Bamboo leaf flavonoids modulate the colonic host-microbiome interface in goat kids to enhance immune function

Bamboo leaf flavonoids (BLF) exhibit multiple nutritional and biological benefits for animals; however, the impact of these compounds on goat kids has not been fully elucidated. This research assessed the impacts of BLF on blood immunity, colonic metabolites, microbial composition, and barrier functions in goat kids. A total of 64 goat kids (10 days old, initial body weight of 3.77 ± 0.60 kg) were randomly assigned to four dietary treatments: milk only (CON), milk supplemented with BLF at 30 mg/kg body weight (LBLF), milk supplemented with BLF at 60 mg/kg BW (MBLF), and milk supplemented with BLF at 120 mg/kg BW (HBLF). The findings indicated that BLF-treated groups had a significantly lower frequency of diarrhea over the 50-day experimental period compared to the CON group. Goat kids in the MBLF group exhibited significantly higher serum levels of the cytokines IL-2 and IL-4 compared to the CON group ( P < 0.05), whereas no significant differences were detected in IL-6, IL-1β, or TNF-α levels ( P > 0.05). Furthermore, the MBLF group showed elevated serum IgG levels ( P < 0.05), while IgM and IgA levels remained unchanged relative to the CON group ( P > 0.05). The MBLF group had a greater colon length than the CON, LBLF, and HBLF groups. Qualitative histological examination suggested a comparatively well-organized colonic morphology in the MBLF group. BLF supplementation significantly reshaped colonic metabolite profiles and increased the relative abundance of metabolites annotated to the KEGG flavone and flavonol biosynthesis pathway; these metabolic changes were associated with improved immune function and anti-inflammatory capacity in goat kids. Additionally, BLF supplementation altered the colonic microbial community structure and increased the relative abundance of dominant bacteria linked to a healthy intestinal tract. Meanwhile, the expression of junction-related genes—including ZO-1, claudin-2, claudin-1, and occludin—was significantly upregulated in the colon tissue. In conclusion, these results demonstrate that BLF enhances intestinal health and immune function in goat kids. This protective effect may be mediated through alterations in gut metabolites, which subsequently promote the enrichment of beneficial microbes and modulate host immune responses.