Effects of fermented sweet potato residue on nutrient digestibility, meat quality, and intestinal microbes in broilers

This study aimed to investigate the effects of different proportions of dietary fermented sweet potato residue (FSPR) supplementation as a substitute for corn on the nutrient digestibility, meat quality, and intestinal microbes of yellow-feathered broilers. Experiment 1 (force-feeding) evaluated the nutrient composition and digestibility of mixtures with different proportions of sweet potato residue (70%, 80%, 90%, and 100%) before and after fermentation. In Experiment 2 (metabolic growth), a total of 420 one-day-old yellow-feathered broilers were randomly allocated to 4 groups and fed corn-soybean meal-based diets with 0, 5%, 8%, and 10% FSPR as a substitute for corn. The force-feeding and metabolic growth experiments were performed for 9 and 70 d, respectively. The treatment of 70% sweet potato residue (after fermentation) had the highest levels of crude protein, ether extract, and crude fiber and improved the digestibility of crude protein and amino acids (P < 0.05). Although dietary FSPR supplementation at different levels had no significant effect on growth performance and intestinal morphology, it improved slaughter rate, half-chamber rate, full clearance rate, and meat color, as well as reduced cooking loss in the breast and thigh muscles (P < 0.05). Dietary supplementation with 8% and 10% FSPR increased the serum immunoglobulin M and immunoglobulin G levels in broilers (P < 0.05). Furthermore, 10% FSPR increased the Shannon index and Ruminococcaceae and Romboutsia abundances and decreased Sutterella and Megamonas abundances (P < 0.05). Spearman's correlation analysis showed that meat color was positively correlated with Ruminococcaceae (P < 0.05)and negatively correlated with Megamonas (P < 0.05). Collectively, 70% sweet potato residue (after fermentation) had the best nutritional value and nutrient digestibility. Dietary supplementation with 8% to 10% FSPR as a substitute for corn can improve the slaughter performance, meat quality, and intestinal microbe profiles of broilers. Our findings suggest that FSPR has the potential to be used as a substitute for corn-soybean meals to improve the meat quality and intestinal health of broilers.