Livestock production significantly contributes to global environmental change. In particular, ammonia (NH 3) emissions from pig production contribute to soil acidification and water eutrophication. NH 3 volatilisation from animal housing and during effluent management are related to nitrogen (N) excretion in feces and urine. Previous studies have shown that reducing dietary protein content (20% vs 12%) is an efficient way to reduce N excretion and associated NH 3 emissions (Portejoie et al., 2004; Hayes et al., 2004; Leek et al., 2007). In this study, we explored pig feeding strategies with lower N content (10%) which can reduce ammonia emissions and nitrogen dispersion in the environment. We formulated diets with different content of crude protein (CP): 13% CP with 10% of soyabean meal (Control-diet) vs 11.5% of CP with 5% of soyabean meal (Intermediate-CP-diet) vs 10% of CP with no soyabean meal (Low-CP-diet). Experimental diets were balanced on their net energy content (9.51 MJ/kg) and on the amino acids /lysine ratio (methionine+cystine (60), threonine (65), tryptophan (20), isoleucine (60) and valine (70)) with an adequate supplying essential amino acids. A total of 36 Pietrain x (Large White x Landrace) entire males (mean body weight (BW): 45±10 kg) was used in this study (n=12 per experimental diet). Animals were housed individually in metabolism cages equipped for feed and water intake measurement and separated collection of feces and urine. All animals were adapted to experimental conditions, diets, and metabolism cages during 14 days. After the adaptation period, total slurry was collected per pig during 7 subsequent days. After the adaptation period, total feces and urine were collected separately per pig during 7 subsequent days. After this collection period, pigs were housed in climate respiration chambers (two pigs with their mixed feces and urine to mimic slurry in individual cage per chamber) for 6 d to measure feed and nutrient intake, digestibility of nutrients, nitrogen balance and NH 3 emissions from animal and slurry. We did not observe any effect of the experimental diets on the daily gain of animal: 764g/d with the Controldiet vs 774g/d with the Intermediate-CP-diet vs 703g/d with the Low-CP-diet (P < 0.05) or on the daily feed intake with an average of 179g/kg BW 0.6. The NH 3 emissions were higher in the Controldiet group, intermediate in the Intermediate-CP-diet group and lower in the Low-CP-diet group. Nitrogen balance calculations are in progress. A reduction of 3% of crude protein content in pig diet is an efficient way to reduce NH 3 emissions.