This research aims at analysing the economic effects of the European Union’s Nitrates Directive implementation on some representative dairy farms in Italy, using a mathematical programming model. The representative farms considered are located in Emilia-Romagna and Lombardia, which are potentially most affected by the Directive given their high livestock density. The study simulates two different farm response scenarios to the Directive. Simulation results show the importance of the creation and use of a manure market to dispose nitrogen from livestock surpluses in order to reduce the negative effects of the Directive on farm income. The herd reduction option is unfavourable, as it causes much larger income drop, which, for some farms, reaches one third of their income.