Development of a mobile organic piggery for outdoor pork production – function, productivity, animal behaviour and environmental risk assessments

Pens in outdoor pig systems in general become permanent during the grazing period. The excretion behaviour of the pigs creates plant nutrient hotspots within pens. In this study we developed a mobile organic piggery (MOP) without electric fencing that can be moved to a new grazing area each day. The aims were to distribute plant nutrients evenly, provide the pigs with continuous access to fresh herbage, and improve productivity and the working environment. Initially, 25 fattening piglets were installed in the MOP on a clover/grass ley. Nitrogen, P and K flows to and from the MOP were monitored during 87 days. The purchased feed included 80% of the energy norm for pigs in indoor systems and the pigs were automatically fed. The MOP was moved 65 times. Behavioural studies including excretion behaviour were conducted during a two-week period. Net nutrient accumulation was 88 kg N, 31 kg P and 10 kg K ha-1 for the total grazing area (4212 m2). Average liveweight gain was 675 g day-1. Average feed conversion rate was 2.7 kg feed kg-1 liveweight gain. The pigs grazed, on average, almost half the day. With the MOP system it was possible to use a lower quality concentrate feed in terms of energy and protein supply in combination with regular access to fresh herbage. The MOP system also allowed a more even distribution of animal manure within the total grazing area, compared with permanent pens. Avoiding harmful point loads of nutrients decrease the risk of nutrient losses