Puerarin has been suggested to improve ruminant productivity, but its effects on rumen fermentation and rumen microbiota in sheep remain insufficiently understood. In this study, Hu sheep were fed diets supplemented with 0, 50, 100, 200, 400, or 800 mg/kg puerarin for 30 d to evaluate growth performance, apparent nutrient digestibility, serum biochemical and antioxidant indices, rumen fermentation, and rumen microbial community structure. Puerarin supplementation improved growth performance, with the 100 mg/kg group showing the greatest average daily gain. Acid detergent fiber digestibility was also significantly increased in the 100 mg/kg group. In the rumen, microbial crude protein concentration was significantly increased in the 100 and 400 mg/kg groups, propionate concentration was significantly increased in the 50 and 100 mg/kg groups, and the acetate-to-propionate ratio was significantly decreased in the 100 mg/kg group. In serum, albumin and glucose concentrations were significantly increased at appropriate supplementation levels, whereas malondialdehyde was reduced in the 100 mg/kg group but increased in the 800 mg/kg group. 16S rRNA sequencing showed limited effects on overall bacterial diversity, but changes in specific rumen microbial taxa and predicted microbial functions were observed. Collectively, these findings suggest that dietary puerarin, particularly at 100 mg/kg, may improve growth performance in Hu sheep, at least in part, through improving rumen fermentation.

Weaning stress is a major challenge in lamb production, triggering oxidative damage, immune suppression, and gastrointestinal barrier disruption. Therefore, safe and effective nutritional strategies are urgently needed to alleviate weaning-stress-induced injuries. This study aimed to investigate the influences of dietary Jianpi Herbal Formula (JHF) on immunity, gastrointestinal barrier function and nutrient absorption in weaned Hu lambs. One hundred weaned Hu lambs (male, 14.55 ± 0.21 kg) were randomly allotted to five groups (four replicates per group, five lambs per replicate; 20 per treatment) for a 60-day trial, receiving basal diet (control), or basal diet supplemented with 0.3% and 0.5% of two JHFs (JHF I and JHF II). Compared with the control group, dietary supplementation with 0.3% and 0.5% JHF I increased serum immunoglobulin G level by 25.1% and 24.5% (p < 0.05) and glutathione peroxidase activity by 16.3% and 10.6% (p < 0.05), while decreasing malondialdehyde content by 26.5% and 28.7% (p < 0.05) and diamine oxidase activity by 20.7% and 21.0% (p < 0.05), respectively. Dietary 0.5% JHF I also increased papilla width by 26.8% and the thickness of the stratum granulosum and total epithelium in the Saccus dorsalis by 16.5% and 10.8% (p < 0.05), respectively, and decreased stratum corneum thickness in both ruminal sacs (p < 0.05). Furthermore, 0.5% JHF I upregulated mRNA expression of Occludin and MCT1 in both ruminal sacs, Claudin-1, DRA, and NHE3 in the Saccus ventralis, ZO-1 in the ileum, and SGLT1 and GLUT2 in the jejunum (p < 0.05). It also increased duodenal maltase and jejunal sucrase activities and elevated protein expression of Occludin and MCT1 in the Saccus dorsalis, ZO-1 in the ileum, and GLUT2 in the jejunum (p < 0.05). In conclusion, dietary supplementation with 0.5% JHF I effectively enhanced antioxidant capacity and immune function, increased intestinal digestive enzyme activities, improved ruminal epithelial morphology, protected gastrointestinal barrier integrity, and upregulated nutrient transporter expression, thereby alleviating weaning stress in Hu lambs.