In this webinar, representatives from multiple sectors of the livestock production industry are featured to learn how each sector is approaching the complex problem of antibiotic resistance with management strategies to improve antimicrobial stewardship in live animal production and across the food production system. This presentation was originally broadcast on August 20, 2021. Continue reading “Addressing Antimicrobial Resistance Through Livestock Management”
A brief summary of the manuscript, Summary of veterinary antibiotics in the aquatic and terrestrial environment (Kemper, 2008), a review of studies looking at the presence of clinical antibiotics in the native environment.
- All antibiotics used by people or animals contribute to the development of antimicrobial resistance (AMR).
- Antibiotics used in livestock production have the potential to contribute to increasing pools of antibiotics in soil due to manure application or deposition.
- The biggest contributor to antibiotics in the surface water is a likely municipal (human) waste.
The purpose of this research was to investigate the degradation of four animal husbandry antibiotics during anaerobic digestion (AD) and study biogas inhibition from the antibiotics. This study was designed to fill information gaps related to AD inhibition by different antibiotic classes in diluted manures received by anaerobic digesters, particularly cattle manure, and the need to more thoroughly investigate antibiotic degradation products from the AD process.
What did we do?
We conducted AD bench-scale experiments that investigated biogas inhibition and antibiotic degradation. First, cattle manure was added to glass bottles. A known amount of antibiotic standard was added to the manure. A small amount of dilution water was added and the manure-antibiotic slurry was mixed briefly. Then, anaerobic digestion inoculum was added to the bottle. The air in the bottle was purged with nitrogen gas. Finally, the bottles were sealed and placed in an incubator set at 37°C. Biogas measurements and small liquid samples for antibiotic analysis were taken daily. At the end of the 40 day AD study, the solids were extracted to determine the amount of antibiotic adsorbed to the solids.
What have we learned?
Results from our research showed that three out of four antibiotics degraded within 5 days of AD. Several degradation products were detected, some of which could be biologically active. The antibiotic that did not degrade was mostly found in the liquid phase of the AD reactor slurry and a small portion was adsorbed to the solids. Our results suggest that when antibiotic contaminated feedstocks are added to AD reactors, persistent antibiotics and transformation products may contaminate the liquid and solid effluents.
Our results showed the one of the antibiotics tested was more toxic to the AD process. Approximately 6.4-36 mg/L florfenicol lowered biogas production by 5-40%. Greater than 91 mg/L of the other antibiotics was needed to lower biogas production. These higher concentrations can be found in urine and feces of treated animals but they are not typical for the AD reactor following the addition of multiple feedstocks, inoculum, and dilution water. Our results suggest that there is little concern for these antibiotics to lower biogas production when cattle manure is used as an AD feedstock because the antibiotic concentration should be below inhibitory concentrations.
Future research plans are to investigate the microbial population change in anaerobic digesters due to antibiotic contaminated cattle manure.
Shannon Mitchell, Post-doctoral Research Associate at Washington State University firstname.lastname@example.org
Craig Frear, Assistant Professor at Washington State University
This research was supported by Biomass Research Funds from the WSU Agricultural Research Center; and by the BioAg (Biologically Intensive Agriculture and Organic Farming) Grant Program of the Washington State University Center for Sustaining Agriculture and Natural Resources.
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