Thesis

Necrotic enteritis is a critical intestinal disease in poultry, and its occurrence is closely associated with the overgrowth of Clostridium perfringens (Cp). With the trend toward reducing antibiotic use , alternative phytogenics with safe and practical applications for sustainable poultry production have become an important focus in poultry industry. Zanthoxylum ailanthoides (ZA), a native plant in Taiwan, contains various bioactive compounds and possesses antioxidant, anti-inflammatory, and antibacterial properties, suggesting its potential as a phytogenic feed additive. This study investigated the effects of dietary supplementation of ZA leaf powder on growth performance and intestinal health in red-feather country chickens under Cp challenge. A total of 200 one-day-old commercial male chicks were randomly assigned to five groups: a non-challenged control group, a Cp-challenged control group, and groups supplemented with 0.25%, 0.5%, or 1% ZA leaf powder. Each group consisted of four replicates with 10 birds per replicate. At 3, 5, and 8 weeks of age, birds were orally administered 1, 1.5, or 2 mL of Cp (2 × 10⁸ CFU/mL), respectively, whereas birds receiving an equal volume of saline served as a control. Birds were sacrificed for sample collection at 4, 7, and 12 weeks of age. The results showed that dietary supplementation with 0.25% ZA improved growth performance including body weight gain, feed intake and feed conversion rate. Supplementation with 0.25% and 0.5% ZA alleviated jejunal and ileal injury, as shown by significantly reduced lesion scores, with the 0.5% group exhibiting the most pronounced effect. In intestinal health, Cp challenge increased IL-1β levels in the serum, jejunum, and ileum and damaged intestinal integrity, whereas ZA supplementation reduced these inflammatory responses. In addition, supplementation with 0.25% and 0.5% ZA increased intestinal IgA concentrations and differentially upregulated antimicrobial peptide gene expressions, suggesting enhanced mucosal innate immunity. Furthermore, ZA supplementation reduced intestinal permeability, as indicated by serum FITC-dextran concentrations, and increased Claudin-1 protein expression in the jejunum and ileum, indicating improved mucosal integrity and barrier stability. In conclusion, ZA as a locally sourced phytogenic feed additive, has a great potential to improve growth performance, alleviate intestinal damage, reduce inflammatory responses, and maintain intestinal barrier function in red-feather country chickens under Cp infection. Among the tested supplementation levels, 0.25% and 0.5% demonstrated superior beneficial effects. These findings suggest that ZA has a considerable potential as a natural alternative feed additive for antibiotic-free poultry production.

Keywords: Zanthoxylum ailanthoides; Clostridium perfringens; red-feather country chicken; intestinal health; growth performance