Gentiana scabra mitigates Eimeria tenella-induced Coccidiosis by regulating the gut microbiota-metabolome and strengthening the intestinal barrier.

Coccidiosis is a major parasitic threat to global poultry production. Chemical anticoccidial overuse raises residue and food safety concerns, spurring interest in safe, residue-free alternatives like Chinese herbal medicines. Gentiana scabra extract (GSE) shows broad bioactivity, but its anticoccidial efficacy against Eimeria tenella and gut microecological effects remain unclear. We evaluated three GSE doses (1, 2, 4 g/kg feed) in a controlled floor-pen experiment using broilers infected with E. tenella. Anticoccidial activity was assessed via McMaster oocyst counting and clinical indices: oocysts per gram (OPG), relative body weight gain (RBWG), survival rate (SR), and anticoccidial index (ACI). GSE alleviated intestinal lesions, improved SR and RBWG, Nand reduced OPG in a nonlinear, dose-dependent manner. The 2 g/kg dose achieved optimal efficacy (ACI = 163.5; moderate activity); lower (1 g/kg, ACI = 149.5) and higher (4 g/kg, ACI = 146.1) doses were less effective. GSE enhanced gut microbial α-diversity and richness, increased beneficial taxa (e.g., Butyricicoccus, Lachnospiraceae) and metabolites, and suppressed pathogens (Clostridium perfringens, Tyzzerella)-most robustly at 2 g/kg. Differential metabolites mapped predominantly to energy metabolism (pyruvate, TCA cycle) and host signaling (PI3K-AKT, mTOR, AMPK). This is the first study to demonstrate GSE's anticoccidial potential and link it mechanistically to gut microbiota-metabolome modulation-supporting its development as a multi-target, natural anticoccidial alternative.