Microbial-Enzymatic Co-Fermentation of Feather Meal for Bioactive Peptide Production and Its Multi-Pathway Synergistic Regulation of Intestinal Health in Broilers

The nutritional quality of feather meal ( FM ) is constrained owing to its elevated keratin content and unbalanced amino acid ( AA ) composition, while small peptide substances have beneficial effects on animal growth promotion, immune enhancement, and intestinal function modulation. Herein, the goal of this work was to fabricate bioactive peptides by microbial-enzyme co-fermentation of feather meal and to explore the effects of fermented feather meal ( FFM ) rich in bioactive peptides on the growth performance and intestinal health of broilers. In total, 450 healthy one-day-old Arbor Acres broilers were randomly divided into 5 dietary treatments, including 6 replicates per treatment and 15 birds per replicate for 42 d. The treatments were as follows: a basal diet (CON), 2% (FM1) and 4% (FM2) feather meal, and 2% (FFM1) and 4% (FFM2) fermented feather meal, with soybean meal ( SBM ) replaced under isonitrogenous conditions. Dietary supplementation with 4% FM reduced broiler body weight, average daily gain, and thigh muscle percentage while increasing feed conversion ratio, and these adverse effects were notably alleviated by FFM relative to the FM2 group ( P < 0.05). Moreover, relative to the FM2 group treatment with 4% FFM improved serum immunoglobulin and antioxidant indices ( P < 0.05), and both FM and FFM supplementation resulted in higher serum IL-10 concentrations relative to the CON group ( P < 0.05). In addition, relative to the CON and FM groups, supplementation with 4% FFM markedly improved intestinal morphology, reduced intestinal permeability, upregulated the expression of intestinal barrier-related genes and proteins, regulated the Nrf2/PI3K/NF-κB pathways and activated intestinal peptide/AA transporters ( P < 0.05). FFM also effectively increased the cecal probiotics such as Lactobacillus and reduced the pathogenic taxa including Escherichia-Shigella ( P < 0.05). Overall, intestinal health can be effectively improved by FFM through the synergistic action of multiple pathways, with 4% inclusion showing the best effects among the tested levels. These findings provide a scientific reference for the high-value utilization of feather resources.