In Europe, farmers are permitted to raise up to about 2
livestock units per hectare (Burton and Turner, 2003),
whereas in Denmark only 1.4 livestock units are allowed
per hectare of cultivated land (equivalent to 140 kg N/
ha) (Anonymous, 2006a). The extremely high pig
densities observed in Northern Vietnam are the result
of a lack of regulations for pig production. The result
indicates that authorities should improve environmental
regulations and specify the target objectives taking into
account existing practices and perceptions of stakeholders
affected by the livestock production (Pophyre
and Medoc, 2006).