The age of production system and previous Salmonella infections on-farm are risk factors for low-level Salmonella infections in laying hen flocks.

An explorative field study was carried out to determine risk factors for Salmonella infections in commercial laying hen flocks. For this purpose, 29 laying hen farms, including farms using conventional and alternative housing systems, were intensively sampled. An on-farm questionnaire was used to collect information on general management practices and specific characteristics of the sampled flock such as flock size, age of the hens, and age of the infrastructure. Salmonella was detected in laying hens from 6 of the 29 sampled farms. Using multivariate logistic regression with the Salmonella status of the flock as an outcome variable, a previous Salmonella contamination on the farm and the age of the production system were identified as risk factors for the presence of Salmonella in laying hens (P<0.05). The housing system did not have a significant influence on the prevalence of Salmonella in the current study.