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ARS Home » Research » Publications at this Location » Publication #198458
Title: SURVIVAL OF ESCHERICHIA COLI IN COW PATS IN PASTURE AND IN LABORATORY CONDITIONS

Author
item Van Kessel, Jo Ann
item Pachepsky, Yakov
item Shelton, Daniel
item Karns, Jeffrey

Submitted to: Journal of Applied Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/27/2007
Publication Date: 10/1/2007
Citation: Van Kessel, J.S., Pachepsky, Y.A., Shelton, D.R., Karns, J.S. 2007. Survival of Escherichia coli in cow pats in pasture and in laboratory conditions. Journal of Applied Microbiology. 103(4):1122-1127.

Interpretive Summary: A thorough understanding of environmental factors responsible for the survival of fecal-borne bacteria is critical for evaluating management practices aimed at decreasing bacterial contamination of water from land-applied manures or fecal deposition. Escherichia coli is the indicator organism used to identify impaired streams and water bodies. Relatively little is known about the inactivation rates of FC or E. coli in animal feces deposited on pasturelands, or the relative importance of the different environmental factors. Comparisons of field and laboratory survival data have produced contradictory results. The overall objective of this work was to investigate the survival of E. coli in bovine fecal cow pats deposited on pasture vs. those incubated in a controlled laboratory environment at comparable temperature regimes. Environmental variables evaluated were source of feces (animals with different diets), placement of cow pats on pasture (exposed vs shaded) and moisture content. Fecal samples were collected from three cow herds on different diets. Samples were deposited as shaded and non-shaded cow pats in a field and incubated in the laboratory. Fecal coliforms and Escherichia coli were enumerated in subsamples taken during a month. In both field and laboratory conditions, fecal coliform concentrations substantially increased during the first week and subsequently decreased. In field incubations, the rate of decline was affected by fecal source with the decline being faster in dairy vs. beef herd cow pats. Under laboratory conditions, time, water content, source, and temperature all significantly affected changes in FC concentration. E. coli proportion was not significantly affected by the source or time in field incubations but both time and temperature were significant factors in laboratory incubations. Inactivation rates were larger in the field than in the laboratory.Overall comparison of laboratory and field data shows that the factors affecting inactivation manifested themselves similarly in both environments, although inactivation rates were different.

Technical Abstract: Aims: To compare survival of E. coli in bovine feces deposited in a pasture or incubated in a controlled laboratory environment at comparable temperature regimes. Methods and Results: Fecal samples were collected from three cow herds on different diets. Samples were deposited as shaded and non-shaded cow pats in a field and incubated in vitro. Fecal coliforms and Escherichia coli were enumerated in subsamples taken during a month. In both field and laboratory conditions, fecal coliform concentrations substantially increased during the first week and subsequently decreased. In field incubations, the rate of decline was affected by fecal source with the decline being faster in dairy vs. beef herd cow pats. Under laboratory conditions, time, water content, source, and temperature all significantly affected changes in FC concentration. E. coli proportion was not significantly affected by the source or time in field incubations but both time and temperature were significant factors in laboratory incubations. Inactivation rates were larger in the field than in the laboratory. Conclusions: Factors affecting the fecal coliform inactivation manifested themselves similarly in both environments. However, inactivation rates were different. Significance and Impact of the Study: This study underscores the importance of field data on inactivation of manure-borne fecal coliform and indicates the need in and the type of corrections that have to be applied to the results of laboratory manure-borne coliform inactivation experiments.