Impact of organic dairy cattle manure on environmental and egg microbiology of organic free-range layer flocks.

Authors: Garcia, Javier; ANDERSON, KENNETH - North Carolina A&t State University; Guard, Jean; Gast, Richard; Jones, Deana

Submitted to: Journal of Applied Poultry Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/22/2021
Publication Date: 12/1/2021
Citation: Garcia, J.S., Anderson, K., Guard, J.Y., Gast, R.K., Jones, D.R. 2021. Influence of sustainable grazing on environmental and egg microbiology of organic free-range layer flocks. Journal of Applied Poultry Research. https://doi.org/10.1016/j.japr.2021.100189.
DOI: https://doi.org/10.1016/j.japr.2021.100189

Interpretive Summary: Due to consumer demands, the popularity of free-range, and organic poultry has increased in the United States. However, little is known on how sustainable rotational grazing or pasture could influence the environmental and egg microbiology of organic free-range laying flocks. A study was conducted to evaluated if flocks in paddocks previously grazing by dairy cattle had changes in environmental and egg microbiology compared to flocks in pastures not exposed to cattle. Environmental and egg sampling occurred approximately 8 weeks for the occurrence of Listeria spp., Campylobacter spp., Salmonella spp., and levels of Enterobacteriaceae in flocks between 20 to 44 weeks of age. No differences in the occurrence of Listeria spp., Campylobacter spp., and Salmonella spp. were observed between the sustainable grazing and control grazing free-range flocks. The prevalence of total coliforms was greater in sustainable grazing flocks compared to control organic flocks. The time of year also influenced the microbial levels that were recovered from environmental and egg samples. Samples taken during the summer had the highest level of all populations observed. More research is needed to fully understand the environmental and egg microbiology of free-range, organic flocks.

Technical Abstract: The popularity of free-range, and organic poultry has increased in recent years due to consumer demands. A study was conducted to evaluate how sustainable rotational grazing could influence the environmental and egg microbiology of organic free-range laying flocks. Sister flock of brown egg layers were split and maintained in a rotational paddock grazing schedule that was either previously grazed by organic dairy cattle or had not been exposed to livestock. Environmental and egg sampling occurred approximately every 8 weeks between 20 to 44 wks of age for occurrence of Listeria spp., Campylobacter spp., Salmonella spp., and enumeration of Enterobacteriaceae. There were no significant differences in the occurrence of Listeria spp., Campylobacter spp. and Salmonella spp. in environmental and egg samples between sustainable and control grazing organic free-range flocks. A random sampling of Enterobacteriaceae colonies produced 211 viable isolates for biochemical identification. Seventeen genera, species, or serotypes were identified. There was a greater (P < 0.05) prevalence of total coliforms found on shell emulsion, egg contents, nest box straw and forage grass samples from sustainable grazing compared to control organic flocks. Season of the year impacted microbial levels recovered from environmental and egg samples, with summer having the highest level of all populations monitored. Additional studies are needed to fully understand the effect of sustainable rotational grazing on the prevalence of pathogens and Enterobacteriaceae on organic nest-run eggs and the grazing environment.