Abstract: This study evaluated the impact of a mixed feed additive containing benzoic acid, saponin, prebiotics, and minerals on odor emission during pig manure storage in slurry pits. The treatment group was fed a diet supplemented with 0.5% of the additive. NH3 emissions were approximately 1.8 times higher in the treatment group compared to the control group, and sulfur compound emissions also tended to be higher in the treatment group than in the control group (p>0.05). Despite the known odor-reducing properties of benzoic acid and saponin, this study did not observe a reduction in NH3 or H2S. The low inclusion rate of benzoic acid (0.2%) likely hindered its efficacy. The impact of saponin on gut microbiota and odor reduction may be time-dependent, typically taking around 40 days for significant effects. Manure samples were collected within 20 days of supplementation in this study, so the microbial community may not have had sufficient time to adapt and decrease gaseous emissions.