Dietary Artemisia argyi Inclusion Modulates Gastrointestinal Morphology, Immune-Related Indicators, and Bacterial Community Composition in Hu Sheep

Antibiotic-associated gastrointestinal dysbiosis can compromise microbial homeostasis and mucosal health, creating a need for natural feed additives that support gastrointestinal resilience. Artemisia argyi contains bioactive compounds with antimicrobial, antioxidant, and immunomodulatory properties, but its integrated effects on the gastrointestinal tract of ruminants remain insufficiently characterized. This study evaluated whether dietary A. argyi inclusion after a gentamicin-associated gastrointestinal disturbance modifies gastrointestinal morphology, serum immune-related indicators, intestinal inflammatory and barrier-related markers, and rumen and colonic bacterial communities in young Hu sheep. Forty one-month-old male Hu sheep were randomly allocated to four groups (n = 10 per group): control (Ctrl), gentamicin-challenge model (Model), low-inclusion A. argyi (ML, 1%), and high-inclusion A. argyi (MH, 3%). Following a 7-day modeling phase, during which Model, ML, and MH received gentamicin, and Ctrl did not, gentamicin administration was discontinued. Day 0 was defined as the baseline sampling point immediately after completion of the modeling phase. Blood was collected from all four groups on Day 0; immediately after this baseline collection, the 21-day dietary intervention began. During the intervention, Ctrl and Model received the basal diet, whereas ML and MH received the basal diet containing 1% and 3% A. argyi, respectively. Blood samples were subsequently collected from all sheep on intervention days 7, 14, and 21; therefore, serum analyses used n = 10 animals per group and repeated measurements from the same animals. Terminal tissue- and content-based laboratory analyses used n = 3 euthanized sheep per group. Dietary A. argyi inclusion was associated with improvements in selected gastrointestinal morphological indices, although responses differed by segment and inclusion level. Serum immunoglobulins and cytokines showed time- and treatment-associated patterns rather than a uniform response. Intestinal qPCR responses were gene- and segment-specific, and immunohistochemical effects differed according to marker and quantitative metric. For microbiota, selected taxa differed among groups, whereas the genus-level PCoA analyses presented in the manuscript did not detect significant global separation in either rumen (R = 0.0803, p = 0.292) or colonic (R = −0.0185, p = 0.528) communities. Overall, dietary A. argyi inclusion was associated with selected host and microbial responses after gentamicin exposure, but the effects were not uniformly dose-dependent and did not establish generalized gastrointestinal recovery or microbial functional restoration. Larger analytical sample sizes and direct functional measurements are required for confirmation.