Ammonia Emission from Group-housing Systems for Sows with Straw Bedding: Model Assessment

A model was developed as a tool for designing straw-bedded sow group-housing systems with low ammonia emission. The model calculates the total ammonia emission by integrating ammonia volatilization from all the urine pools in the house. A representative sow house with 60% straw bedding area, 14% drinking area (slatted floor with pit), 3% waiting area in front of electronic feeding stations (slatted floor with pit) and 23% alley (solid floor) was used for both model development and assessment.. Simulations were performed to elucidate the effect of the distribution of the urinations over the different surfaces, relating this to the size and distribution of the urine pools, and the area of the surfaces urinated upon. The results were compared with emission data collected during summer from a reference sow house. When urinations were distributed evenly over the four emitting surfaces the model estimated ammonia emissions as 11.7 g/d per sow, with 27%, 22%, 9% and 42% coming from the straw bed, the drinking area, the waiting area and the alley respectively. By comparison, the total measured emission from the house was 8.7 g/d per sow with 90% confidence interval 6.5-10.9 g/d. If the entire emitting area was assumed to be straw bedding, the calculated emission from the house was 5.8 g/d per sow. Assuming slatted and concrete floors without straw bedding increased the emission to 16.5 g/d per sow. It is concluded that measures to reduce the ammonia emission from the bedded sow house should be aimed at decreasing the emission from the solid floor and/or allowing more urinations on the straw bed.