Abstract
Objective: To evaluate the efficacy of protopine alkaloids from Macleaya cordata (MPTA) against avian pathogenic Escherichia coli (APEC) in broilers.
Methods: Following intraperitoneal challenge with E. coli O78 in 300 10-day-old Lingnan yellow broilers, infected birds received 7-day oral treatments with either MPTA pulvis (MPTA-P) at clinically effective doses (400−1,600 mg/kg), 0.5% Siwei Chuanxinlian powder, or no treatment, alongside unchallenged controls.
Results: MPTA-P at 400 mg/kg significantly reduced mortality to 30% compared to 66.7% in infected controls (p < 0.05), while achieving 50% clinical recovery and significantly improved terminal body weight. Pathological analysis confirmed substantial mitigation of characteristic lesions, including hepatic congestion, fibrinous pericarditis, and intestinal hemorrhage. Higher doses (800−1,600 mg/kg) showed comparable mortality reduction (30%−36.7%) without additional benefits.
Conclusion: Dietary supplementation with 400 mg/kg MPTA-P for 7 days provides effective protection against APEC-induced mortality and organ damage, supporting its potential as an alternative to antibiotics.

Key words: Protopine total alkaloids; Macleaya cordata (Willd.) R. Br.; avian pathogenic Escherichia coli; chickens