Multi-Omics Insights into the Impact of Fermented Wheat Bran-Soybean Meal-Broussonetia papyrifera Mixture Substance on the Gut Microbiota of Late Gestation Sows In Vitro

Comprehensive maternal nutritional interventions, particularly during late gestation, enhance perinatal outcomes and support long-term maternal-offspring health by modulating the microbiota. Fermented diets are recommended for inclusion in dietary guidelines during gestation, yet the specific metabolites after fermentation and their specific regulatory effects on gut microbiota during late gestation remain unclear. This study investigates the functional benefits of a fermented wheat bran-soybean meal-<i>Broussonetia papyrifera</i> mixed substrate (FMS) on the late-gestation gut microbiota using an in vitro fermentation model. The FMS was first fermented for 72 h with bacterial and enzymatic agents (2% <i>v</i>/<i>v</i>), then anaerobically incubated with fecal inocula from Jinhua pigs. Fermentation significantly enhanced nutritional profiles, increasing crude protein and amino acids while reducing fiber components (neutral detergent fiber, acid detergent fiber, and non-starch polysaccharide, <i>p</i> < 0.05). Metabolome analysis revealed a significant increase in the abundance of organic acids, amino acids, and short peptides in FMS, along with the enrichment of D-amino acid and sphingolipid pathways (<i>p</i> < 0.05). In addition, FMS significantly increased the abundance of <i>Limosilactobacillus</i> and <i>Lactobacillus</i>, as well as short-chain fatty acids production, compared to the unfermented group (<i>p</i> < 0.05). These findings demonstrate that fermentation pretreatment reduces fiber components, enhances flavor compounds and bioactive metabolites, thereby optimizing microbial utilization and increasing short-chain fatty acids production.