<i>Lycium barbarum</i> Byproducts Modulate Rumen Fermentation, Enhance Digestive Enzyme Activity, and Improve Immune and Antioxidant Status in Grazing Sheep

The incorporation of functional plants rich in bioactive components or secondary metabolites as alternatives to growth promoters, such as antibiotics, in ruminant production is gaining momentum. Diet composition and structure are principal determinants of rumen microbial community structure, function, and the health status of ruminants. This study aimed to assess the impact of dietary <i>Lycium barbarum</i> byproducts on rumen fermentation parameters, digestive enzyme activity, microbial composition and proportion, and rumen health status in grazing sheep on sown pastures. The findings revealed that, compared to the control group (CON), the <i>Lycium barbarum</i> seed (LBS) and residue (LBR) groups exhibited increased proportions of acetic acid and propionic acid, while the proportions of valeric acid and isovaleric acid decreased. Activity of rumen digestive enzymes, including pepsin, pyruvate dehydrogenase (PDH), urease, aminopeptidase (Aps), and cellobiase increased, and rumen microbial diversity was altered (increased richness but not diversity). The relative abundance of beneficial bacteria such as <i>Prevotella</i> and <i>Ruminococcaceae_NK4A214_group</i> increased, whereas that of <i>Desulfovibrio</i> decreased. Furthermore, levels of total protein (TP), albumin (ALB), immunoglobulin (GLB), superoxide dismutase (SOD), and glutathione peroxidase (GSH-PX) increased, while uric acid (UA), blood urea nitrogen (BUN), and malondialdehyde (MDA) levels decreased. The active ingredients in the byproducts, including polysaccharides, polyphenols (flavonoids), and vegetable oils, exert beneficial effects by directly inhibiting pathogen proliferation, modulating intestinal microbiota composition, enhancing immune function, and mitigating oxidative stress.