Dynamics of Salmonella Shedding and Welfare of Hens in Free-Range Egg Production Systems.

The current study investigated the effect of environmental stressors (i.e., weather changes) on shedding in free-range production systems and the correlations with behavioral and physiological measures (i.e., fecal glucocorticoid metabolites). This involved longitudinal and point-in-time surveys of shedding and environmental contamination on four commercial free-range layer farms. The shedding of was variable across free-range farms and in different seasons. There was no significant effect of season on the prevalence during this investigation. In this study, the combined most probable number (MPN) counts in environmental (including feces, egg belt, dust, nest box, and ramp) samples were highest in samples collected during the summer season (4th sampling, performed in February). The predominant serovars isolated during this study were serovar Mbandaka and serovar Typhimurium phage types 135 and 135a. These two phage types were involved in several egg product-related outbreaks in humans. Multilocus variable-number tandem-repeat analysis (MLVA) results indicated that MLVA types detected from human food poisoning cases exhibited MLVA patterns similar to the strains isolated during this study. All isolates ( 209) were tested for 15 different genes involved in adhesion, invasion, and survival of spp. We also observed variations for , , and There were no positive correlations between fecal corticosterone metabolite (FCM) and prevalence and/or shedding in feces. Also, there were no positive correlations between prevalence and count (log MPN) and any of the other welfare parameters. In this study, the welfare of laying hens and shedding were compared over a prolonged period of time in field conditions. This study investigated the long-term shedding of serovars in a free-range egg production system. Given that there is increasing demand for free-range eggs, it is essential to understand the risks associated with such a production system.