Effects of dietary fiber sources on nitrogen metabolism and fecal microbiota in growing-finishing pigs.

Nitrogen metabolism in pigs is closely associated with gut microbiota, but the differential effects of dietary fiber sources on nitrogen metabolism and gut microbiota remain unclear. This study investigated the effects of pectin, β-glucan, arabinoxylan, and cellulose on nitrogen metabolism, fecal microbiota, and metabolic characteristics in growing-finishing pigs. Sixty healthy castrated male pigs (initial body weight 44.32 ± 0.29 kg) were randomly assigned to five groups (n = 12 per group) for a 28-day trial, receiving a basal diet supplemented with 7.0% wheat bran (CON group), 3.5% pectin (PC group), 3.5% β-glucan (BG group), 3.5% arabinoxylan (AX group), or 3.5% cellulose (CL group). Compared with the CL group, the PC and AX groups had significantly higher blood ammonia (BLA) and urea nitrogen (BUN) levels (P < 0.05). Compared with the CON and CL groups, the PC, BG, and AX groups had significantly higher fecal nitrogen (N) content (P < 0.05). Different fiber sources significantly altered the composition and functional potential of the fecal microbiota, leading to changes in key genera including Limosilactobacillus, Lactobacillus, and Escherichia-Shigella (P < 0.05). Compared with the CL group, the PC group exhibited higher microbial nitrogen cycling-related functions, fecal microbial protein (MCP), and ammonia nitrogen concentrations (P < 0.05). In conclusion, different dietary fiber sources exert differential effects on nitrogen metabolism and fecal microbiota in growing-finishing pigs. Pectin and cellulose induce distinct changes in nitrogen excretion through modulation of the gut microbiota, offering insights into using plant fiber byproducts to reduce nitrogen pollution in swine production.