# Optimizing Enzymatic Pretreatment of Wet-Grade Maize Distiller’s Dried Grains with Solubles and Maize Germ Meal for Enhanced Metabolizable Energy Utilization in Broilers

## TL;DR

This study shows that fermenting wet maize by-products with specific enzymes improves their energy value for chickens and reduces feed costs.

## Contribution

The study introduces an optimized enzymatic pretreatment method for wet-grade DDGS and MGM to enhance metabolizable energy in broilers.

## Key findings

- Co-fermentation with cellulase and X1 enzyme significantly increased dry matter degradation and metabolizable energy.
- Replacing 30% of the diet with fermented DDGS-MGM improved AME by 39.60% and nitrogen-corrected AME by 40.81%.
- Using 5% fermented DDGS-MGM in feed reduced costs by 20.45 RMB per metric ton.

## Abstract

Wet-grade maize distiller’s dried grains with solubles (DDGS), characterized by high moisture content, poor storability, and elevated fiber content, exhibit low nutrient digestibility. Studies have demonstrated that enzymatic–bacterial synergistic solid-state fermentation of wet-grade maize DDGS combined with supplementary substrates effectively improved dry matter solubility and enhanced metabolizable energy (ME). To address the challenges of high moisture and complex fibrous structure in wet-grade DDGS and leverage the water-holding capacity and porous properties of maize germ meal (MGM) for synergistic fermentation, this study screened optimal enzyme combinations and dosages through in vitro pre-digestion. The effects of fermented products on ME in broilers were further evaluated. Results indicated that co-fermentation with cellulase and the X1 enzyme (xylanase) significantly increased dry matter degradation and elevated ME in the wet-grade DDGS-MGM substrate.

This study addressed the challenges posed by wet-grade maize distiller’s dried grains with solubles (DDGS), which are characterized by high moisture and complex fibers that limit their storage and utilization in poultry feed. Three experiments were conducted to enhance their nutritional value through enzymatic and solid-state fermentation treatments. In vitro pre-digestion using multiple enzymes significantly improved dry matter solubility (DMS) and reducing sugar yield for maize DDGS and the ingredient maize germ meal (MGM). Using optimized parameters, wet-based DDGS-MGM was subjected to solid-state fermentation with 500 mg/kg of cellulase and 200 mg/kg of the X1 enzyme (a laboratory-developed multi-enzyme complex), and this treatment enhanced both DMS and reducing sugar yield, and the resulting fermented product was subsequently applied in further experiments. In the broiler trial, forty 22-day-old Arbor Acres broilers with similar body weights were randomly assigned to five treatment groups, including the control group, (50% DDGS + 50% MGM) unfermented group, (62.5% DDGS + 37.5% MGM) unfermented group, (50% DDGS + 50% MGM) fermented group, and (62.5% DDGS + 37.5% MGM) fermented group, with eight replicates per treatment (one broiler per replicate). Replacement of 30% of the basal diet with fermented 50:50 DDGS-MGM material significantly increased apparent metabolizable energy (AME) and nitrogen-corrected AME by 2.74 MJ/kg and 2.73 MJ/kg, respectively, corresponding to improvements of 39.60% and 40.81% compared to the unfermented control (p < 0.05). Economic analysis indicated that using 5% fermented DDGS-MGM in feed reduced cost by 20.45 RMB per metric ton. These findings demonstrate that bioprocessing can improve the utilization and economic value of maize processing by-products, although further validation under practical conditions is needed.