Survival of Escherichia coli in Beef Cattle Fecal Pats Under Different Levels of Solar Exposure

Abstract

Understanding the survival and transport of Escherichia coli in feces on land and in water is important when trying to assess contamination of water by grazing animals. A fecal-pat experiment was conducted in July and August of 2003 to investigate the survival of E. coli under 4 levels of solar exposure controlled by using shade cloth. Fresh beef cattle manure was uniformly blended to produce 2.5-and 1.6-kg fecal pats, which were placed in plastic trays or in contact with the soil and covered with 0%, 40%, 80%, or 100% shade cloth treatments and replicated 5 times. Samples from each fecal pat were collected at Time 0 to establish E. coli levels; sampling was repeated at Day 1, Day 3, and approximately weekly thereafter for 45 days to determine die-off. E. coli concentration and percent moisture were measured for each fecal sample. At the end of the experiment, fecal pats under the 0% shade cloth had the lowest E. coli concentrations, followed by the 40%, 80%, and 100% treatments, with 0.018, 0.040, 0.11, and 0.44 3 10 6 colony-forming units (CFU) g À1 , respectively. Fecal-pat size was significant only on Day 17, when large fecal pats had higher concentrations of E. coli (P , .0001). There was no significant difference (P ¼ 0.43) in E. coli concentration between the fecal pats in contact with the soil vs. those in plastic trays. Percent moisture of fecal pats was not a good covariate. Age of fecal pats, as well as exposure to solar radiation negatively influences the survival of E. coli. From a management perspective, E. coli in fecal pats under forested situations would survive longer than in open grasslands due to shading, and any possible contamination by E. coli would be greatest within 7 days of removing cattle from a riparian area or pasture. Resumen Entender la supervivencia y transporte de E. coli en las heces sobre el tierra y en el agua es importante cuando intentamos evaluar la contaminació n del agua por los animales en apacentamiento. En Julio y Agosto del 2003 se condujo un experimento con tortas de heces fecales para investigar la supervivencia del E. coli bajo cuatro niveles de exposició n solar controlada usando una tela para sombreado. Estiércol fresco de ganado bovino para carne fue mezclado uniformemente para producir tortas de 2.5 y 1.6 kg, que se colocaron en charolas o en contacto con el suelo bajo tratamientos de 0%, 40%, 80%, y 100% de sombreado repetidos cinco veces. Muestras de cada torta fecal se colectaron en el tiempo cero para establecer los niveles de E. coli y en el día uno, día tres y aproximadamente cada semana durante 45 días para determinar la diná mica de mortalidad de la bacteria. La concentració n de E. coli y humedad se midieron en cada muestreo fecal. Al final del experimento, las tortas fecales bajo 0% de sombreado tuvieron las menores concentraciones de E. coli, seguida por los tratamientos de 40%, 80%, y 100% (0.018, 0.040, 0.11, y 0.44 3 10 6 unidades formadoras de colonias (CFU) g À1 respectivamente). El tamañ o de la torta fecal fue significativo solo en el día 17, ...

Decay of Fecal Indicator Bacterial Populations and Bovine-Associated Source-Tracking Markers in Freshly Deposited Cow Pats

“…After initial regrowth, E. coli populations decayed faster than enterococci in unshaded cow pats. Similar results were reported by Meays et al (37), who indicated that shading was the only significant factor enhancing survival of E. coli from day 17 to day 45. In contrast, Van Kessel et al (36) reported minimal differences in die-off rates between shaded and unshaded treatments; however, their shaded cow pats were placed under a tree, which would not have shielded them completely from sun or rain, resulting in a statistically insignificant die-off difference between both treatments.…”

“…Regrowth of E. coli for up to 7 days has been well documented in the literature (14,(34)(35)(36). Meays et al (37) observed E. coli increases on days 1 and 7 under 40% and 0% shading, respectively, which suggests that E. coli can replicate in the environment. Sinton et al (12) reported that growth was determined primarily by manure water content and secondarily by temperature, while Muirhead and Littlejohn (34) concluded that temperature was the responsible factor.…”

“…In contrast, Van Kessel et al (36) reported minimal differences in die-off rates between shaded and unshaded treatments; however, their shaded cow pats were placed under a tree, which would not have shielded them completely from sun or rain, resulting in a statistically insignificant die-off difference between both treatments. The most significant effect of shading, which is considered important to enhancing survival of FIB in cow pats, can be attributed to protection from UV (12,15,37). Furthermore, UV-B has been reported to have a more lethal effect on bacterial DNA inactivation than that of UV-A (15,16,(40)(41)(42)(43)(44)(45).…”

“…Some reports indicate that MC has a positive correlation with FIB concentration (12,(24)(25)(26)(27); however, Wang et al (14) reported a higher overall reduction in E. coli levels at 83% MC at 27°C, but no effect at 55% and 30% MC. Meays et al (37) showed that the MC of fecal pats at sampling time was not correlated with the concentration of E. coli.…”

Soil and faecal material reservoirs ofEscherichia coliin a grazed pasture

“…The majority of studies on the survival of faecal microorganisms in agriculture have focused on the application of manures spread to land rather than direct deposition by grazing animals (Hutchison et al 2005;Oliver et al 2007). Studies on the survival of faecal bacteria in, and losses of faecal bacteria from, cowpats have generally been conducted using artificially created cowpats of a consistent size (Thelm& Gifford 1983; Kress & Gifford 1984;Schijven et al 2004;Meays et al 2005;Muirhead et al 2005;Sinton et al 2007), and yet visual observation of a grazed pasture indicates that the size of cowpats is not uniform. Furthermore, survival studies have focused on the die-off of the microorganisms and ignored the physical decomposition of the faecal material (Crane & Moore 1986).…”