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On a farrow-to-finish pig farm, Salmonella prevalence was monitored depending on time and site aiming to overview of a complete fattening period. Sampling was conducted from November 2009 to April 2010 at intervals of 14 days and included stables, the environment, farm equipment as well as the staff in charge of the animals.
During the second part of the sampling period, Nll. jejunales from six shipments of finisher pigs were investigated. Using the records, the animals were associated to the fattening units. Suspicious subcultures were isolated and serotyped. In the end, prevalence profiles along pre-fattening and finishing period as well as carcasses from three fattening units were available. The Salmonella prevalence varied between 5.3 % and 21.2 %, with an average of 10.0 %. Only the monophasic variants of Salmonella Typhimurium with the antigenic structure 4,5,12:i:- and 4,12:i:- as well as the biphasic variants of Salmonella Typhimurium with the antigenic structure 4,5,12:i:1,2 and 4,12:i:1,2 were found. While the monophasic variances were obtained along the entire sampling period, the biphasic variants emerged in the second half of the sampling period, with different percentage at every sampling occasion.
4.0 % of the samples taken from the environment were Salmonella positiv. Within the sow area no sample was Salmonella positiv during the entire sampling period. 1.7 % of the samples taken in the farrowing area contained Salmonella, the highest proportion of positive samples was found in samples from the pre-fattening area (29.7 %). In the fattening area, a prevalence of 15.8 % was obtained. Samples taken from the farm staff were Salmonella negativ. Of the six shipments sent to slaughter, 5.9 % to 43.8 % of the lymph nodes were Salmonella positive, on average, 26.3 % were positive. Parallel with the other samples, the serotypes were different. A broad spectrum of variants was found in the three units which were monitored during prefattening and fattening. Lymph node examinations of two fattening units revealed a variant of Salmonella Typhimurium which had not been found in those units previously. A general prevalence of Salmonella on this farm was obtained.
When compared to the prefattening period, lymph node examinations revealed a large percentage of fattening pigs as Salmonella carriers. There is a constant risk of a Salmonella reentry. Therefore, every regrouping poses a risk of potential transfer.
• A low sampling frequency and a few number of samples taken, may lead to a false
estimation of Salmonella prevalence.
• Microbiological investigations of randomly collected samples at one sampling occasion
or of samples taken from single fattening units do not allow a general conclusion
concerning the Salmonella load of all fattening pigs.