Does rearing system (conventional vs. organic) affect ammonia emissions during the growing and fattening periods of pigs?

•Differences in growth performance between conventional and organic rearing system.•Differences in excretory behaviour between conventional and organic rearing system.•Differences in ammonia emission between conventional and organic rearing system.

Ammonia emissions from organic (ORG) and conventional (CON) rearing systems in relation to pig growth rate and behaviour were studied. Microclimatic conditions and ammonia concentrations were monitored. Excretory behaviour was recorded in the growing and fattening periods using video cameras. Throughout the experiment, significantly lower ammonia emission was detected in facilities of the ORG pigs (P < 0.001). The differences in ammonia emission may be partially explained as a consequence of lower level of crude protein, lower feed intake and different growth performance of ORG pigs. Urination and defecation indoor (on the slatted and solid floors) were higher in the CON group (P < 0.05). The results of the present study show that the minimum requirements specified in organic legislation are well suited to normal pig excretory behaviour in both growing and fattening stages and provides pigs cleaner indoor space as well as an improved environment for human and pigs, with around 40% of reduced ammonia emission.