Efficacy of a phytogenic feed additive on ammonia emissions of growing-finishing pigs Environmental pollution is one of the greatest challenges facing the world. In this regard, ammonia (NH 3) emissions from the livestock production sector play an important role. Aerial NH 3 negatively impacts the health of animals and farm workers, and it contributes to soil and water acidification. Pig production is responsible for a large proportion of these NH 3 emissions. Phytogenic feed additives (PFA) have improved feed efficiency, which helps reduce nitrogen excretion. In addition, specific plant bioactive compounds can exert a direct effect on manure to reduce NH 3 formation. The present study evaluated effects of a PFA on feed efficiency during all grower/finisher periods (11 weeks) and NH 3 emissions during the final two weeks of the finisher period. In this trial, eight climatic chambers (4 chambers per treatment, 3 pens × 3 animals) were used to allocate 72 barrows and female pigs to one of two treatment groups (Control or PFA). Zootechnical performance was measured per chamber. NH 3 emissions were measured by a photoacoustic gas monitor (INNOVA). Pigs fed diets containing PFA showed no significant differences in feed efficiency compared to the control group. However, the amount of NH 3 produced was significantly (P=0.01) reduced by 19.8% (from 17.95 to 14.40 g/animal/day). These findings suggest that the PFA used significantly reduces NH 3 formation and emission.