Gaseous emissions from fattening pigs offered an ad libitum high-fibre diet and kept on fully slatted floor: preliminary results

According to the literature, the diet composition of livestock can influence polluting gas emissions from agriculture. The aim of this preliminary study was to measure gaseous emissions from fattening pigs offered an ad libitum high-fibre diet (HFD) and kept on fully slatted floor. A batch of 24 fattening pigs was divided into two homogeneous groups randomly allocated to a treatment: conventional cereals-based diet or sugar beet pulpbased diet (HFD). With HFD, a significant decrease of animal performance was observed (837 vs. 962 g for the average daily gain). With pigs offered HFD, gaseous emissions per pig were significantly lower for NH3 (-30%, 6.64 vs. 9.47 g/d; P<0.05) and significantly greater for CH4 (+40%, 6.46 vs. 4.60 g/d; P<0.05). The emissions of N2O (0.34 g/d), CO2equivalent (0.27 kg/d), CO2 (1.68 kg/d) were not significantly influenced by the diet. Due to a more important microbial activity with HFD, the lower NH3-emissions could be attributed to the shift of a part of excreted nitrogen from urine (as urea) to faeces (as protein form), and to a lower slurry pH explained
by the increase of volatile fatty acid content. The higher CH4-emissions could be explained by a greater production in the digestive tract and in the slurry due to fibre fermentations. In conclusion, HFD allowed decreasing NH3- and increasing CH4-emissions. However, in terms of climate change, this increase was offset by the decrease of indirect N2O-emissions due to NH3-emission decrease, as indicated by the similar CO2equivalent-emissions in the two groups.