Environmental Fate of Zoonotic Bacterial and Protozoan Pathogens in a Beef Cattle Feedlot Runoff Control-Vegetative Treatment System.
Elaine D. Berry1, Bryan L. Woodbury1, John A. Nienaber1, Roger A. Eigenberg1, and Jeanette A. Thurston-Enriquez2. (1) USDA, ARS, U.S. Meat Animal Research Center, P.O. Box 166, Clay Center, NE 68933-0166, (2) USDA, ARS, University of Nebraska, 120 Keim Hall, East Campus, Lincoln, NE 68583
Understanding the survival of zoonotic pathogens in livestock manure and runoff is critical for protecting public health, determining environmental risks associated with these wastes, and for validating the effectiveness of manure and runoff treatment systems. Our objectives were to determine the incidence and fate of selected zoonotic bacterial and protozoan pathogens in an alternative beef feedlot runoff control-vegetative treatment system. Runoff from feedlot pen surfaces drains to a shallow 300-m long basin which provides temporary liquid storage and accumulates solids. When an adequate volume is attained, the liquid fraction is discharged from the basin into a 6 ha vegetative treatment area (VTA) of bromegrass. Samples collected every 2-3 weeks from August 2003 - October 2005 included manure from the pens, liquid and solids from the basin, and soil and hay from the VTA. The incidence of E. coli O157 and Campylobacter spp. was determined using standard cultural isolation procedures. A modification of EPA method 1623 was used for determining Cryptosporidium oocyst and Giardia cyst concentrations. Basin discharge introduced the pathogens and generic E. coli into the VTA. Without additional discharge, incidence of E. coli O157 and Campylobacter spp. in VTA soils decreased over time. Similarly, levels of generic E. coli initially decreased rapidly, but residual populations could persist for long periods. Cryptosporidium oocysts and Giardia cysts were infrequently recovered in VTA samples, indicating differences in sedimentation and transport as compared to the bacteria. Isolation of generic E. coli from fresh-cut hay from regions of the VTA that received basin discharge (12/30 vs. 1/30 control samples) indicates some contamination risk; however, no pathogens were recovered from hay following baling. This investigation indicates the runoff control system is effective for reducing environmental risk by removing pathogens from the feedlot runoff.