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The fate of anti-parasitics in manure and manure-applied soils

Data covering the fate and behavior of veterinary medicinal products
(VMP) in manure and manure-applied soils has been significantly
enhanced, thanks to recent research out of Germany.

Data covering the fate and behavior of veterinary medicinal products (VMP) in manure and manure-applied soils has been significantly enhanced, thanks to recent research out of Germany. Robert Kreuzig, with the Braunschweig University of Technology’s Institute of Ecological Chemistry and Waste Analysis in Germany, and a team of researchers have been investigating the fate and behavior of benzimidazole anti-parasitics in manure and manure-applied soils under laboratory and field conditions.

An innovative experimental design for laboratory tests on VMP was developed in order to simulate the real entry route of VMP into soil environments already under laboratory conditions. Degradation tests of VMP as 14C labeled radio-tracers in manures were conducted. Test manures containing seven-day aged VMP residues were prepared and then applied in laboratory batch tests to study degradation and absorption of VMP in soils containing manure. In further tests, the differentiation of microbial, chemical and photo-induced degradation were taken into account. Finally, test plot experiments were performed under field conditions to monitor the transferability of the laboratory data to field conditions.

The benzimidazole anti-parasitics flubendazole and fenbendazole remained mostly extractable in pig manure and soil samples. In contrast, antibiotics, such as sulfonamides, rapidly formed non-extractable residues. Flubendazole was found unchanged while fenbendazole was accompanied by corresponding metabolites. Due to their slow degradation in pig manure, manure storage is not considered to reduce substantially the environmental exposure. As shown by the absorption tests, both benzimidazoles did not fulfill the criteria of potential leachers.

Finally, the degradation tests show the dependence of the metabolic fate on the microbial activity in the soil and on the test manure application. These aspects emphasize that the consideration of manure effects already under laboratory conditions support a better understanding of the environmental fate of VMP under field conditions.

Results from this research project were published in the November 2007 issue of the journal CLEAN – Soil, Air, Water (A Journal of Sustainability and Environmental Safety). The full research article can be viewed at www.clean-journal.com -end-