Effects of recombinant Xylanase Xyn1m on growth performance, Intestinal morphology, and bacterial community structure in broilers

This study evaluated the effects of recombinant xylanase Xyn1m, derived from Fibrobacter succinogenes and expressed in Pichia pastoris, on growth performance, intestinal morphology, and gut microbial characteristics in broilers. A total of 144 one-day-old broilers were randomly allocated to three treatments with 12 replicates per treatment (4 birds per replicate): a control group (basal diet), a low-dose Xyn1m group (6,800 IU/kg), and a high-dose Xyn1m group (13,600 IU/kg). Supplementation with high-dose Xyn1m significantly increased body weight at 49 d and average daily gain during the 29-49 d growth phase compared with the control group (P< 0.01), whereas feed intake and feed conversion ratio were not affected. High-dose Xyn1m reduced duodenal crypt depth (P< 0.05), while ileal morphology remained unchanged. In the duodenum, Xyn1m supplementation increased the Shannon index and reduced the Simpson index of the microbial community (P< 0.05), although no significant differences were detected in the relative abundance of dominant bacterial taxa. Beta-diversity analysis showed that high-dose Xyn1m altered the duodenal microbial community structure. In contrast, no significant differences were observed in microbial diversity or community composition in the ileum, except for a linear reduction in the relative abundance of Acinetobacter (P< 0.05). Functional prediction using PICRUSt2 indicated enrichment of pathways associated with nutrient transport, carbohydrate metabolism, and energy production in the duodenal microbiota of the high-dose group, whereas predicted functional changes in the ileum were limited. These results indicate that dietary supplementation with 13,600 IU/kg recombinant xylanase Xyn1m improved growth performance during the mid-growth stage and enhanced duodenal microbial diversity and intestinal morphology, while exerting minimal effects on distal ileal microbial functions.