Effects of an Astragalus membranaceus Stem and Leaf-Angelica sinensis Stem and Leaf Mixture on Serum Parameters, Gut Microbiota, and Metabolomic Profiles in Simmental Weaned Bull Calves.

This study evaluated the effects of an Astragalus membranaceus stem and leaf-Angelica sinensis stem and leaf mixture (AASL) as a medicinal feed supplement on immune function, antioxidant status, inflammatory responses, gut microbiota and the serum metabolome in weaned Simmental bull calves. Calves were fed diets containing different levels of AASL, and serum immunoglobulins, inflammatory cytokines, and antioxidant indices were determined. In addition, fecal short-chain fatty acid (SCFA) concentrations, gut microbiota composition, and serum metabolic profiles were analyzed, followed by correlation analyses among the microbiota, SCFAs and metabolites. The results showed that AASL was rich in crude protein, crude fat and trace elements. 4% AASL supplementation increased serum immunoglobulin (IgG and IgM) levels, decreased tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6) and interleukin-1 beta (IL-1β) levels, and enhanced superoxide dismutase (SOD), glutathione (GSH) and total antioxidant capacity (T-AOC) activities (p < 0.01 or p < 0.001), indicating improved immune and antioxidant status and attenuated inflammatory responses. AASL also enriched beneficial bacterial genera, suppressed potentially harmful taxa, and increased SCFA concentrations. Differential metabolites were mainly enriched in tryptophan metabolism, lipid metabolism, neuroactive ligand-receptor interaction, sphingolipid signaling, and ATP-binding cassette (ABC) transporter pathways. Integrated microbiota metabolite analysis further suggested that AASL improved host metabolic status through the coordinated regulation of gut microbiota, SCFAs production and related metabolic pathways. Overall, AASL shows promise as a functional feed supplement for improving calf health.