Fermented soybean meal improved laying performance and egg quality of laying hens by modulating cecal microbiota, nutrient digestibility, intestinal health, antioxidant and immunological functions

Antinutritional factors in feedstuffs may limit their utilization in livestock production, but fermentation process can be used to improve feed quality; however, studies on fermented soybeans for laying hens remain limited. We investigated the effect of fermented soybean meal (FSBM) at various inclusion levels as a partial replacement for soybean meal (SBM) on egg production, egg quality, amino acid digestibility, gut morphology and microbiota, antioxidant capacity and immune response of young laying hens. A total of 360 Hy-line Brown laying hens aged 18 weeks were selected and divided into 5 groups of 6 replicates each and 12 birds per replicate. The control group received a basal diet while the trial group received the basal diet with FSBM included at 2.5%, 5.0%, 7.5% and 10.0%, respectively, for 12 weeks. Our findings revealed that the nutritional value of FSBM was higher compared to that of SBM in terms of reduced content of trypsin inhibitors and increased contents of crude protein, amino acids and minerals. FSBM enhanced egg production (P < 0.05), feed-to-egg ratio (P < 0.05), and albumen quality (albumen height and Haugh unit) (P < 0.05). Furthermore, FSBM improved apparent fecal amino acid digestibility (P < 0.05), gut morphology (increased villus height, villus width, villus height-to-crypt depth ratio and decreased crypt depth) (P < 0.05), antioxidant capacity (reduced malondialdehyde and increased catalase, total superoxide dismutase, glutathione peroxidase and total antioxidant capacity) (P < 0.05) and immune function (increased concentrations of IgG, IgA, and IgM; increased levels of transforming growth factor beta and Toll-like receptor 2; and reduced levels of interlukin 1β and tumor necrosis factor alpha) (P < 0.05). Further analysis showed that FSBM altered the composition of the gut microbiota favoring beneficial microbes. These findings suggest that probiotic fermentation improved the nutritional value of SBM. The inclusion of FSBM in the diets of laying hens at 2.5% or 5.0% improved amino acid digestibility, gut health, immune function, egg production and egg quality.