The fate of ivermectin (IVM) residues was studied throughout the processing of daily bulk milk from 30 ewes (taken up to 33 d following subcutaneous administration of 0 . 2 mg IVM/kg b.w.) in the following milk products: yoghurt made from raw and pasteurized milk; cheese after pressing ; 30-and 60-day ripened cheese; and whey, secondary whey and whey proteins obtained after cheese-making (albumin cheese). The concentration of the H 2 B 1a component of IVM was analysed in these dairy products using an HPLC method with fluorescence detection. The mean recovery of the method was, depending on the matrix, between 87 and 100%. Limits of detection in the order of only 0 . 1 mg H 2 B 1a /kg of product were achieved. Maximum concentrations of IVM were detected mostly at 2 d after drug administration to the ewes. The highest concentration of IVM was found on day 2 in 60-day ripened cheese (96 mg H 2 B 1a /kg cheese). Secondary whey was the matrix with the lowest concentration of IVM (< 0 . 6 mg H 2 B 1a / kg). Residue levels fell below the limits of detection between day 5 (for secondary whey) and day 25 (for all cheese samples). In the matrices investigated, linear correlations between daily concentrations of IVM, milk fat and solid content were evident. During yoghurt production, fermentation and thermal stability of IVM was observed. During cheese production, approximately 35 % of the IVM, present in the raw (bulk) milk samples, was lost. From the results it was concluded that the processing of ewes' milk did not eliminate the drug residues under investigation. The consequences of IVM in the human diet were discussed. Milk from treated animals should be excluded from production of fat products like cheese for longer after treatment with IVM than for lower fat products.
This paper describes the results of investigation into the concentrations of lead and cadmium in tissues of pigs and cattle from slaughterhouses in Slovenia in the period between 1989 and 1993. Analyses were performed by flame atomic absorption spectrometry. Quality assurance was carried out by analysis of certified reference materials and recovery tests. The mean concentrations of lead in bovine meat, liver and kidney were 0.05, 0.10 and 0.14 mg/kg wet weight and those in the corresponding pig tissues were < 0.05, 0.06 and 0.06 mg/kg wet weight. The mean cadmium concentrations in bovine meat, liver and kidney were 0.004, 0.094 and 0.373 mg/kg wet weight, respectively, while those in the corresponding pig tissues were 0.010, 0.088 and 0.393 mg/kg wet weight. The majority of tissues analysed corresponded to our valid tolerances for both elements, which had not been the case in the previous 5 year period. The agreement with tolerances was to be expected because in 1990 the Veterinary Directorate of Slovenia prescribed a directive on the basis of which kidneys of cattle older than 5 years and pigs older then 2 years should be regarded as unfit for human consumption.
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