Abstract
Background and aim: The global ban on antibiotic growth promoters in poultry production has accelerated the search for safe and effective natural alternatives. Polysaccharides derived from traditional Chinese medicinal plants have shown promise due to their antioxidant and immunomodulatory properties. This study evaluated the efficacy of dietary Scutellaria baicalensis polysaccharide (SBP) as an alternative to in-feed antibiotics by assessing its impact on growth performance, antioxidant status, digestive function, intestinal morphology, and mucosal immunity in broiler chickens. Materials and methods: A total of 420 one-day-old Arbor Acre broilers were randomly assigned to five dietary treatments for 42 days, with six replicates per treatment. The treatments included an antibiotic-free basal diet (control), a basal diet supplemented with colistin sulfate and virginiamycin (antibiotics), and the basal diet supplemented with SBP at 100 mg/kg (SBP-L), 200 mg/kg (SBP-M), or 400 mg/kg (SBP-H). Growth performance parameters were recorded, and on days 21 and 42, serum and intestinal antioxidant indices, digestive enzyme activities, intestinal morphology, secretory immunoglobulin A (sIgA) levels, and the expression of immune-related genes (C-C motif chemokine ligand 28 [CCL28], A proliferation-inducing ligand (tumor necrosis factor ligand superfamily member 13) [APRIL]) and toll-like receptor 4 protein were evaluated. Results: Dietary SBP supplementation significantly improved average daily gain (ADG) and feed conversion ratio during the starter phase without affecting feed intake or mortality (p < 0.05). Over the entire 42-day period, broilers fed 400 mg/kg SBP showed a 3.4% higher ADG than those receiving antibiotics (p < 0.05). SBP boosted systemic and intestinal antioxidant capacity by increasing glutathione peroxidase, glutathione reductase, Superoxide dismutase, and total antioxidant capacity activities while lowering malondialdehyde levels (p < 0.05). Additionally, SBP increased digestive enzyme activities, improved villus height-to-crypt depth ratios, and raised sIgA concentrations in the duodenum and jejunum. The upregulation of TLR4 protein and the immune-related genes CCL28 and APRIL indicated enhanced intestinal mucosal immunity, especially in the SBP-M and SBP-H groups. Conclusion: Dietary supplementation with S. baicalensis polysaccharide, especially at 200-400 mg/kg, effectively improves growth performance, antioxidant defense, and intestinal health in broilers, demonstrating its strong potential as a practical and sustainable alternative to antibiotic growth promoters in poultry production.