Ana Barreiro: «The use of antibiotics in livestock farming may pose a risk of contamination»

Soil is essential for life. Ulysses, who knelt to kiss it when he returned to Ithaca, knew this better than anyone. Soil is where food grows, and homes are built. But human activities leave a profound mark on it. Ana Barreiro is dedicated to observing it very closely.

With a degree in Biology and a PhD cum laude in Environment and Natural Resources, the Campus Terra researcher focused her thesis on the impact of fire extinguishing agents and post-fire restoration practices on soil microbiota. 2017, she traveled to Sweden to continue her career at the Swedish University of Agricultural Sciences (SLU). After four years, she returned to her home university with a Juan de la Cierva contract.

Currently, Ana Barreiro is part of the Environmental and Sustainable Forestry Management Unit (UXAFORES), where she analyzes how human uses of soils affect microorganisms and examines the influence of antibiotics used in livestock and human medicine, which can reach soils through slurry and sewage sludge and from there can be incorporated into the trophic chain.

The doctor combines these lines of research with the participation in a group of experts of the European Commission and with teaching, as she teaches Geology and Climatology in the Degree in Agricultural and Agri-Food Engineering and the Degree in Forestry and Natural Environment Engineering of the Terra Campus.

Even so, Ana Barreiro finds time to cultivate her love for traditional Galician music, specifically for the tambourine, an instrument she used to play in a folk music group. And, to keep her feet on the ground, she attends traditional dance classes at an association in Lugo.

Talking to her undoubtedly helps us to understand the world we live in better.

-You are a microbial ecology specialist and responsible for the soil microbiology laboratory of the EPSE at Campus Terra. What is the basis of your work? What activities are you focused on?

-I am responsible for a soil microbiology laboratory at the Higher Polytechnic Engineering School. My work is focused on the analysis of how soil microorganisms, which are essential to have a healthy, productive soil with the capacity to fix atmospheric C, are affected by the management we do of them, both forestry and agricultural, from the point of view of microbial activity and community structure.

-One of the last research projects of the UXAFORES group to which you belong is focused on analyzing soil contamination derived from using antibiotics in livestock. What is the dimension of the problem? Does this research arise from any previous approach, or are you going to assess the reality of the problem?

-The use of antibiotics in livestock farming can pose a risk of contamination by these compounds in the environment because animals can excrete up to 85% through feces and urine, ending up in manures and slurries that are added to agricultural soils as fertilizers. There is a risk of transfer of antibiotics from the soil to the plant, but this will depend on the properties of the soil and those of the drug. In this sense, many soils have a high absorption capacity for some antibiotics, preventing their entry into the food chain. If not, they can affect environmental and even human health, but the most severe problem they cause is the generation of antibiotic-resistant bacteria.

Spain is among the countries in Europe where most antibiotics are given to farm animals, and Galicia is no exception. Given the scope of the problem, the European Union itself proposed a law in 2022 to regulate and limit the use of these drugs.

However, there is one exception: the ionophore antibiotics, which are used to fight coccidiosis. These compounds can continue to be used as animal feed additives, which are prohibited with other antibiotics and do not require a veterinary prescription.

The project we are working on seeks to detect the presence of antibiotics in soils fertilized with slurry and manure from medicated animals, focusing primarily on anticoccidials. Our objective is to assess Galicia's situation regarding these compounds. Still, we start from a previous group project where antibiotics for human use were detected in soils where sewage sludge was added.

-In case you detect significant soil alterations in certain areas with relevant livestock activity, how could the problem be combated? It does not seem easy to mitigate the use of antibiotics in the industry.

-One of the ways to combat the problem would be to favor the absorption of antibiotics by soils to avoid their passage to crops or water courses. In this project, we will also study how we can use different by-products of the forestry and food industries as biosorbents of these compounds. We are working with by-products such as mussel shells, wood ash and bark, or residues from olive oil production.

The use of antibiotics in the industry favors healthy and productive animals. It would be appropriate to mitigate their use by applying them more precisely, medicating only the sick animals, but that is not easy and true. The European-level regulations follow this path, so I hope that this will be a reality in the medium to long term.

-You joined the UXAFORES group in 2021 with a Juan de la Cierva grant. How do you assess this stage after three years of work?

-The assessment is very positive. In the professional field, I joined a very active group that does research on different topics, favors collaboration with researchers from other fields, and supports newer researchers, as is my case. On a more personal level, the work environment is unbeatable. Overall, I am delighted to be part of UXAFORES.

-UXAFORES is a 360 research group: soils, plant nutrition, forest planning, wood uses, pests, fires... Today, more than ever, what you do to take care of the planet and society as a whole is more critical and decisive than at any other time in history. Are you aware of that?

-I don't know to what extent we are aware or not of the importance of our research; it depends on the person. What I do is essential to understand better our soils, which are the basis of life. I also believe in disseminating this knowledge among the different social agents.

Climate change is here to stay, and studies like those in our group are fundamental to better understanding and caring for the environment in this adverse situation.

-Between 2017 and 2021, you worked at the Swedish University of Agricultural Sciences. How do you evaluate that stage of your life? What do you take away from your stay in Sweden?

-It was an excellent stage, of which I have enjoyable memories. I worked with people from many different countries who are still friends today. I learned new things, overcoming the challenges that were put in my way, which helped me grow as a researcher. During my stay, I kept the people I was lucky to meet and the notion that there is not only one way to work in science, and all of them are valid.

-At SLU, you worked on the international Bioinvent project, and your work was vital because you established the PLFA technique that determined the initiative's success. What was that contribution?

-I learned this technique: characterizing the microbial community of soils through their fatty acid profile while completing my doctoral thesis at the CISC's Galician Agrobiotrophic Research Institute. When I joined the Bioinvent project at SLU, this technique was part of the proposal, but it was not developed in the university laboratories, a task that I took over.

Once that work was done, we successfully analyzed the 348 samples from different meadows in the project and published the results in a scientific journal.

-You are also a member of a group of high-level European Commission experts who establish recommendations for designing and structuring legislative proposals related to organic farming. What is your role within this group, and where are your proposals heading?

-The appointment as a member of this group is relatively recent. My role is, along with other researchers from different countries in Europe, to make recommendations based on scientific knowledge and prepare reports with them that are made available to the various member states of the European Union. Right now, we are working on the regulation of fertilizers used in organic farming.