Use of Veterinary Pharmaceuticals and Application via Manure Slurries to Soil in the Netherlands

Veterinary Pharmaceuticals (VPs) are used world-wide to cure or prevent illness of animals, and increasingly investigated in view of emissions into the environment. It is known that environmental routes of VPs are complex while transport rates and persistence are not yet well established. Our investigation focuses on the route till application of VPs in (liquid) manure to soil. To characterize this for the Netherlands, we investigated national usage of 4 livestock sectors (dairy cow, veal calf, sow and fattening pig), as well as animal excretion rates prior and degradation during slurry manure storage. This has been done for 12 antibiotics, 4 antiparasitic drugs and one hormone. An inventory of data bases and taking into account data reliability, revealed for almost all substances a reduction of quantities administrated to the animals during the period 2015-2018. Literature review on excretion rates identified that there is still insufficient information, despite that those rates directly influence the VP portions in the environment. Our developed storage model showed that VPs concentrations during a period of 6 months could reduce by a factor as large as 60 and that the fractions present in that manure are highly dependent on animal type, quantity of produced manure and substance degradation rates. At the same time, our predicted after-storage concentrations were found to be comparable with the reported measurements available for some parts of the Netherlands. Considering that similar manure types are applied on arable lands and grasslands in considerable quantities in many other countries, our approach and results may represent a good foundation for further research on the environmental fate of VPs.