Describing the Salmonella classification levels for low-volume production systems utilizing abattoir-based samples and classification stability over time

Results: In 2002, 934 of 14,401 samples (6.5%), and in 2004, 1639 of 13,718 samples (11.9%) were seropositive for Salmonella (ELISA sample-to-positive ratio ≥ 0.4). Average Salmonella seroprevalence in 2002 was 6.8%, median prevalence was 0.8%, and within-producer prevalence range was 0% to 59.2%. In 2004, average seroprevalence was 11.8%, median prevalence was 5.2%, and range was 0% to 81.8%. In 47% of low-volume production systems classified according to the Danish Salmonella classification system, classification did not change from 2002 to 2004. However, 53% of systems did change classification, with most moving to classifications representing higher observed seroprevalence.