Abstract
1. Tannic acid (TA) and chitosan (CH) are natural compounds with antioxidant, antimicrobial and immunomodulatory bioactivities. This study evaluated the effects of dietary TA, CH and their combination on White Pekin ducks aged 0 to 21 d.2. A total of 336 one-day-old Pekin ducks were randomly assigned to one of four dietary treatments with six replicate cages per treatment and 14 birds per cage. The treatments included a basal diet (CON), CON +0.2% TA, CON +0.2% CH and CON +0.2% TA + 0.2% CH. The trial lasted 21 d.3. Dietary supplementation with 0.2% TA alone increased average daily gain (p < 0.05), while 0.2% CH decreased thymus weight and thymus index (p < 0.05). Both TA and CH alone improved serum antioxidant status and immunoglobulin levels, but their combination did not give any synergistic effects.4. All supplemented diets modified caecal microbial community structure, which significantly reduced the relative abundance of Proteobacteria at the phylum level and Desulphovibrio at the genus level (p < 0.05).5. In conclusion, 0.2% TA alone improved growth performance, while 0.2% CH alone enhanced antioxidant and immune function in 0-21 d Pekin ducks. The combination of TA and CH showed no synergistic benefits. Both compounds beneficially modulated caecal microbiota by inhibiting potentially harmful taxa. These results indicated that single supplementation of TA or CH is more suitable for Pekin duck production.