The synergistic effects of inulin and rumen-bypass fat on host immunity, bile acid profiles, and gut microbiota in weaned goats.

BACKGROUND

Weaning is a critical developmental stage in young ruminants, marked by nutritional and immunological stress that may hinder growth and health. This study investigated the combined effects of dietary inulin and rumen-bypass fat on bile acid metabolism, gut microbiota, and mucosal immunity in weaned goats. Eighteen 3-month-old Liuyang black goats (8.97 ± 0.19 kg) were randomly assigned to two isoenergetic diets for 35 days: a control corn-based diet (CON) or a high-fat inulin diet (INU), containing 144 g kg-1 rumen-bypass fat and 189 g kg-1 inulin. Colonic chyme, liver, ileum, and colon tissues were analyzed for microbial diversity (16S rRNA sequencing), bile acid profiles, gene expression, and inflammatory markers.

RESULTS

The INU diet significantly improved colonic microbial diversity, indicated by higher Shannon and Simpson indices (P < 0.05). It increased beneficial taxa such as Lachnospiraceae_NK3A20_group (P = 0.005) and Olsenella (P = 0.028), while reducing the pro-inflammatory genus Mycoplasma (P < 0.05). Bile acid metabolism was modulated, with reductions in primary bile acids (glycocholic acid, taurocholic acid; P < 0.05), secondary bile acids (12-ketolithocholic acid, glycodeoxycholic acid; P < 0.05), and an increase in taurocholic acid (P < 0.05). Hepatic and colonic expression of bile acid regulators (farnesoid X receptor, pregnane X receptor) and transporters (apical sodium-dependent bile salt transporter, organic solute transporter-α) was downregulated (P < 0.01), suggesting improved enterohepatic circulation. Inulin activated colonic toll-like receptor 4 (TLR4) signaling, upregulating myeloid differentiation primary response gene 88-dependent (interleukin-1 receptor-associated kinase, TIRAP, TAB2, nuclear factor κB) and toll-containing interleukin-1 receptor domain adaptor protein (TRIF)-dependent (TRIF, TBK1, interferon β) pathways (P < 0.05), while suppressing interferon regulatory factor 5 (P < 0.05) and elevating inflammatory markers (interleukin 6, interleukin 12 beta, NLRP3; P < 0.05), indicating a balanced immune response that supports mucosal development.

CONCLUSION

The synergistic effects of inulin and rumen-bypass fat reshape gut microbiota, optimize bile acid metabolism, and enhance TLR4-mediated immunity, offering a novel dietary strategy to improve intestinal health and resilience in weaned ruminants. © 2025 Society of Chemical Industry.