1. Corni fructus is the fruit of Cornus officinalis, a dogwood species. This study was conducted to prepare fermented corni fructus preparation (FCFP) and fermented kelp (FK) from corni fructus and by-products of Laminaria japonica fermented with Bacillus subtilis and Aspergillus oryzae. 2. The effects of dietary FCFP and FK as replacer of oxytetracycline (OTC) on growth performance, meat composition, meat oxidative stability, and emissions of ammonia (NH3) and hydrogen sulphide (H2S) from broiler chicken droppings were investigated. 3. A total of 140 d-old broiler chicks were randomly allotted to 4 dietary treatments including control, OTC (0.05 g/kg), FCFP (5 g/kg), and FK (5 g/kg). 4. Overall, inclusion of FCFP resulted in lower weight gain and feed intake during the overall experimental period. Broilers fed FCFP diets tended to have lower crude fat and higher crude ash content in the carcasses. 5. In the fresh state, the malondialdehyde (MDA) value of broiler meat was lower in the FK supplemented group. At one week, meat from broilers fed antibiotic and FK diets had lower MDA values, whereas at 2 weeks broiler meat from all dietary treatment groups had lower MDA values than the control. 6. Dietary supplementation with FK significantly reduced faecal NH3 emissions throughout the experimental period, whereas dietary OTC and FCFP supplementation increased NH3 emissions at 2 and 4 weeks. There were no significant effects of dietary treatments on H2S emissions throughout the experimental period, except during week one, when FCFP supplementation reduced the emission. 7. In conclusion, dietary supplementation with 5 g/kg FK improved the oxidative stability of broiler meat and reduce faecal NH3 emissions without affecting growth performance.