Cattle (Bos taurus) grazing on unimproved pastures can be a significant, yet often overlooked, source of pollutants to surface waters, especially when the cattle have unlimited access to streams in the pastures. Livestock exclusion from streams has been demonstrated to reduce sediment and possibly nutrient yield from streams draining pastures. The purpose of this study was to evaluate the effects of excluding dairy cows from, and planting trees in, a 335-m-long and 10-to 16-m-wide riparian corridor along a small North Carolina stream. Analysis of 81 wk of pre-exclusion and 137 wk of post-exclusion fencing data documented 33, 78, 76, and 82% reductions in weekly nitrate + nitrite, total Kjeldahl nitrogen (TKN), total phosphorus (TP), and sediment loads, respectively, from the 14.9-ha pasture area adjacent to the fenced section of stream. Statistical analyses by t-tests and analysis of variance suggested that the reductions in mean weekly loads post-fencing were significant (P < 0.05) for all pollutants except nitrate + nitrite. Thus, the results indicated that livestock exclusion and subsequent riparian vegetation establishment was effective at reducing pollutant export from an intensively grazed pasture.

Salmonella enterica is an important foodborne pathogen, and contamination of surface and ground water that may result from various human activities, such as animal production and urbanization, may contribute to the public health burden. The aims of this study was to determine the sources of Salmonella contamination in four different types of watersheds and to assess the relative contribution of multidrug-resistant strains. Eighty-six water samples collected from four different watershed systems, including those impacted by swine production (n = 12), residential/industrial (n = 34), crop agriculture (n = 12), and forestry (n = 28), were cultured for Salmonella and further characterized by serotyping, antimicrobial susceptibility testing, and pulsed-field gel electrophoresis genotyping. Salmonella prevalence was high in all four watersheds: residential/industrial area (58.8%), forestry (57.1%), crop agriculture (50%), and swine production (41.7%). Majority of the Salmonella isolates (87.1%) were pansusceptible. Multidrug resistance up to eight antimicrobials (R-type: AmStTeAxChCeKmGm) was detected in water samples that originated from swine production systems only. Serovars identified included Anatum, Gaminara, and Inverness (18.3% each) and Muenchen and Newport (8.7% each), Bredeny (7.6%), and Montevideo (6.8%). Pulsed-field gel electrophoresis analysis indicated genotypic relatedness among Salmonella recovered from residential/industrial and forestry-associated watersheds (genotypic cluster types A, C, D, E, F, G, H, and J), sites with relatively close geographic proximity. Swine-production-associated isolates were distinctly different from the others (genotypic cluster types B and I), corroborating the phenotypic findings. Overall, the findings suggest that all the various watersheds, including natural forest, remain important contributors of Salmonella contamination. While swine-production-associated water samples were not found to have a disproportionately high prevalence, it was the most important reservoir of multidrug-resistant strains.

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Because of the relatively high variability of pollutant export from urban land uses, a significant number of monitoring studies, including data from many storms, are needed to adequately characterize export from urban land uses. Pollutant runoff from six small drainage areas with different land uses was monitored for at least 20 storm events over the course of more than 1 year. The land uses included singlefamily residential, golf course, industrial, dairy cow pasture, construction site, and wooded site. Average event mean concentrations and total annual load were computed for nitrogen forms, total phosphorus, and sediment from the land uses. Annual total nitrogen export was greatest for the construction land use during the house-building phase, followed closely by the residential and golf course land uses. Total phosphorus export was greatest for the golf course site followed by the pasture and residential land uses. Sediment export was greatest for the construction site during the rough grading phase, which averaged more than 10 times more sediment export than any of the other sites. To estimate export from a multiuse urban watershed, total nitrogen, phosphorus, and sediment export from the residential, golf course, and construction sites were averaged. The average total nitrogen, phosphorus, and sediment export from the three land uses was, respectively, 269, 302, and 256% greater than the corresponding exports from the wooded site, which was considered similar to the predevelopment land use. Additionally, analyses of rainfall samples indicated that a considerable portion of the nitrogen export from these sites likely comes from nitrogen in rainfall. Water Environ. Res., 74, 100 (2002).