Nitrogen mass balance in deep litter during the pig fattening cycle and during composting

For welfare reasons, fattening pigs on organic farms are raised on deep lit ter in the open with simple, flexible climate tents for shelter. Within thi s system, the nitrogen (N) flow both during fattening of the pigs from 17 t o 100 kg liveweight in winter and during composting of the deep litter from the enclosures in summer was studied. During the fattening period, the pig s were provided with barley straw at four daily rates (0.67, 1.21, 1.32 and 1.87 kg) per kg increase in liveweight. During the summer period, N balanc es from four enclosures receiving straw at around the 1.32 kg rate were exa mined. Temperatures in the deep litter mat and in the compost heap were det ermined. as well as concentrations of ammonia (NH3) and nitrous oxide (N2O) in the compost heaps. The temperature increased after 4 weeks to between 4 0 and 70 degreesC in the deep litter mats receiving > 1.21 kg straw; the hi ghest temperatures were observed in the mats with the highest straw rate. T emperatures exceeded 50 degreesC in all compost heaps. In the deep litter m ars and compost heaps the highest temperatures were recorded for the longes t periods in the material containing the most straw. The initial concentrat ion of NH3 in the gas phase of the compost heaps was > 10 mg NH3-N/m(3), wh ich dropped to zero within 1 month. After the NH3 concentration had fallen, the amount of N2O increased significantly for a period in the two heaps wi th 1.21 and 1.32 kg straw. Over 120 days in summer, an average of 16.3 +/- 6 % N was lost from the four enclosures strawed at a rate of 1.32 kg (+/- 0 .2 kg) straw per kg increase in liveweight. During the winter 12-24 % of th e N excreted was lost during a fattening period of 119-134 days, and 15-42 % of the N stored was lost during the following composting period of 143 da ys. In total? 29-54 % of the N added to the deep litter mat in excretion an d straw was lost during the fattening period (119-134 days) and subsequent storage (143 days). The lowest loss was recorded from deep litter strawed d aily with 1.32 kg straw per kg increase in pig liveweight.