An experiment has been done with a group of 27 pigs fed (at 95% of ad-libitum) a 2 phase feeding program (growing (G) from 35 to 65 kg and finishing (F) from 65 to 95 kg) and 3 diet treatments were applied: low protein (G: 138.2g crude protein(CP)/kg feed and F: 131.0g/kg), medium protein (G: 161.2g/kg and F: 139.9/kg) and high protein (G: 208.4g/kg and F: 189.2g/kg). Lysine was incorporated in the diet. A nitrogen (N) balance was done to determine the N retained as lean tissues and the N excreted and analysis was realized on 10 components of the odor emission from the slurry to verify the effect of the treatment on variation of their concentration. The conclusions of this experiment are that: 40% less N was found in the slurry produce by growing and finishing pigs on the reduce CP diets compare to the high CP diet treatment; the concentration of the odorant components of the odor emissions decreased with the reduction of the CP in the diet; maximum lean tissue deposition is obtained with lowering the CP with an ideal balance of the essential amino acids(EAA).

The lower N level in the slurry obtained when reducing the CP level in the diet is interesting considering that the diet is balanced to maintain the EAA and allows a maximum lean tissues retention. The effect on certain components of the odor emissions can also be measured but unless olfactometric analysis of those emissions are done the reduction of certain components may not result in a lower odor intensity of on a better hedonic tone of the odorant.