Multi-class and multi-residue analyses are very complex procedures because of the physico-chemical properties of veterinary drug residues and other contaminants. The purpose of the study was to develop an analytical method for the sensitive determination of 69 analytes in bovine milk by liquid chromatography electrospray ionisation–tandem mass spectrometry. Antimicrobial, anabolic hormone, lactone, β-agonist, mycotoxin and pesticide residues were analysed in 120 raw milk samples from different dairy farms in North Macedonia. Stable isotopically labelled internal standards were used to facilitate effective quantification of the analytes. The linear regression coefficients were higher than 0.99, the limits of detection ranged from 0.0036 to 47.94 μg/L, and the limits of quantification ranged from 0.053 to 59.43 μg/L. The decision limit values ranged from 0.062 to 211.32 μg/L and the detection capability from 0.080 to 233.71 μg/L. Average recoveries of the analytes spiked in raw milk were in the range of 70.83% to 109%, intra-day coefficient of variation (CV) values from 2.41% to 22.29%, and inter-day CV values from 3.48% to 23.91%. The method was successfully applied in the testing of bovine milk samples. In five samples residues were detected. They were sulfadimethoxine (in two samples), enrofloxacin, tetracycline and oxytetracycline and were at concentrations below the EU maximum residue limit. The method is useful for routine testing for this group of chemical hazards in bovine milk.

Amitraz is a formamide exhibiting both acaricidal and insecticidal activity and is frequently used by beekeepers to protect honeybee colonies against Varroa destructor mites. The aim of this apiary trial was to evaluate the impact of honeybee colony fumigation with amitraz on the level of contamination of honey stored in combs. Experimental colonies were fumigated four times every four days with one tablet of Apiwarol per treatment. Honey was sampled from combs of brood chambers and combs of supers one day after each amitraz application and from harvested honey. Amitraz marker residues (as a total of amitraz and metabolites containing parts of molecules with properties specific to the 2,4-DMA group, expressed as amitraz) were evaluated in honey. All analysed samples were contaminated with amitraz metabolites. 2,4-DMA and DMPF were the most frequently determined compounds. The average concentration of amitraz marker residue in honey from groups where a smouldering tablet was located directly in beehives was significantly higher than that of residue in honey from groups with indirect smoke generation. No significant effect on the honey contamination deriving from the place where it was exposed to smoke (combs of brood chambers and supers) was noted. Amitraz marker residues exceeded the MRL in 10% of honey samples from combs. Fumigation of beehives with amitraz results in contamination of honey stored in combs.

Introduction: There are many veterinary products containing β-lactam antibiotics which are used for mastitis treatment in cows. The aim of the study was to determine whether mastitis could have any effect on amoxicillin (AMX) or penicillin G procaine (PEN) withdrawal period from milk, in the context of current maximum residue limits established by the European Commission. Material and Methods: The study was conducted on 17 dairy Black and White cows with clinical mastitis during the lactation period. The first group (n = 8) received 200 mg of amoxicillin (AMX), whereas the second group (n = 9) received 200,000 IU/mg of penicillin G procaine (PEN) by intramammary administration. For the measurement of AMX and PEN concentrations in milk, the liquid chromatography tandem mass spectrometry method was applied. Pharmacokinetic calculations were performed using Phoenix WinNonlin 6.4 software. Results: The determined AMX and PEN half-life values in the mammary gland suggest that the drug withdrawal is at a level of 99.9% within 81 h (≈3.5 days) and 116 h (≈5 days) after administration of AMX and PEN, respectively. The present research indicates that, at 60 h after administration, the average PEN concentration in the milk from cows with clinical signs of mastitis may still reach 4.96 g/kg and that of AMX can even be 6.92 g/kg. Conclusion: The results obtained confirm that, in mastitis cases, a 72-h withdrawal period is sufficient for elimination of AMX to a lower level than the established maximum residue limit (MRL) values. However, in the case of PEN, at 69 h after administration, the drug concentration may be close to that of the determined MRL.

An 8-month-old 3.15 kg female Cocker-spaniel with history of ataxia referred to the Veterianary Medical Teaching Hospital, Chungnam National University. There were no abnormalities in CBC and serum chemical analysis. Agenesis of dens was found on dorsoventral view in cervical radiography. Compressed cervical spinal cord and enlarged cerebral ventricle were observed in magnetic resonance imaging. It was diagnosed as atlantoaxial instability with hydrocephalus.

Healthy gilts and market-ready hogs were administered a single intramuscular (IM) injection of Borgal, a commercial formulation of trimethoprim-sulfadoxine (TMP-SDX), once or twice daily. The objectives were to determine if a newly-developed high-performance liquid chromatographic (HPLC) method would be suitable for measuring the residual concentrations of TMP in the plasma of these live animals, and to determine if the administration of this veterinary drug would leave measurable residues in their plasma and tissues at slaughter. Plasma and tissue concentrations of SDX and TMP from these animals were determined over a period of 14 d using thin-layer chromatography/densitometry (TLCD), and the newly-developed HPLC method, respectively. The lowest detectable limit (LDL) for SDX in plasma and tissue was 20 ppb by TLCD. The HPLC method had a LDL of 5 ppb for TMP in plasma and tissue. Both methods were then used to provide baseline data on the absorption and depletion of TMP and SDX from these healthy animals. It was observed that both TMP and SDX were readily absorbed into the blood and tissues, but TMP was eliminated much faster than SDX. No TMP residues were detected in the plasma of any of the gilts at and beyond 21 h after drug administration. Also, no TMP residues were detected in the plasma of any of the market-ready hogs 24 h after drug administration at either the label dose or twice the label dose. Sulfadoxine residues at concentrations above the maximum residue limit (MRL) of 100 ppb were, however, detected in the plasma, muscle, kidney, liver, and injection sites of hogs slaughtered 1 and 3 d after a single IM administration at the label dose. Although SDX residues were still detectable in the lungs, kidney, liver and plasma of some hogs 10 d after administration of the label dose and twice the label dose, these were below the MRL. Postmortem examination revealed necrosis and inflammation at the injection sites, but no visible deposits of the injected drug.