Ammonia emission from excreta of growing-finishing pigs as affected by dietary composition

Ammonia, volatilised from pig slurry decreases manure's fertiliser value. Furthermore, the deposition of ammonia emitted into the atmosphere may cause undesirable changes in aquatic and terrestrial ecosystems. At present, there is increasing interest in nutritional means to reduce ammonia emission.In pigs, nitrogen excreted via faeces is predominantly incorporated in bacterial protein, which is less susceptible to rapid decomposition. Nitrogen excreted via urine is mainly in the form of urea, which is easily converted into ammonia and carbon dioxide by the enzyme urease present in faeces.In different experiments the effect of dietary factors on nitrogen excretion of pigs and on pH as well as ammonia emission from slurry were investigated. Increasing the level of non-starch polysaccharides (NSP) in the diet shifted nitrogen excretion from urine to faeces and reduced slurry pH. The latter was caused by an increase of volatile fatty acid formation in faeces and slurry during storage. Lowering dietary electrolyte balance (dEB; Na + K - Cl) and adding acidifying Ca-salts: CaSO 4 , CaCl 2 or Ca-benzoate instead of CaCO 3 , a common added salt in commercial pig feed, reduced the pH of urine and slurry. Reducing dietary crude protein (CP) and supplementing essential amino acids decreased the total and urinary nitrogen excretion.These changes in dietary compositions, causing a lower urinary nitrogen excretion and pH of slurry, resulted in a strong reduction of ammonia emission from slurry. Changing dietary composition to reduce ammonia emission did not influence animal performance.It is concluded that manipulating the dietary factors such as NSP, dEB, Ca-salts, and CP, influences ammonia emission from slurry, while maintaining a normal pig performance. Such this approach might be an economic way to reduce the environmental impact of pig farming.