Effects of Dietary Chinese Herbal Formula on Immune Capacity, Gastrointestinal Barrier Function and Nutrient Utilization in Weaned Hu Lambs

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.