All types of pig populations in Danish pig production are monitored for salmonella. The surveillance ensures that the occurrence of salmonella will remain at a low level in Danish pork. The surveillance of salmonella is risk-based in order to guarantee that pig populations with previous outbreaks of salmonella are monitored very carefully.

Abattoirs monitor the occurrence of salmonella in the pigsties
Slaughter pig populations are monitored by means of meat juice samples taken by the abattoir. The meat juice sample is examined for antibodies against salmonella and based on the meat juice samples, a slaughter index is calculated. Populations with an index above 65, are assigned level 3. Pigs from these populations must be slaughtered separately with increased hygienic monitoring or slaughtered with subsequently washing with hot water (VVS).
Populations with an index between 40 and 65, are assigned level 2.
Slaughter pigs at levels 2 or 3 are paid at a lower price.

Between 1 and 1.5 per cent of the pig population is at level 3, and 2 to 3 per cent of the pig population is at level 2.

Relevant links:
SEGES, the Knowledge Centre for Pig Production  
The Danish Veterinary and Food Administration