Ammonia and nitrous oxide emissions for finishing pigs breeded on straw litter

The nitrogen loss in straw-based pig-on-litter systems is higher than in slatted-floor systems but the ammonia and nitrous oxide emissions are not well-known. Moreover, the effect of animal density on emissions has been little studied. Our objective was to evaluate ammonia and nitrous oxide emissions during pig breeding. Ammonia and nitrous oxide emissions were measured between 2001 and 2003 for over six hundreds of pigs, in experimental and commercial pig buildings, in winter and summer. Two measurement methods were used, the first one based on assumptions of animal and litter heat production, the second one based on a tracer gas. The tracer method confirmed the results of the simplified method provided the heat production of the litter is taken into account. The animal density effect is weak between 1.0 and 1.4 m2/pig but high at 2.6 m2/pig. At this low density, we observed an emission reduction during winter. We propose to use an ammonia emission factor between 15 and 25 % of excreted nitrogen for pigs breeded on litter with an input between 50 and 80 kg straw/pig during at least ten weeks. This factor reduces when the litter surface is above 2 m2/pig (5-15%), when the straw input increases or when the duration reduces. Nitrous oxide emissions were close to the half of ammonia emissions.