ARS | Publication request: Spatial variation of nutrients, pharmaceuticals and bacteria across a cattle backgrounding operation

Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 20, 2012
Publication Date: N/A

Interpretive Summary: Beef cattle backgrounding operations that grow out weaned calves for feedlot finishing can become sources of environmental contaminants. Better understanding of these contaminants and their distribution will aid in development of effective contaminant management guidelines for sustainable livestock production. This research investigated soil nutrients, bacteria, and veterinary pharmaceutical concentrations across a small cattle backgrounding feedlot on a karst landscape. Results indicated that all contaminants were highly concentrated in the feeder area (FD) and were lower in the other feedlot areas. FD soils had 8.2 pH, 5.9% organic matter (SOM), 2002 mg kg-1soil test phosphorus (STP), 99.7 mg kg-1ammonium N (NH4-N), and 18.3 mg kg-1nitrate N (NO3-N). The other sites were slightly acidic and contained 3.9% SOM, 273 mg kg-1STP, 21.5 mg kg-1NH4-N, and 2.0NO3-N mg kg-1. Bacterial populations in the FD area averaged 2.7x1010 total cells, 3.9 x108 Bacteriodes sp., 2.9x 108 Enterococcus sp., and 4.5x 105 E. coli cells g-1soil. Concentrations of Bacteriodes sp.and Enterococcus sp. were 1 to 4 orders of magnitude lower at the other sites. E coli showed lower dynamic range and were generally uniformly distributed across the landscape. Antibiotic and parasiticide concentrations in the FD area were 86.9 ng g-1monensin, 25.0 ng g-1 lasalocid and 10.3 ng g-1doramectin. These compounds were 6 to 27 fold lower in the other feedlot areas. Grazing pastures within small feedlots can offer effective hydrologic isolation from contaminants. Therefore, contaminant management plans for small feedlots should focus on feeder areas where nutrients, bacteria and pharmaceutical compounds are most concentrated.

Technical Abstract: Beef cattle backgrounding feedlot systems that grow out weaned calves for feedlot finishing can become potential diffuse sources of environmentally significant contaminants. Better understanding of these contaminants and their distribution will aid in development of effective contaminant management guidelines for sustainable livestock production. This research investigated soil nutrients, bacterial communities, and residual veterinary pharmaceutical concentrations across a small beef cattle backgrounding feedlot operation located on a karst landscape?. Results indicated that all contaminants were highly concentrated in the feeder area (FD) and in the nearby grazing area (GR). Concentrations were lower in the retention basin (RB) and sinkhole areas (S). Feeder area soils had 8.2 pH, 5.9% organic matter (SOM), 2002 mg kg-1soil test phosphorus (STP), 99.7 mg kg-1ammonium N (NH4-N), and 18.3 mg kg-1nitrate N (NO3-N). The other site locations were slightly acidic and contained 3.9% SOM, 273 mg kg-1STP, 21.5 mg kg-1NH4-N, and 2.0 NO3-N mg kg-1. Bacterial populations in the FD area averaged 2.7x1010 total cells, 3.9 x108 Bacteriodes sp., 2.9x 108 Enterococcus sp., and 4.5x 105 E. coli cells g-1soil. Concentrations of Bacteriodes sp.and Enterococcus sp. were 1 to 4 orders of magnitude lower at the other site locations. Concentrations of E coli showed lower dynamic range and were generally uniformly distributed across the landscape.Concentrations of anitibiotics were 86.9 ng g-1monensin, 25.0 ng g-1 lasalocid and 10.3 ng g-1doramectin in the FD area. These compounds were 6 to 27 fold lower in the other feedlot areas. Grazing pastures within small feedlots can offer effective hydrologic isolation for highly contaminated areas.