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United States Department of Agriculture

Agricultural Research Service

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Research Project: Understanding the Role of Commensal Anaerobic Bacteria in Odor, Emissions, and Antibiotic Resistance from Stored Livestock Manure

Location: Bioenergy Research Unit

2011 Annual Report


1a.Objectives (from AD-416)
Objective 1: Develop methods to reduce metabolic activity of microorganisms present in stored swine manure to decrease odor and gaseous emissions during storage. Objective 2: Characterize bacterial antibiotic resistance in swine feces and stored manure and potential for movement of resistance genes between bacterial species. Objective 3: Determine impact of natural plant compounds and/or their gut derived metabolites (e.g., tannins, pheophorbide, diterpenes) on levels of antibiotic resistance in commensal bacteria present in stored swine manure.


1b.Approach (from AD-416)
Intensification of modern livestock operations has resulted in the concentration of greater numbers of animals into fewer and fewer operations. This trend has also led to the inevitable concentration of manure generated by these facilities into increasingly smaller locations. In the Midwest, deep pit storage is the predominant method used to handle swine manure and this manure is a valuable renewable resource for use as fertilizer. However, concentration of manure has been accompanied by increased public concern about environmental impacts and public health. These include real and perceived fears of the effects of odors, volatile greenhouse emissions, and potential spread of antibiotic resistant microorganisms and genes. Therefore, research is needed to target the common factor relating these various concerns. This factor is the bacteria populations naturally found in manure and its precursor, animal feces. These bacteria are generally termed the commensal bacteria found in these two ecosystems (feces and manure). As a continuation of previous research in our laboratories, both classic microbiological methods as well as modern molecular biological approaches (i.e., direct 16S rDNA sequencing, quantitative real-time polymerase chain reaction (qRT-PCR)) will allow us to investigate the bacterial basis for production of odorous compounds, greenhouse gases such as methane, and the impact of using antibiotics in feed as growth promotants on antibiotic resistance present in the commensal bacterial populations. Research will be directed towards developing methods to reduce production of odors and emissions, identifying levels of antibiotic resistance in pure cultures, and identifying and quantitating resistance genes present in the manure. The potential for movement of such resistance genes between commensal bacteria and potential pathogens will also be investigated.


3.Progress Report
In 2011, research continued on studying the inhibitory effects of tannins on production of total gas and the odorous compound hydrogen sulfide from manure slurry under laboratory conditions. Tannins were chemically fractionated into larger and smaller molecular sizes to further delineate the active inhibitory components of the tannins. Initial experiments suggested that the lower size material was still inhibitory, and further dissection of this material will be carried out. Collaborative research was continued with Michigan State University on the combined effects of tannins and borax on inhibiting emissions from swine manure. This research applied molecular techniques to quantify the number of bacteria responsible for production of hydrogen sulfide and the effects of condensed tannins and borax on these bacterial populations. In collaboration with the Institute of Food Research, Norwich, United Kingdom, research was also continued on targeting expression of therapeutic proteins in the human gastrointestinal tract by genetically modified bacteria. Collaborators in the United Kingdom have extended this research into new areas and have received a grant from the Bill Gates Foundation for the production of polio virus vaccine. These results were communicated to the scientific community via presentations at domestic/international meetings and scientific publications.


4.Accomplishments
1. Combining condensed tannins and borax can reduce production of emission and odors from swine manure. Reducing production of greenhouse gases and odorous compounds such as hydrogen sulfide is an important goal for large-scale swine production operations. Condensed tannins, which are complex phenolic compounds naturally found in plants and trees, were studied for their abilities to inhibit bacteria present in stored manure. A collaboration of Agricultural Research Service (ARS) Bioenergy Research Unit scientists at the National Center for Agricultural Utilization Research (NCAUR), Peoria, IL, and Michigan State University have demonstrated that tannins isolated from the quebracho tree in South America, in combination with borax, will reduce overall gas and hydrogen sulfide production from manure slurries studied in the laboratory. These results can now be applied towards reducing odors and greenhouse gas emissions from large-scale swine facilities. Such reductions are of great interest to swine producers, environmental protection agencies, and local residents that live near swine facilities.


Review Publications
Kerr, B.J., Weber, T.E., Ziemer, C.J., Spence, C., Cotta, M.A., Whitehead, T.R. 2011. Effect of dietary inorganic sulfur level on growth performance, fecal composition, and measures of inflammation and sulfate-reducing bacteria in the intestine of growing pigs. Journal of Animal Science. 89:426-437.

Whitehead, T.R., Cotta, M.A., Falsen, E., Moore, E., Lawson, P.A. 2011. Peptostreptococcus russellii sp. nov., isolated from a swine-manure storage pit. International Journal of Systematic and Evolutionary Microbiology. 61(8):1875-1879.

Last Modified: 9/22/2014
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