C.M. Groenestein

Effect of Feeding Schedule on Ammonia Emission from Individual and Group-housing Systems for Sows

The effect of feeding schedule on ammonia emission from housing systems for sows was studied. The hypothesis was that changing the feeding schedule would change the diurnal pattern of the ammonia emission and that daytime feeding would cause more ammonia to be emitted from the manure compared to evening feeding. The experimental units were an individual housing system with 64 dry sows in stalls (system A) and two group-housing systems: system B with 62 dry sows and feeding stalls and system C with 65 dry sows and electronic sow feeders (ESFs). In systems A and B, the sows were fed simultaneously twice daily. In system C, the sows were fed sequentially once a day. During feeding schedule 1, feeding times in systems A and B were 7:30 and 15:30 h, in system C feed was available from 15:30 h on. During schedule 2, feeding times in systems A and B were 7:30 and 21:30 h, in system C food was available from 7:30 h on. Ammonia emission, indoor temperature and animal activity were measured and the data were analysed considering autocorrelations with a time-series model. The values for the coefficients of determinations R2 of the models explaining ammonia emission by indoor temperature and animal activity were 48% for system A, 66% for system B and 64% for system C. In all three systems, the diurnal patterns of the indoor temperature, animal activity and ammonia emission changed considerably with the feeding schedule. Average ammonia emissions per sow for feeding schedules 1 and 2 were, respectively, 0·71 and 0·68 g h−1 (probability P=0·23) from system A, 0·60 and 0·61 g h−1 (P=0·75) from system B and 0·69 and 0·76 g h−1 (P<0·01) from system C. It can be concluded that changing the feeding schedule alters the diurnal pattern of the ammonia emission, but if the animals are fed simultaneously, changing the feeding time does not affect the total amount of ammonia emitted. However, with the animals fed sequentially, the ammonia emission falls by 10% if the feeding starts in the afternoon instead of in the morning.

Ammonia emission from individual- and group-housing systems for sows

Given that freedom of movement improves sows welfare, the implications for the emission of ammonia of keeping sows in groups instead of individually were investigated. Three housing systems were compared: System A, with 64 sows kept individually in feeding stalls with 2.8 m2 surface area per sow; System B, with 62 group-housed sows, free access stalls with 3.3 m2 surface area per sow; System C, with 65 group-housed sows, electronic sow feeders and with 3.4 m2 surface area per sow. The sows in Systems A and B were fed simultaneously twice a day at 7:30 and 15:30 h. In System C the sows were fed sequentially once a day from 15:30 h onwards. The study was carried out in winter during three one-week periods. Average outdoor temperature was 3.7 degrees C. The average ambient temperatures recorded in the houses were thermoneutral: 19.8 degrees C for System A, 19.2 degrees C for System B and 19.0 degrees C for System C. The average ammonia emission per sow was 0.72, 0.62 and 0.70 g hour-1 for the systems A, B and C, respectively. For the systems A, B and C this implied that 23, 20 and 23% of the nitrogen intake was emitted as ammonia nitrogen, respectively. The emission from System B was significantly less (P<0.05). The diurnal pattern of the ammonia emissions from Systems A and B were biphasic and were related to feeding times. In System C the diurnal pattern had a more monophasic course related to the feeding time in the afternoon with an additional small peak in the morning after the lights were switched on. The diurnal pattern of ammonia emission from sow houses was related to the feeding schedule. Under thermoneutral conditions, giving sows a larger area at their disposal - such as with group housing - did not imply an increase in ammonia emission.