Epidemiological studies on Salmonella in a certain area ("Walcheren Project") V. Studies into the possibility of fattening pigs free from Salmonella.

Studies performed some years ago showed that Salmonella-free pigs for slaughter could be produced under experimental conditions if a number of hygienic measures were taken, such as the purchase of Salmonella-free piglets, the use of properly pelletized feed, thorough cleaning and disinfecting of the pigsty and the prevention of all contamination from the surroundings. In this paper four trials are described which examined whether pigs could also be fattened free from Salmonella under practical conditions on the farm. For this purpose one pigsty on a Salmonella-contaminated farm was used, in which the aforementioned hygienic measures were taken. Despite all these precautions it proved impossible to obtain Salmonella-free pigs. In fact, in three of the four experiments a massive Salmonella infection became manifest among the pigs. The experiments revealed a number of ways in which contamination might have occurred. The existence of these routes of infection was caused by the fact that the measures described above were not carried out accurately, an indication that it will be very difficult to meet the hygiene requirements under farming conditions. Further experiments will have to ascertain whether this is generally the case. In the third and fourth trials, the investigations were not confined to the farm, but were also extended to the period of slaughtering. These made it clear that transportation as well as the waiting time in the slaughterhouse also provided many opportunities for contamination of the pigs, in spite of extensive cleaning and disinfecting of both the cattle-truck and the lairages.