Evaluation of nutritive value of sorghum-based fermented distiller's dried grain and its effects on growth...

This study aimed to evaluate the nutritive value of sorghum-based fermented distiller's dried grains (FDG) and quantify their dose-response effects on growth performance, nutrient digestibility, intestinal morphology, and cecal microbial communities in broilers. (1) Nutritional composition, amino acid, soluble sugar, and untargeted metabolomics of distiller's dried grains (DDG) and FDG samples were analyzed. Results showed that FDG had a higher crude protein (CP) and lower crude fiber (CF) content than unfermented DDG (P < 0.05). The concentrations of most hydrolyzed amino acids (AA) and soluble sugars were markedly increased in FDG (P < 0.05). Untargeted metabolomics identified 169 differential metabolites between DDG and FDG, with FDG enriched in bioactive compounds including "polyphenols and flavonoids", "nucleosides, nucleotides and analogs" and "organic acids and derivatives," whereas "alkaloids and derivatives" were downregulated. (2) Furthermore, in vitro monogastric simulated digestion and in vivo total excreta collection assays using 21-day-old broilers demonstrated that fermentation significantly improved apparent CP and CF digestibility. (3) For the feeding trial, a total of 540 1‑day‑old male AA broilers with an average initial body weight of 38.79 ± 0.14 g were randomly allocated into six dietary treatments with 6 replicates per treatment and 15 birds per replicate, and the trial lasted for 42 d. The dietary treatments included a basal diet supplemented with 0% (F0), 2.5% (F2.5), 5% (F5), 10% (F10), 15% (F15), or 20% (F20) FDG, respectively. Growth performance results showed that F2.5-F5 groups maintained growth performance comparable to that of the control group, whereas 20% FDG supplementation markedly impaired F/G (P < 0.05) across all growth phases. Serum biochemistry indicated that FDG supplementation up to 15% had no adverse effects on liver and kidney function, but 20% FDG increased alanine aminotransferase and aspartate aminotransferase activities (P < 0.05). Intestinal morphology analysis revealed that 20% FDG deepened jejunal crypt depth and reduced villus height/crypt depth (V/C) ratio (P < 0.05), whereas F0-F15 groups maintained normal intestinal architecture. Cecal microbiota analysis showed that 2.5%-5% FDG increased microbial diversity (Shannon index) and enriched beneficial genera (Butyricicoccus, Lactobacillus, Faecalibacterium), whereas 20% FDG promoted the proliferation of Escherichia-Shigella (P < 0.05). In conclusion, fermentation effectively enhances the nutritive value of sorghum-based DDG. Supplementation with 2.5%-5% FDG maintained growth performance comparable to that of the control while improving gut health; 10% FDG can be used for soybean meal replacement in practical production without compromising performance; and the maximum safe inclusion level is 15% in broiler diets.