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.
For use in veterinary sanitary control of foodstuffs and raw materials of animal origin in Slovenia, we developed a routine and confirmation analytical method for determining the residues of enrofloxacin, ciprofloxacin and flumequine in the muscle tissue of cattle, pigs and poultry. For the muscle tissue of freshwater fish, the determination of the flumequine residues was introduced. The results obtained through simultaneous determination of the residues of enrofloxacin, ciprofloxacin and flumequine showed that the values for the examined antibiotics were up to 600 times lower than the prescribed maximum residue levels (MRL). Another advantage of this method is that it covers a wide range of different fluoroquinolones.
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