Beneficial effects of dietary green tea extract supplementation during necrotic enteritis challenge in broiler chicks

Necrotic enteritis (NE), an important enteric disease in poultry, is primarily caused by Clostridium perfringens, a Gram-positive anaerobe. This study evaluated the efficacy of different dietary inclusion levels of polyphenol-rich green tea extracts (GTE) in mitigating adverse effects of NE in broiler chicks. In a 28-day trial, day-old Ross 708 male broiler chicks (600) were randomly assigned to six dietary treatment groups, each consisting of five replicates with 20 birds per pen in a completely randomized design. All birds were fed a corn-soybean meal-based diet. The experiment included an unchallenged control (CON), challenged control (ACON), an antibiotic group (ABMD; 55 mg/kg Bacitracin Methylene Disalicylate), and three GTE-supplemented groups (250, 500, 1000 mg/kg; AGTX, AGTY, AGTZ). All but CON received a high-dose coccidia vaccine on day 13 and Clostridium perfringens challenge on days 18-19; CON received sterile broth. Growth performance and mortality were monitored weekly. On days 20 and 26, two birds per pen were necropsied for NE lesion scoring, serum nitric oxide quantification, and jejunal mRNA expression analysis of inflammatory cytokines and tight junction-related genes. Data was analyzed using SAS software, with statistical significance set at P ≤ 0.05. GTE supplementation reduced intestinal lesion scores and serum nitric oxide concentrations relative to ACON and upregulated the expression of ZO1, ZO2, and CLDN1 at both sampling time points. AGTX and AGTY treatments increased OCLDN expression on both days, whereas CLDN3 expression was elevated only on day 20. Although NE challenge induced a pro-inflammatory response, GTE supplementation enhanced ANXA1 expression, suppressed NF-κB during peak infection, and increased iNOS expression by day 26. Both GTE- and antibiotic-supplemented birds exhibited improved feed conversion ratio compared with ACON, with AGTX achieving the greatest body weight gain among challenged treatments, whereas AGTZ (1000 mg/kg) showed the poorest performance. Overall, dietary GTE supplementation at levels up to 500 mg/kg mitigated NE-induced growth suppression, improved intestinal barrier integrity, and elicited responses comparable to those of antibiotic growth promoters, supporting its potential as an alternative to in-feed antibiotics in broiler diet.