Dietary supplementation with fermented compound Chinese herbal medicine reshapes the gastrointestinal microbiota and enhances growth in suckling lambs.

UNLABELLED: This study investigated the effects of a fermented compound Chinese herbal medicine (FCHM) on growth performance, antioxidant capacity, immune function, and gastrointestinal microbiota in suckling lambs. FCHM consisted of 10 herbs fermented with Candida utilis and Bacillus subtilis. Sixty twin Hu lambs (15 days) were randomly fed a basal diet (CON) or the diet supplemented with 0.6% FCHM (Treat) for 45 days. The results indicated that the Treat group exhibited a significant increase in average daily gain (ADG) (P < 0.05). Serum analyses revealed elevated levels of growth hormone (GH), insulin-like growth factor-1 (IGF-1), total antioxidant capacity (T-AOC), superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and glucose (GLU), whereas malondialdehyde (MDA) and pro-inflammatory cytokines (IL-6 and TNF-α) were reduced (P < 0.05). In the duodenal mucosa, SOD and GSH-Px activities and T-AOC levels were significantly elevated, while MDA content was notably decreased (P < 0.05). Ruminal fermentation profiles showed increased concentrations of propionate and total volatile fatty acids (TVFA) in the Treat group (P < 0.05). Microbiome analysis revealed that FCHM supplementation selectively modulated the ruminal microbial community, enriching beneficial genera such as Prevotellaceae_UCG-003 and Butyrivibrio, while reducing the abundance of potentially harmful genera like Streptococcus, despite no significant changes in the overall community diversity. Metagenomic sequencing further demonstrated the enrichment of KEGG enzymes and carbohydrate-active enzyme genes involved in carbohydrate metabolism and propionate biosynthesis. Correlation network analyses revealed significant associations among specific microbial taxa, serum antioxidant, immune biomarkers, and growth performance. In conclusion, dietary FCHM supplementation improves growth performance in suckling lambs by optimizing ruminal fermentation patterns, selectively regulating gastrointestinal microbiota, and enhancing systemic antioxidant capacity. These findings support the potential of FCHM as a functional feed additive in lamb production systems.

IMPORTANCE: Enhancing growth performance and ensuring gastrointestinal health during the suckling period are critical for lamb productivity and welfare. In the context of the antibiotic-free mandate in animal feed, we evaluated the effects of a fermented compound Chinese herbal medicine (FCHM) on growth, antioxidant status, immune parameters, and gastrointestinal microbiota in lambs. Our findings demonstrate that FCHM improves average daily gain, enhances systemic and mucosal antioxidant capacity, and modulates ruminal and hindgut microbiota by enriching beneficial taxa and suppressing potentially harmful bacteria. These effects are linked to upregulated microbial functions in carbohydrate metabolism and propionate biosynthesis. This study provides a microbial-based mechanism for FCHM as a natural feed additive to promote lamb growth and gastrointestinal resilience, offering a sustainable strategy to support early-life development in ruminant production systems.