HELSINKI, Finland – A new study has revealed that microplastics – tiny plastic particles pervasive in agricultural environments – interact with and disrupt the microbial ecosystem in the rumen, the first stomach chamber of cattle, according to researchers.

“Our work is a first step toward understanding the biological consequences of microplastic exposure in farm animals,” said Daniel Brugger, University of Helsinki associate professor of production animal nutrition and lead researcher. The microbial ecosystem is bacteria, fungi and viruses, interacting with each other and their non-living environment.

Brugger added that there is an urgent need for in-vivo studies, which are experiments conducted on a whole, living organism, including animal models and humans, to better understand the impacts on animal health and food safety, especially as global plastic production continues to rise.

Published in the Journal of Hazardous Materials, the findings come from a joint study by the University of Helsinki, the University of Zurich, the University of Hohenheim, and Technical University of Munich, showing how microplastics are transformed within the digestive system of farm animals and the potential risks for animal health, productivity and food safety, the researchers said.

According to the study, using a controlled laboratory fermentation system, researchers incubated rumen fluid from cows with hay or barley and five common types of microplastics found in agricultural settings: polylactic acid (PLA); polyhydroxybutyrate (PHB); high-density polyethylene (HDPE), polyvinyl chloride (PVC), and polypropylene (PP).

A controlled laboratory fermentation system is an apparatus designed to provide a precisely monitored and regulated environment for the cultivation of microorganisms, such as bacteria, yeast or fungi, to produce specific products. The microplastics were tested in various particle sizes and doses to evaluate their impact on rumen fermentation, microbial activity, and the plastics themselves.

Researchers said all tested microplastics did not remain inert (lack the ability or strength to move) in the rumen; instead, they interacted with the microbial ecosystem, altering fermentation and microbial functions. Researchers added that the presence of microplastics consistently reduced cumulative gas production, a key indicator of overall fermentation activity, regardless of plastic type, particle size or dose.

While previous research has established that livestock are exposed to microplastics through contaminated soils and feed, the researchers said it was unclear whether these particles remained unchanged or interacted with microbiome (i.e., bacteria, fungi and viruses).

“Our study shows for the first time that microplastics do not simply pass through the digestive tract of farm animals,” said Jana Seifert, University of Hohenheim professor of functional microbiology of livestock in Hohenheim, Germany.

“Instead, they interact with the gut microbiome to alter fermentation processes, and are partially broken down,” she said. “This means farm animals are not passive recipients of plastic pollution; their digestive systems may act as bioreactors that transform microplastics and redistribute them within agricultural systems.” A bioreactor is a system that provides a controlled environment for biological organisms like cells, microbes or tissues to grow and perform biochemical reactions.

Grant Dewell, Iowa State University associate professor of veterinary medicine and beef extension veterinarian, told Farm World, “We have seen, the over the last few years, the potential that microplastics may have. This study is an interesting first look at what some of those potentials in cattle could be.

“This was an in-vitro experiment, meaning that the experiment was done in a lab with a simulated ruminal environment,” he said. “They found that adding microplastics to the simulated rumen changed the bacteria that were there, and the fermentation process to some degree.”

He said it was also interesting that microplastic size was also reduced, indicating that the fermentation process was also affecting the plastic: “It is hard to extrapolate specifically what this means to an individual animal in that a real rumen is a more dynamic environment, so we won’t know for sure the impact until the study is actually conducted in live animals.

“Since microplastics are such a concern, and if we are reducing particle size in the rumen, then there is more potential for absorption of microplastics, which has some direct impacts on health and reproduction that we know of, plus it could lead to the accumulation of microplastics in the food chain,” he added.

Researchers raised the need for better management of plastic use in agriculture, including silage films, packaging materials, and sewage sludge on fields, to reduce microplastic contamination in animal feed.

“Plastic pollution isn’t just an environmental issue ‘out there,’” said Cordt Zollfrank, Technical University of Munich professor of biogenic polymers, which are produced by the cells of living organisms. “It has direct biological consequences for farm animals, and potentially for humans, through the food chain.”

Dewell said the main management of microplastics is removing loose plastic from the environment: “Probably the biggest culprit we see is the net wrap on round bales. In some cases, we have seen intestinal blockage from cattle eating a large mass of bale wrap, but as this research indicates, smaller pieces may be more insidious.”

He said farmers should remove the bale wrap before, especially when grinding since that process increases the number of small particles; and feeding or bedding since cattle will chew on the bale wrap from cornstalk bales.

“Other large pieces of plastic, such as silage covers and packaging material, should be kept out of not only the feed but the environment in general as cattle will chew on things they shouldn’t,” he said. “The contamination that we already see with microplastics in the environment will be impossible to eliminate now, and the source is beyond our general control.

“For now, focus on the bigger issues until we know more about what impact microplastics have, and what some potential mitigation strategies may be,” he added.