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Appears in Collections:Biological and Environmental Sciences Journal Articles
Peer Review Status: Refereed
Title: Re-shaping models of E.coli population dynamics in livestock faeces: Increased bacterial risk to humans?
Author(s): Oliver, David
Page, Trevor
Heathwaite, A Louise
Haygarth, Philip M
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Keywords: die-off
E. coli
cattle faeces
Issue Date: Jan-2010
Citation: Oliver D, Page T, Heathwaite AL & Haygarth PM (2010) Re-shaping models of E.coli population dynamics in livestock faeces: Increased bacterial risk to humans?, Environment International, 36 (1), pp. 1-7.
Abstract: Dung-pats excreted directly on pasture from grazing animals can contribute a significant burden of faecal microbes to agricultural land. The aim of this study was to use a combined field and modelling approach to determine the importance of Escherichia coli growth in dung-pats when predicting faecal bacteria accumulation on grazed grassland. To do this an empirical model was developed to predict the dynamics of an E. coli reservoir within 1 ha plots each grazed by four beef steers for six months. Published first-order die-off coefficients were used within the model to describe the expected decline of E. coli in dung-pats. Modelled estimates using first-order kinetics led to an underestimation of the observed E. coli land reservoir, when using site-specific die-off coefficients. A simultaneous experiment determined the die-off profiles of E. coli within fresh faeces of beef cattle under field relevant conditions and suggested that faecal bacteria may experience growth and re-growth in the period post defecation when exposed to a complex interaction of environmental drivers such as variable temperature, UV radiation and moisture levels. This growth phase in dung-pats is not accounted for in models based on first-order die-off coefficients. When the model was amended to incorporate the growth of E. coli, equivalent to that observed in the field study, the prediction of the E. coli reservoir was improved with respect to the observed data and produced a previously unquantified step-change improvement in model predictions of the accumulation of these faecal bacteria on grasslands. Results from this study suggest that the use of first-order kinetic equations for determining land-based reservoirs of faecal bacteria should be approached with caution and greater emphasis placed on accounting for actual survival patterns observed under field relevant conditions.
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Rights: Published in Environment International by Elsevier. Environment International, Volume 36, Issue 1, January 2010, pp. 1 - 7.; This is the peer reviewed version of this article.; NOTICE: this is the author’s version of a work that was accepted for publication in Environment International. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Environment International, VOL 36, ISSUE 1, (January 2010). DOI 10.1016/j.envint.2009.08.006

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