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United States Department of Agriculture

Agricultural Research Service

Related Topics

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

Location: Bioenergy Research Unit

2012 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 FY12, research continued on studying the inhibitory effects of quebracho and other tannins on production of total gas, methane, and the odorous compound hydrogen sulfide from manure slurry under laboratory conditions, and the analyses of antibiotic resistance in manure. A variety of tannin preparations were fractionated into larger and smaller molecular sizes using chemical extraction to further delineate the active inhibitory components of the tannins. Initial experiments suggested that the lower size material from all tannin preps, not just quebracho, was inhibitory, and further analyses of these fractions will be carried out. Collaborative research was continued with Michigan State University on the combined effects of quebracho tannins and borax on inhibiting emissions from swine manure. This research applied molecular techniques to quantify the bacteria responsible for production of hydrogen sulfide and the effects of condensed tannins and borax on these bacterial populations. This work relates to Objective 1 of the project. Antibiotic genes present in swine feces and manure were identified by PCR techniques. This work relates to Objective 2 of the project. These results were communicated to the scientific community via presentations at domestic/international meetings and scientific publications.


4.Accomplishments
1. Antibiotic resistance genes were identified in swine feces and manure. Bacteria commonly present in swine feces and stored manure may provide reservoirs of antibiotic resistance genes which may possibly be transferred to bacteria affecting human health. However, relatively little is known about such genes in these ecosystems. Agricultural Research Service (ARS), Bioenergy Research Unit scientists at the National Center for Agricultural Utilization Research (NCAUR), Peoria, IL, demonstrated that a variety of antibiotic resistance genes are present in both swine feces and stored swine manure. These results will guide the development of methods to quantitatively measure each of these genes in these ecosystems and assess the impact of varying management practices on reducing the concentration of such genes. Such reductions will aid swine producers, environmental protection agencies, health officials, and local residents that live near swine facilities.


Review Publications
Poulsen, H.V., Jensen, B.B., Finster, K., Spence, C., Whitehead, T.R., Cotta, M.A., Canibe, N. 2012. Microbial production of volatile sulphur compounds in the large intestine of pigs fed two different diets. Journal of Applied Microbiology. 113:143-154.

Hamady, Z.Z., Scott, N., Farrar, M.D., Wadhwa, M., Dilger, P., Whitehead, T.R., Holland, K.T., Lodge, J.P., Carding, S.R. 2011. Treatment of colitis with a commensal gut bacterium engineered to secrete human TGF-beta1 under the control of dietary xylan. Inflammatory Bowel Diseases. 17(9):1925-1935.

Last Modified: 9/1/2014
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