Analysis Of Factors Affecting Ammonia And Methane Emissions From Pig Slurries: Slurry Composition And Dietary Factors
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Cita bibliográficaAntezana, W., Cerisuelo, A., Estellés, F. & Calvet, S. (2018). Analysis Of Factors Affecting Ammonia And Methane Emissions From Pig Slurries: Slurry Composition And Dietary Factors. Proceedings of the European Conference on Agricultural Engineering (AgEng2018), 817-823.
Reducing crude protein is a recommended technique to reduce nitrogen excretion and ammonia emissions. Greenhouse gas emissions from slurry are also affected by nutrient composition. However, there are interactions among nutrients in feeds still not clarified. The objective of this study was to evaluate the impacts of different diets on nitrogen (N) and energy balances. A total of 13 diets were evaluated in digestibility trials using 78 animals. Diets were formulated to fulfil commercial standards, although differing in ingredient composition. Nutrient intake, excretion and potential NH3 and CH4 (Biochemical methane potential) emissions from slurry were measured. Animal weight was also monitored. Correlations between emissions and nutrient balance components were done. An analysis of variance was conducted to assess differences in nutrient balance of low, medium and high emitting animals, expressing animals per kg of live weight increased. For the N balance, a two-fold range in faeces to urine N excretion ratio was found throughout the experiments, even considering the low crude protein variations (from 15 to 16%). This was related to the ammonia emissions from slurry (r = -0.60, p<0.001). In fact, the amount of crude protein ingested to increase 1 kg of metabolic weight was positively correlated with the associated emissions (r=0.58, p<0.001). However, this was more related to the consumption by the animal than to the crude protein, which was relatively stable among diets. The difference between animals associated with high or low NH3 emissions per weight gain was therefore related to urine losses due to excess N intake. The energy balance shows that methane potential from slurry was mainly related to the excretion of indigested feed components, mainly the fibrous fraction (particularly the soluble fibre). It was clear that animals emitting high amounts of methane were those with higher dry matter and energy ingestion. The results of this study demonstrate relevant effects on N and energy balances at diets formulated according to commercial standards.