Location: Egg Safety and Quality
Title: Pathogen Prevalence From Traditional Cage and Free Range Production Authors
Submitted to: National Egg Regulatory Officials Annual Meeting
Publication Type: Proceedings
Publication Acceptance Date: March 4, 2012
Publication Date: March 4, 2012
Citation: Jones, D.R., Anderson, K., Guard, J.Y. 2012. Pathogen Prevalence From Traditional Cage and Free Range Production. National Egg Regulatory Officials Annual Meeting. p.68-70. Technical Abstract: Overview: A study was conducted to determine if differences in pathogen prevalence occurred between a sister flock of conventional cage and free range laying hens. Both environmental and egg microbiology was monitored throughout 20 – 79 weeks of age. Salmonella, Campylobacter, and Listeria prevalence was monitored. Trends in prevalence for each pathogen varied dependent on season of the year and housing system. More research is needed before clear outcomes can be determined. Materials and Methods: A single strain of brown egg layers was utilized for this study. All birds were hatched and reared together. At 12 wks of age, free-range pullets were moved from floor pens to the range huts and paddocks. Conventional cage pullets were maintained in quad-deck rearing cages until approximately 16 wks of age when they were moved to the laying house. Both flocks received the same diet and lighting program (supplemental lighting provided in the range hut). The conventional cage and free range production facilities were located on the same research farm. Approximately every 6 wks, from 20 – 79 weeks of age, eggs and environmental samples were collected from both production systems. Free range floor eggs were cultured separately than nest box eggs. Environmental swabs were taken by moistening sterile gauze with sterile phosphate buffered saline and aseptically wiping the cage or nest box sections which held the eggs. Free range grass samples were aseptically collected by grasping a handful of grass from the paddock area and using sterile shears, cutting the grass approximately 2.5 cm from the ground. All samples were placed in sterile laboratory bags and transported to the laboratory on ice. Eggs and environmental samples were stored overnight at 4C before culturing was initiated. Environmental samples were collected in triplicate. Thirty eggs from each treatment (conventional cage, free range nest box, free range floor) were collected. Diluent was added to environmental swabs and grass samples. All samples were stomacher blended for one minute. For each treatment, six pools of three eggs were formed (24 eggs intact eggs per treatment). Each egg was aseptically cracked and contents collected. Shells were then rinsed with sterile phosphate buffered saline and macerated with sterile phosphate buffered saline. All shell and egg contents pools were assessed for Salmonella, Campylobacter, and Listeria according to our common laboratory practices. Results: Campylobacter was detected in each season, except spring. The greatest incidence of Campylobacter was found in free range nest box swabs. There was an issue when hens sitting and defecating in the nest boxes, therefore, it is not surprising to have a higher prevalence of Campylobacter. No egg contents pools were found to contain Campylobacter. In total, Campylobacter was isolated from 12 egg shell and environmental samples. There was a significantly greater prevalence of Campylobacter in the free range nest box environment compared to conventional cage and free range grass. Listeria was cultured from 7 egg shell and environmental samples. No egg contents were found to contain Listeria. At least one positive Listeria sample was detected each season. The greatest number (three) of positive samples was found in fall. Six of the isolates were associated with free range egg production. Four of the free range isolates were from the environment (nest box swabs – 2; grass – 2) and two were from free range floor egg shell emulsions. All isolates detected were L. innocua. There was no significant difference in Listeria prevalence amongst treatments. Salmonella was detected in all production environments and in every season. Additionally, Salmonella was detected multiple times in egg contents pools from all sampling environments (conventional cage – 2; free range nest box – 3; free range floor – 2). The greatest number of Salmonella positive shell emulsion pools came from the conventional cage (n = 4), then free range floor (n = 3). No Salmonella was detected in free range nest box shell emulsion pools. The conventional cage swabs had the greatest prevalence of Salmonella (n = 5). Previous research has noted that Salmonella is more easily cultured from dust than other environmental samples. The conventional cage production environment was dustier than the free range environment. Of the 21 Salmonella isolates detected during the study, 18 were S. Typhimurium, one S. Javiana (free range floor shell emulsion), one S. Enteritidis (free range grass), and one PCR failure (not stereotyped). There was no significant difference amongst treatments for the prevalence of Salmonella. In conclusion, the presence of fecal material in the nest box appears to contribute to the incidence of Campylobacter. Management practices and equipment should be designed to reduce the likelihood of hen defecation in nest boxes. Within the parameters of the current study, season of the year appears to affect pathogen detection. Additional research is needed for greater understanding of the impacts of various production systems on pathogen prevalence in the production environment, as well as associated with the eggs. The authors would like to acknowledge the contributions of Patsy Mason, Victoria Broussard, Otis Freeman, Tod Steward, and the staff of the NC Department of Agriculture and Consumer Services Piedmont Research Station. Without their assistance, this research would not have been possible. The peer-review publication of this research will be available in Poultry Science, March 2012.