Reduction of stocking density: effects on odour and ammonia emission?

The aim of this study was to determine the influence of stocking density on ammonia and odour emitted by growingfinishing pig units. This trial was conducted in our experimental farm in Romillé (35) involving two identical rooms. In the first room (noted D1,43), 60 pigs were divided in 6 pens of 10 pigs each (stocking density =1,43 pig per square meter)and in the second room (noted D1, only 42 pigs were divided in 6 pens of 7 pigs each (stocking density= 1 pig per square meter). Ambient parameters were continuously recorded during the period between pig entering and first departure for slaughtering. Ammonia and dust concentrations in the ambient air and ammonia and odour concentrations in the extracted air were measured each two weeks in both rooms. In our study, reduction of stocking density involves a decrease of dust concentration but has no effect on odour emission per pig. The most significant effect is measured on ammonia concentration in the ambiance and on ammonia emission per pig. In fact, reduction of pigs in the room leads to significantly increase ammonia in the ambiance and in the extracted air.