Evaluation of essential oils in beef cattle manure slurries and applications of select compounds to beef feedlot surfaces to control zoonotic pathogens

Authors: Wells, James - Jim; Berry, Elaine; GUERINI, M.N. - Former ARS Employee; Varel, Vincent

Submitted to: Journal of Applied Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/4/2014
Publication Date: 6/1/2015
Publication URL: http://handle.nal.usda.gov/10113/61575
Citation: Wells, J., Berry, E.D., Guerini, M., Varel, V.H. 2015. Evaluation of essential oils in beef cattle manure slurries and applications of select compounds to beef feedlot surfaces to control zoonotic pathogens. Journal of Applied Microbiology. 118;295-304.

Interpretive Summary: Animal manures are rich in bacteria and can be a source of odors and pathogens. Treatment of the manure can reduce these hazards. This study evaluated a variety of low cost antimicrobial compounds for ability to reduce odor and kill pathogen. Terpene alcohols are generated during wood and pulp processing, and these compounds have antimicrobial activities. All tested compounds were effective in reducing odor and pathogens in manure slurries prepared in the laboratory. Thymol is a terpene phenol extracted from plants and had been evaluated previously for odor and pathogen reductions in laboratory studies, but had not been fully studied in a beef production environment. Based on preliminary testing, three compounds were selected for application in beef feedlot pens. Thymol (0.2%) and pine oil (0.4%) were each effective at reducing coliforms and Escherichia coli O157:H7 in manure when applied directly on the feedlot surface. Feedlot application of natural compounds can reduce pathogens in the pen. This may provide a preharvest intervention to break pathogen-host cycles. However, benefits to reducing E. coli O157:H7 colonization in the animal and on the hide need to be evaluated.

Technical Abstract: Aims: To evaluate natural terpene compounds for antimicrobial activities and determine if these compounds could be used to control microbial activities and pathogens in production animal facilities. Methods and Results: Thymol, geraniol, glydox, linalool, pine oil, plinol, and terpineol were tested in laboratory studies for ability to control the production of odorous volatile fatty acid compounds and reduce pathogen levels in manure slurry preparations. Thymol is a terpene phenolic compound and was most effective for reducing fermentation products and pathogen levels, followed by the extracts linalool, pine oil, and terpineol, which are terpene alcohols. Select compounds thymol, linalool, and pine oil were further evaluated in two separate studies by applying the agents to feedlot surfaces in cattle pens. Feedlot surface material (FSM; manure and soil) was collected and analyzed for fermentation products, levels of coliforms and total Escherichia coli, and presence of E. coli O157:H7, Campylobacter, Salmonella, Listeria, and L. monocytogenes. The reduction in fermentation products but not pathogens was dependent on the moisture present in the FSM. Treatment with 2000 ppm thymol reduced the prevalence of E. coli O157:H7 but not Listeria. In a separate study, treatment with 4000 ppm pine oil reduced E. coli O157:H7, Listeria, and Campylobacter. Linalool was tested at two levels (2000 and 4000 ppm) and did not affect pathogen levels at either concentration. Conclusions: Natural compounds bearing terpenes can control pathogenic bacteria in treated manures and when applied to the feedlot surface in production cattle systems. Pine oil is a cheaper alternative to thymol and may be a useful treatment for controlling pathogens. Significance and Impact of the Study: The control of bacterial pathogens in animal productions systems is an important step in preharvest food safety. Waste products, such as pine oil extract, from the pulp wood industry may have application for treating feedlot pens and manures to reduce the pathogen load.