# Potential of citric and yeast waste fermentation products supplemented with fiber-degrading enzymes as alternatives to soybean meal in ruminant nutrition

## TL;DR

This study explores using citric and yeast waste with enzymes as a sustainable alternative to soybean meal in ruminant feed.

## Contribution

The novel contribution is evaluating citric waste fermented yeast waste supplemented with fiber-degrading enzymes as a soybean meal replacement.

## Key findings

- Control diets had the highest gas production and digestibility.
- CWYW with 0.4% enzyme produced fermentation and digestibility comparable to the control.
- Enzyme supplementation linearly decreased pH and increased NH₃-N concentrations.

## Abstract

This study aimed to investigate the effects of fiber-degrading enzyme supplementation in combination with citric waste fermented yeast waste (CWYW) as a replacement for soybean meal on ruminal fermentation characteristics, gas production kinetics, and digestibility. The in vitro gas production technique was used to evaluate these effects. A 2 × 4 + 1 factorial arrangement in a completely randomized design (CRD) was employed, resulting in nine treatments comprising either CWYW in powder or pellet form with varying enzyme levels (0%, 0.2%, 0.4%, and 0.6%), alongside a control diet containing full soybean meal.

The control diet yielded the highest cumulative gas production (P < 0.01), whereas the CWYW-powder without enzyme addition showed the highest gas production rate constant (P < 0.01). The in vitro dry matter digestibility (IVDMD) was also highest in the control group (P < 0.01), while organic matter digestibility (OMD) did not differ significantly among treatments. Increasing levels of fiber-degrading enzymes were associated with a linear decrease in pH at 48 h (P < 0.05) and a corresponding increase in NH₃-N concentrations (P < 0.05). However, there were no statistically significant differences among CWYW treatments in most parameters.

Although the control diet performed best in terms of gas production and digestibility, the combination of CWYW and 0.4% fiber-degrading enzyme supplementation produced fermentation characteristics and digestibility values comparable to those of the control. These findings suggest that CWYW, particularly when supplemented with 0.4% enzyme, holds potential as a sustainable alternative to soybean meal in ruminant feed formulations.