Epsilon Archive for Student Projects

Abstract

In organic animal production, synthetic amino acids are not allowed. Therefore, a higher level of crude protein is needed in the diet to pigs, which lead to more nitrogen (N) excreted in the faeces and urine. N can be emitted to the air in the form of e.g. ammonia (NH3), which contributes to eutrophication and acidification and as nitrous oxide (N2O), which is a very potent greenhouse gas. The emission of N can be reduced by e.g. modifying the diet and by reducing the defecated areas in the pens. The aim of this study was to enrich the outdoor yard in organic pig production with a rooting area filled with peat, and thereby also reduce the emissions of N. The hypothesis was that pigs avoid to dung in areas with high activity, and a rooting area should therefore direct the pigs to dung in a smaller area outside the rooting area. Peat is appreciated as a rooting material by pigs and it has a high potential to bind N, which reduces the emission of NH3. The complex environment (aerobic and anaerobic) that can occur in peat is not always optimal, which can lead to more N emitted as N2O.
The study was performed in a stable for organic finishing pigs in Skåne (the most southern part of Sweden). The stable consists of 8 pens, each dimensioned for 16 pigs. Two batches of pigs were studied. Studies of the pigs’ behaviour, measures of the emission of NH3 and hygiene of the floor in the outdoor yards were included. Furthermore, as a pilot trial in batch 2, the concentration of N2O was measured in closed chambers with two different methods.
The results showed that the pigs chose to stay outdoor and to lie outdoor to a higher extent when the climate was warmer (batch 2). During batch 1, the hygiene was poorer than in batch 2, but the emission of NH3 was observed to be lower. The explanation for this result is that the temperature in batch 1 was lower than in batch 2. The rooting area did not stimulate the pigs to root more or be more active, but the pigs directed their rooting to be more frequent outside, and a tendency (p=0.097) that the pigs chose to stay outside more was observed (Table 8,9,10 and 11). The pigs avoided to dung in the rooting area, and their dunging was mostly concentrated to the dunging area (area C), a result that corresponds to the hypothesis. This behaviour led to better hygiene in the outdoor yard and a lower emission of NH3 from the rooting area (49.9 mg/m2h) compared to the same area in boxes without rooting area (108.6 mg/m2h). However, from the dunging area (area C), higher emission of NH3 was detected in pens with the rooting area (134.8 mg/m2h) compared to boxes without it (80.1 mg/m2h) (Table 12 and 13). Because of the few measures of the concentration of N2O, conclusions can not really be made. Though, the measures showed altered concentrations of N2O (= emission) from outdoor yards with a rooting area, compared to outdoor areas without rooting areas, where no altered concentrations was detected (Figure 12-15).
The rooting area can be considered positive for the welfare of the pigs since it was popular both for rooting and as a lying area, and it resulted in a better utilization of all areas in the pen. Though, the higher emission of NH3 from area C and the detected emission of N2O from outdoor yards with a rooting area, concludes that more actions than a rooting area are needed to reduce the total emissions of N from outdoor yards. Suggestions for other actions are more frequent cleaning (which is facilitated by concentrated dunging), another type of dunging system and maybe another rooting material or another kind of peat. To reduce the total emissions of N from dung, it is important to take into consideration both NH3 and N2O in future studies.