Factors influencing dissipation of avermectins in sheep faeces.

Factors influencing fate of avermectins (abamectin, doramectin) in faeces of treated sheep were investigated under different experimental conditions. In the laboratory, concentrations of both avermectins were declined in homogenised faeces of treated animals until day 14 of exposure, regardless of experimental conditions. After that day, no significant decrease in concentrations was observed till the end of the experiment. Established DT(50) did not exceed 9 days. In the karst pasture, an average DT(50) of 27 days was established for abamectin and 23 days for doramectin in natural faeces of treated sheep. In the compost mixture, doramectin concentration was decreased by 38.9+/-2.6% during 21 days of the thermophilic phase of composting. Therefore, DT(50) was not established. A possible influence of moisture content of sheep faeces on concentrations of avermectins was observed.

Time profile of abamectin and doramectin excretion and degradation in sheep faeces.

We studied abamectin and doramectin excretion and their degradation in sheep faeces under field conditions on pasture after a single subcutaneous dose (0.2mg/kg body weight). In the excretion experiment, maximal abamectin concentration (1277 ng/g dry faeces) was detected on day 3, while doramectin concentration showed two peaks (2186 and 1780 ng/g dry faeces on days 2 and 5, respectively). Both avermectins were excreted at approximately the same rate (k=0.23 day(-1) for abamectin and 0.19 day(-1) for doramectin). In the field, a rapid loss of abamectin and doramectin from sheep faeces was seen during the first 32 days after which concentrations remained constant at approximately 77 ng/g and 300 ng/g, respectively. The half life values (DT(50)) for abamectin and doramectin dissipation from sheep faeces were 23 and 22 days, respectively, during the first 32 days. Dissipation of both avermectins was strongly correlated with moisture content of the faeces.

Degradation of abamectin and doramectin on sheep grazed pasture.

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.

Introduction of the HPLC method for the determination of quinolone residues in various muscle tissues.

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.

Evidence of organochlorine pesticide and polychlorinated biphenyl residues in Slovenian poultry tissues from 1997 to 1999.

The contamination of poultry tissues by total organochlorine (OC) pesticides and polychlorinated biphenyls (PCBs) in Slovenia was examined from a public health perspective. As part of systematic veterinary and sanitary monitoring of foods of animal origin from 1997 to 1999, 87 samples of fat tissue were examined for the presence of alpha-HCH, lindane, heptachlor, and total DDT (plus DDE and DDD) and 88 samples of fat tissue were examined for the presence of total PCBs (sum of PCB congeners). The levels of poultry tissue contamination in six regions of Slovenia were determined. Levels of OC pesticides were below detection limits in 86.2% of analyses performed. Total PCB levels for most samples (59.1%) of poultry fat tissue were in the 0.002- to 0.02-mg/kg range. The level of contamination with OC pesticides and total PCBs in poultry fat tissue was not influenced by the type of poultry and was the highest in samples from industrial areas, which have been ecologically disturbed. All samples met Slovenian and European Union tolerances.