Capturing veterinary antibiotics found in agricultural field runoff
January 30, 2013
Veterinary antibiotics are important tools for treating disease in livestock animals. But the antibiotics can present challenges when they find their way onto agricultural fields and into surface waters. A team of researchers is working to intercept wayward antibiotics before they end up in lakes and streams, and they’re using a common agricultural management practice to do so.
Antibiotics are given to livestock to treat disease and enhance growth, but animals also excrete antibiotics in manure, which can then be spread on agricultural fields. From the fields, they can leach into groundwater or enter nearby surface waters. Antibiotics in these environments could potentially lead to poor water quality and resistant bacteria including pathogens.
A research team – with members from Westminster College, the University of Missouri, the University of Arizona, and the USDA-Agricultural Research Service – is intercepting the transport of antibiotics through the use of vegetative filter strips (VFS). VFS are areas of land with abundant plants created between fields and bodies of water to block runoff. In a study published in the Jan.-Feb. issue of Soil Science Society of America Journal, the research team, led by Irene Unger and Keith Goyne, evaluated the effect of antibiotics on the beneficial microbial communities found in VFS soil. They found that relatively large doses of antibiotics left the microbes largely unchanged, suggesting that VFS could be a suitable tool for capturing antibiotics in agricultural field runoff.
VFS are a widely-used management technique, and they provide many benefits including the reduction of surface water runoff, sediment transport, nutrient loss, and herbicide export. As researchers were studying these uses for VFS, Goyne had the idea to see if the strips could reduce antibiotic loss from fields as well. It turned out, they could.
“VFS can intercept surface runoff water, and the presence of perennial vegetation [in the strips] can lead to changes in soil properties that help capture and retain the antibiotics,” explains Goyne. “Also, with greater plant diversity, the microbial communities are expected to be more active and diverse, which should lead to greater degradation of trapped antibiotics.”
Many of the benefits of VFS, then, are due to the microbial community found within the soil. Because the microbes are so important, Goyne and his team next wanted to find out if the antibiotics being trapped by the VFS were changing or harming soil microbes. They treated soils from VFS with two common veterinary antibiotics and looked for changes in the function and composition of the microbial community as well as the development of antibiotic resistance.
No changes were seen in the composition of the microbial community in VFS soil after antibiotic treatment. While a small decrease in soil microbial activity was seen early after treatment, the effect was short-lived, and the activity rebounded quickly. Also, the researchers found no evidence for increased antibiotic resistance. Overall, the antibiotic treatment had little influence on soil microbes and the benefits of the VFS.
“This work suggests there is no immediate effect of relatively large antibiotic doses on microbial communities in VFS,” explain the authors. “The microbes should retain their beneficial functions.”
The researchers are encouraged by the outcome of this study, and they plan to study the interaction of VFS and antibiotics further. Says Goyne, “We next need to investigate long-term, low dosing of VFS soils. Those conditions might better represent conditions found in the field.” From these studies, the researchers hope to establish VFS as a useful management practice for capturing antibiotics in runoff.
This research was funded by The Center for Agroforestry at the University of Missouri through a cooperative agreement with the USDA-Agricultural Research Service.
View the abstract at https://www.soils.org/publications/sssaj/abstracts/77/1/100