Degree Type
Thesis
Date of Award
2019
Degree Name
Master of Science
Department
Agricultural and Biosystems Engineering
Major
Agricultural and Biosystems Engineering
First Advisor
Michelle L. Soupir
Second Advisor
Adina Howe
Abstract
Agriculture is an economic cornerstone in Iowa and the surrounding states, as well as arguably the entire United States as a whole. However, there is growing concern about the use of antibiotics in the animal agriculture sector and its contribution to antibiotic resistance (Levy & Marshall, 2004). Yet it is still unclear how antibiotic resistance is affected by the environment at the field scale and what mechanisms can be employed to minimize the transport. This three-year study monitors both phenotypic and genotypic antibiotic resistance markers in subsurface drainage from research plots with varying manure application times and tillage practices. Enterococcus and tylosin and tetracycline-resistant Enterococcus were monitored as well as three antibiotic resistant genes (ermB, ermF, tetM) to 1) quantify antibiotic resistant bacteria (ARB) and antibiotic resistant genes (ARGs) in subsurface drainage 2) evaluate the impact of field management practices, manure application timing and tillage both the antibiotic resistant bacteria (ARB) and antibiotic resistant genes (ARGs), and 3) assess relationships between phenotypic and genotypic indicators of antibiotic resistance. Results of the study show overall low levels of both ARB and ARGs leading to further research questions with the targeted improvement of new methods. Although recommendations on specific field management practices best suited to minimize ARB and ARG transport cannot be drawn from the results of this study, it was shown that manure application in the spring had the strongest potential for future research.
Copyright Owner
Hannah Elizabeth Guyer
Copyright Date
2019-08
Language
en
File Format
application/pdf
File Size
74 pages
Recommended Citation
Guyer, Hannah Elizabeth, "Impacts of manure application timing and tillage practices on antibiotic resistant bacteria and genes in drainage water from manured fields" (2019). Graduate Theses and Dissertations. 17458.
https://lib.dr.iastate.edu/etd/17458