[Lowering of the nitrogen excretion in swine]

Because of the low efficiency of N utilisation, animal husbandry is the main contributor of N pollution into environment within agricultural production systems. Possible solutions are to regulate the fertilizing and animal stocking rate per hectare as well as improving the efficiency of N utilisation in animal nutrition. Production of pig manure is determined by the kind of animal production, feeding level, performance level and N intake. Increasing performance improves nutrient utilisation which in turn reduces the amount of manure and manure-N per production unit. N intake especially influences N excretion. Therefore feeding in exact relation to the requirement is most important for an ecological pig husbandry. The proportion of the easily soluble urinary N to faecal N can be lowered by diet composition, mainly by higher amounts of bacterial fermentable substances. Thereby the ecological quality of manure is improved. Lowering of excessive N excretion in pigs via feeding measures is possible in two ways, (1) by exact adaptation of the protein supply in agreement with the changing requirements and (2) by improving the dietary amino acid balance. In the first case N excretion in fattening pigs and sows can be reduced up to 12%. In the second case lowering dietary protein and supplementation with crystalline amino acids diminished N emission up to 40% to 50%, practically achievable are under present conditions about 20%.