Can on-farm serology predict the risk of Salmonella shedding at slaughter in fattening pigs?

Abstract

The objective of this study was to assess whether on-farm serology and other farm characteristics could be used as predictors of Salmonella shedding at the abattoir. For that, 1,500 pigs from 30 pig fattening units were selected. One month before slaughter, 50 pigs from each pig unit were tagged and bled for the detection of antibodies against Salmonella. Pooled floor fecal (PFF) samples from 10 pens were also collected for Salmonella detection in each pig unit. At the slaughter, colon content of each pig was collected for Salmonella shedding detection. Salmonella was present in 13 (43.3%) of the farms. Mean herd seroprevalence (OD%≥40) was 31.7% (95%CI= 21.8-41.0). A total of 316 pigs (23.6%) shed Salmonella at slaughter. A random-effects logistic regression analysis showed that serology, the percentage of Salmonella-positive pens on the farm, and the internal biosecurity score predicted reasonably well (Area under the curve -AUC-= 0.76; P<0.05) whether a pig would shed Salmonella at slaughter or not, with estimates of sensitivity (Se) and specificity (Sp) of 71.6% and 73.6%, respectively.