Effects of Dietary Dandelion Supplementation on Ruminal Morphology, Fermentation, Microbiome, and Inflammation in Lambs Under High-Concentrate Feeding

This study aimed to investigate the regulatory effects of dietary dandelion supplementation on the ruminal physiological status of lambs fed a high-concentrate diet. Twenty-two 6-month-old female crossbred lambs with an initial body weight of 32.05 ± 0.43 kg were randomly assigned to two groups (n = 11 per group): the HC group (fed a high-concentrate basal diet) and the DD group (basal diet supplemented with 2 g/kg dandelion powder), with a 14-day adaptation and 60-day experimental period. The results showed that compared with the HC group, dandelion supplementation significantly improved lamb growth performance and modulated ruminal fermentation parameters and tissue morphology. For inflammatory indices, the concentration of interleukin-10 (IL-10) was significantly increased, while the concentrations of interleukin-1β (IL-1β), lipopolysaccharide (LPS) and histamine (HIS) were significantly decreased (p < 0.05). Meanwhile, dandelion supplementation upregulated the mRNA expression of ruminal epithelial tight junction proteins and hexokinase II (HK-II), while downregulating the mRNA expression of myeloid differentiation factor 88 (MyD88), voltage-dependent anion channel 1 (VDAC1), inositol 1,4,5-trisphosphate receptor (IP3R), NLR family pyrin domain containing 3 (NLRP3), and caspase-1. Metagenomic analysis revealed that dandelion supplementation did not alter ruminal microbial α-diversity, but slightly modulated community composition and functional profiles. The abundances of dominant phyla Bacteroidota and Bacillota showed only slight fluctuations, while fiber-degrading genera (Xylanibacter, Quinella, Selenomonas) showed a trend toward enrichment, and proteolytic taxa were decreased. CAZyme analysis revealed an upward trend in families CE4, CE8, GH32, and GH13_46 (pectin/starch degradation) and a downward trend in GH73, GH27, and GT14 (oligosaccharide/peptidoglycan/polysaccharide metabolism) in the DD group. KEGG orthology annotation suggested that nominal KO differences were mainly associated with carbohydrate metabolism pathways, including starch and sucrose metabolism and peptidoglycan biosynthesis. None of these features, however, remained significant after FDR correction (raw p < 0.05; all q > 0.05). Collectively, dietary dandelion supplementation was associated with alterations in ruminal physiological status and microbial community in lambs fed a high-concentrate diet, providing foundational data for dandelion application in lamb diets under short-term feeding conditions.