title: Degradation of abamectin and doramectin on sheep grazed pasture.
abstract: Avermectins are widely used veterinary medicines. They bind strongly to faeces in their non-metabolized form and their half-life in faeces depends on field conditions. There are conflicting data regarding the behaviour of avermectins in the environment. Therefore, we investigated the degradation of abamectin and doramectin on sheep grazed pasture under field conditions in soil, soil-faeces and faeces samples from day 6 to day 70 (abamectin) or to day 50 (doramectin) after sheep treatment. Field conditions were recorded periodically during the experiment. Degradation of abamectin in sheep faeces and in soil-faeces was observed until day 60, with small amounts present in faeces until 70 days post treatment. Because the concentration of abamectin residues in soil was very low on day 6 after treatment, further significant degradation could not be measured. The concentration of doramectin in all analysed matrices decreased rapidly until day 50. It can be concluded that high concentrations of both avermectins were present during the first 20 days after treatment and that field conditions have an important role in degradation of avermectins on grazed pasture of treated animals. Clear identification of the consequences of avermectin exposure and the period of the greatest environmental risk will require further investigations.
authors.affiliation: Institute of Physiology, Pharmacology and Toxicology, University of Ljubljana, Veterinary Faculty, Gerbiceva 60, SI-1000, Ljubljana, Slovenia. nevenka.kozuh@vf.uni-lj.si
authors.forename: Nevenka Kozuh
authors.initials: NK
authors.lastname: Erzen
authors.forename: Lucija
authors.initials: L
authors.lastname: Kolar
authors.forename: Vesna Cerkvenik
authors.initials: VC
authors.lastname: Flajs
authors.forename: Jernej
authors.initials: J
authors.lastname: Kuzner
authors.forename: Irena
authors.initials: I
authors.lastname: Marc
authors.forename: Milan
authors.initials: M
authors.lastname: Pogacnik
mesh_terms: D000818:Animals; D001673:Biodegradation, Environmental; D005243:Feces / Q000737:chemistry*; D007559:Ivermectin / Q000031:analogs & derivatives* / Q000032:analysis; D018570:Risk Assessment; D012756:Sheep; D012988:Soil Microbiology; D012989:Soil Pollutants / Q000032:analysis*; D014887:Weather
chemical_list: D012989:Soil Pollutants; D007559:Ivermectin; C019264:avermectin; C084101:doramectin