06.08.2021: A recently published study in the journal Toxins involving researchers from the University of Veterinary Medicine Vienna investigated the extent to which pastures, important feed sources for dairy production, are contaminated by mycotoxins. The findings show that mycotoxins, secondary metabolic products from various mould species, represent an underestimated risk for grazing and forage-fed livestock as well as for humans. Another important finding is that the fungal contamination increases with increasing temperatures.

Pastures, key feed sources for grazing animals such as cows, sheep, goats and horses, can be contaminated with several secondary metabolites from fungi and plants with toxic or endocrine-disrupting activities that represent a risk for the health, reproduction and performance of these animals. The aim of the exploratory study by Vetmeduni Vienna was to determine the co-occurrences and concentrations of a wide range of mycotoxins, phytoestrogens and other secondary metabolites in grazing pastures.

Health risk for humans and animals

As part of the study, representative samples of pastures were collected from 18 Austrian dairy farms (one sample per farm) from April to October 2019 and analysed using high-resolution mass spectrometry after sample preparation. “We frequently detected mixtures of regulated, emerging mycotoxins and phytoestrogens in the pastures that formed part this study. Due to their incorporation into the feed chain, the unpredictable toxicological interactions and the transfer to animal products, these toxin mixtures may implicate a health risk for animals and humans that is likely to increase with global warming and must remain a focus of research,” says study director Qendrim Zebeli, head of the Institute of Animal Nutrition and Functional Plant Compounds at Vetmeduni Vienna.

Study detects 68 harmful substances in Austrian pastures

The study revealed a broad range of mycotoxins, phytoestrogens and secondary metabolites in Austrian pastures with a total of 68 different metabolites. Although the concentrations of individual fungal toxins and metabolites were generally low (often less than 200 µg/kg of dry matter), the total fungal metabolite concentration could reach over 6,000 µg/kg of dry matter in individual pastures. In detail, the data underline Fusarium as the most important fungus in pastures. Nevertheless, the researchers stress that attention should also be paid to possible high levels of ergot alkaloids and Alternaria mycotoxins.

Increasing temperatures as key influencing factor: exponential increase in toxin levels at temperatures above daily mean of 15 °C

The production of fungal and plant secondary metabolites is influenced by multiple biological (species, variety, plant age, parasitic and symbiotic interactions) as well as geoclimatic factors (temperature, relative humidity, rainfall, latitude and altitude). However, environmental temperature proved to be the most influential factor. The number of fungal metabolites increased linearly with increasing temperatures and temperatures exceeding a daily average of 15 °C triggered an exponential increment in the concentrations of Fusarium and Alternaria metabolites and ergot alkaloids. The study’s first author, Felipe Penagos-Tabares from the Institute of Animal Nutrition and Functional Plant Compounds at Vetmeduni, summarizes the findings as follows: “Long-term exposure, along with co-occurrence with modified and emerging mycotoxins, could represent an underestimated risk for grazing and forage-fed animals, even though the levels detected were below EU guidance levels. The data from this study point to a dominant effect of environmental temperature on the diversity and contamination level of toxic fungal metabolites in pastures, revealing that global climate change is also reflected in Austrian pastures.”