SWITZERLAND - Livestock medications can impair beneficial organisms that break down dung, but a new study could show a way to conduct better testing to prevent such harm.
Toxicity of new livestock medications is currently tested with individual animal species such as the common yellow dung fly, the barn fly or a dung beetle, but sensitivity to these substance can vary even between closely related species.
An international research group including University of Zurich evolutionary biologist Wolf Blanckenhorn recently proposed extending the testing scheme to a representative selection of all organisms that break down dung, ideally in their natural environment.
For their feasibility study, the scientists worked on cattle pastures in the Canadian Prairie and the agricultural landscapes of southern France, the Netherlands and Switzerland – four locations with very different climatic conditions.
On these pastures, they distributed dung pats with different concentrations of ivermectin, a common drug used against parasites.
“As expected, the overall number and diversity of dung beetles, dung flies and parasitoid wasps decreased as the ivermectin concentration increased,” explained Mr Blanckenhorn.
However, a number of species also proved to be resistant: earthworms and springtails living in the ground underneath the cowpats were not notably affected, and a parallel test ultimately revealed that dung degradation was not significantly impaired.
“Evidently, beneficial organisms not affected as much by the drug, such as earthworms, were apparently able to compensate for the loss of other organisms,” summed up Mr Blanckenhorn.
The results, which were reproducible across four habitats, may lead the way to developing a more comprehensive test of the toxicity of drugs in the environment.
TheCattleSite News Desk