Animal Feed Components and the Impacts of Land-applying Manure on Soil Bacterial Biodiversity and Antibiotic Resistance
Amy R. Sapkota, PhD, MPH Powerpoint Slides
Animal feeding practices in the U.S. have changed considerably over the past century. As large-scale, concentrated production methods have become the predominant model for animal husbandry, animal feeds have been modified to include ingredients ranging from rendered animals and animal waste to antibiotics and organoarsenicals. In the first part of this presentation, I will discuss results from a review article that we compiled regarding current animal feeding practices in the U.S., etiologic agents present in feed and the resulting potential human health effects. Our major findings from this work emphasize that current animal feeding practices can result in the presence of bacteria, antibiotic-resistant bacteria, prions, arsenicals, and dioxins in feed- and animal-based food products. Despite a range of potential human health impacts that could ensue, there are significant data gaps that prevent comprehensive assessments of human health risks associated with animal feed.
In the second part of this presentation, I will discuss some of the environmental impacts associated with one particular animal feed practice: the use of non-therapeutic levels of antibiotics for growth promotion. Specifically, I will discuss the findings from a study that we conducted to explore antibiotic resistance and bacterial biodiversity in French agricultural soils that were amended with antibiotic-containing pig manure. Our major findings from this study indicate that there are some differences in levels of antibiotic resistance and bacterial biodiversity in soils amended with pig manure versus control soils that were not impacted by manure.
The overall implications of both of these studies are that some current animal feeding practices, as well as the land application of animal manure—the quality of which is heavily influenced by specific feed ingredients—have the potential to adversely impact both human and environmental health. It is possible that these adverse impacts could be attenuated through changes in animal feeding practices, including shifts to antibiotic-free and/or organic feeds, which are currently feasible in animal production facilities in both the U.S and Europe.
Amy R. Sapkota received a PhD in Environmental Health Sciences from the Johns Hopkins Bloomberg School of Public Health, an MPH in Environmental Health Sciences from the Yale School of Public Health and a BS in Biology from the University of Maryland, College Park. She completed postdoctoral fellowships at the Johns Hopkins Bloomberg School of Public Health and the Environmental Microbial Genomics Group within Le Centre National de la Recherche Scientifique in Lyon, France. Dr. Sapkota's research interests lie in the areas of microbial environmental exposure assessment and environmental epidemiology, with a focus on evaluating the complex relationships between the environment, food and water production systems, and human infectious diseases. Current research projects include: 1) evaluating the dissemination of antibiotic-resistant bacteria and resistance genes from agricultural sources into air, surface water, groundwater, soil and food products, and understanding how this may contribute to rises in antibiotic-resistant bacterial infections in humans; and 2) utilizing metagenomic methods to understand total bacterial and viral biodiversity in environmental samples including soil, food, air and other commercial products. Other interests include the environmental and human health impacts associated with the discharge of wastewater treatment effluent into the Chesapeake Bay and the use of tertiary-treated municipal wastewater for spray irrigation.
