybean meal nutritional value, hence increasing the inclusion level in extruded cat foods.

This study evaluated fermented plant protein (FPP) for extrusion performance and its effects on diet utilization in adult cats. Four diets were formulated: a control with 15% soybean meal (SBM) and three diets replacing soybean meal at 5%, 10%, and 15% with FPP (5FPP, 10FPP, and 15FPP). Diets were extruded using a single-screw extruder, with data and samples collected at 15 min intervals. Twelve cats participated in a 4 × 4 Latin square design, with 9 days of diet adaptation followed by 5 days of total fecal collection for nutrient digestibility and colonic fermentation analysis. Processing effects of FPP inclusion were minimal. The kibble sectional expansion index was lowest for SBM (2.50) and highest for 15FPP (2.82; p < 0.05). Fecal moisture increased (p < 0.05) in cats fed 15FPP. The apparent total tract digestibility of protein was greatest (p < 0.05) in cats fed 15FPP. The fecal ammonia concentrations increased linearly (p < 0.05) with FPP, while total fatty acid concentrations were lower (p < 0.05) in cats fed 10FPP compared to SBM. Cats preferred (p < 0.05) 10FPP over SBM as measured by the intake ratio. The FPP inclusion (up to 15%) did not adversely affect processing, stool quality, or nutrient digestibility. Diets with 5–10% FPP tended to reduce hind-gut fermentation.