Faculty of Veterinary Medicine

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Depletion of [3H] amitraz in sheep
(Springer Science and Business Media LLC, 2025-12-24)
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Jovanovski, Stefan
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Janevski, Aleksandar
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Musliu, Dea
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High-Performance Liquid Chromatography with DAD Detection for the Determination of Cannabinoids in Commercial Veterinary CBD Oil
(MDPI AG, 2024-12-02)
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Dimitreska Stojkovikj, Elizabeta
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Gusheski, Dimitar
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Musliu, Dea
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Velkovski, Daniel
The study highlights the need for quality control in evaluating medicinal plant products, especially CBD oils, before market release. Due to varying regulatory requirements, product labeling can sometimes be misleading, especially regarding cannabinoid concentrations such as CBD and THC. This research focused on developing a validated high-performance liquid chromatography (HPLC) method for accurately identifying and quantifying key cannabinoids in Commercial Veterinary CBD Oil. The main compounds identified included Cannabidivarin (CBDV), Cannabidiolic Acid (CBD-A), Cannabigerolic Acid (CBG-A), Cannabigerol (CBG), Cannabidiol (CBD), Tetrahydrocannabivarin (THCV), Cannabinol (CBN), ∆9-Tetrahydrocannabinol (d9-THC) ∆8-Tetrahydrocannabinol (d8-THC), Cannabicyclol (CBL), Cannabichromene (CBC), and Tetrahydrocannabinolic Acid (THCA), determined in line with the International Conference on Harmonization’s (ICH) guidelines. The method was validated for linearity, accuracy, precision, limit of detection (LOD), and limit of quantitation (LOQ). It was determined to be linear, with a correlation coefficient (R²) > 0.999. The LOD and LOQ values calculated from the calibration curve ranged from 0.05 to 0.13 and 0.50 to 0.61 µg/mL, respectively. The method also exhibited acceptable precision, with relative standard deviation values lower than or equal to 2%. The method’s accuracy was assessed through recovery percentages and fell within an acceptable range of 98–102 if the RSD was 2%. This study’s rigorous methodology and comprehensive findings significantly contribute to cannabinoid analysis. This validated protocol was used to analyze cannabinoids in 14 commercial veterinary CBD oil products from the Republic of North Macedonia. The performance parameters demonstrated that the method is reliable for quantitatively measuring cannabinoids in CBD oil. The analysis showed that the cannabinoid levels in the products were consistent with the manufacturers’ declared specifications, with no significant discrepancies in labeling.
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Monitoring Heavy Metals, Mycotoxins, Coccidiostats and Microbial Contamination in Animal Feed: A North Macedonia Study (2018-2022)
(Walter de Gruyter GmbH, 2025-06-24)
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Enimiteva, Vangelica
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Angelovski, Ljupco
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Feed contamination can occur at every stage of the feed chain, including manufacturing, storage, transport, and utilization. Ensuring feed safety is fundamental for livestock health, animal performance, and food safety throughout the feed-to-food chain. The study aimed to make qualitative and quantitative assessment of microbiological and chemical hazards in animal feed in North Macedonia from 2018 to 2022. A total of 1,629 feed samples were analysed for heavy metals, mycotoxins, and coccidiostats, whereas 598 samples were examined for microbial contamination. The results indicate a significant prevalence of heavy metals, with lead (Pb) detected in 100% of the samples, although mostly within regulatory limits. Mycotoxins, notably ochratoxin A (OTA) and aflatoxin B1 (AFB1), were also identified, with non-compliance in 10.88% of cattle feed for AFB1. Coccidiostat residues exceeded the maximum levels in 4.6% of the samples. Microbiological analysis revealed that 1.34% of feed samples were contaminated with Salmonella spp., and 3.8% tested positive for sulphitereducing clostridia. The findings on both microbiological and chemical hazards indicate their potential to threaten the feed safety chain. Accordingly, this study emphasizes the need for continuous comprehensive feed safety monitoring and the enforcement of stringent safety regulations to safeguard animal and public health in North Macedonia.
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Multi-class analysis of antimicrobial substances in poultry feed at cross-contamination levels by UHPLC-MS/MS – Method establishment, validation, and application
(Society of Chemists and Technologists of Macedonia, 2025-12-24)
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Koceva, Dushica
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Angjeleska, Aleksandra
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Stojković, Goran
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The Commission Delegated Regulation (EU) 2024/1229 establishes maximum limits (MLs) for the cross-contamination of antimicrobial substances in feed intended for food-producing animals. This study presents the development and in-house validation of two multi-class analytical methods for detecting antimicrobial substances in poultry feed at cross-contamination levels, using ultra-high-performance liquid chromatography coupled with tandem mass spectrometry (UHPLC-MS/MS). Methods with and without solid-phase extraction (SPE) purification were developed for 26 antimicrobial substances across eight classes, covering a concentration range of 5–300 μg kg–1. The methods were validated for parameters in-cluding selectivity, limit of quantification, within- and between-day precision, accuracy, decision limit, matrix effect, and short-term analyte stability in the corresponding extracts. Both methods met the required performance criteria for detecting antimicrobial substances at cross-contamination levels, except for reduced sensitivity to lincomycin in the SPE method. Between-day precision was below 18 % and 19 %, with recoveries ranging from 95 to 103 %, for the method without SPE, and from 88 % to 101 % for the method with SPE, respectively. The analytes remained stable after two days of storage in the dark un-der two temperature conditions. These methods were applied to 39 poultry feed samples, revealing that approximately 41 % contained one or more antimicrobial substances, some of which exceeded the cross-contamination MLs. This study underscores the importance of simple, rapid, sensitive, and reliable analytical methods for controlling the presence of antimicrobials at cross-contamination levels. Such methods enable stringent control to prevent uncontrolled antimicrobial use in poultry production systems, thereby mitigating the development of antimicrobial resistance.
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Systematic multi-year surveillance of honey compliance and fraud in North Macedonia, 2020–2024
(Springer Nature, 2026-02-20)
Nestorovski Tome
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Jovanov Stefan
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Trajkovska Melita J.
Honey adulteration represents a significant food safety and economic concern globally, yet comprehensive data from North Macedonia remains lacking. This study evaluated 538 honey samples (391 domestic, 147 imported) collected between 2020 and 2024 for compliance with national and EU quality standards. Overall, 9.48% of samples failed at least one quality parameter, with domestic honey showing higher non-compliance (12.53%) than imported (1.4%). The primary causes of non-compliance were elevated hydroxymethylfurfural (64.7%) and reduced diastase activity (43.1%), indicating heat-related exposure. Among 16 samples failing C4 sugar analysis, 7 (43.8%) met all other regulatory requirements, suggesting sophisticated adulteration methods that evade routine testing. Statistical analysis revealed very strong associations between heat-related parameters. Temporal analysis showed declining overall non-compliance but increasing prevalence of diastase-related failures. These findings, representing the first systematic assessment of honey adulteration in North Macedonia, indicate that while basic market surveillance appears effective, current testing protocols may miss economically motivated adulteration. Implementation of routine C4 sugar analysis, particularly for samples passing conventional parameters, is essential for comprehensive fraud detection and consumer protection.
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Cleaning and Management of Water Contaminated with Pesticides through the Process of Adsorption in the Natural Clay of Brari
(Polskie Towarzystwo Inżynierii Ekologicznej (PTIE) – Polish Society of Ecological Engineering, Politechnik, WNGB Wydawnictwo Naukowe – WNGB Scientific Publishing Housea Lubelska – Lublin University of Technology,, 2024-01-01)
Esad, Behrami
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Isak Berbatovci
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Kledi Xhaxhiu
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Nensi Isak
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Adelaida Andoni
This study aimed to investigate the potential for widespread application of clay in the purification of water pol luted with pesticides and water management through the absorption and desorption of dimethoate and methomyl in the natural clay of Brari (Tirana). While the maximum adsorption of methomyl on Brari clay was reached in 12 hours, the maximum adsorption of dimethoate on Brari clay was reached in 48 hours. To compare the adsorption of methomyl and dimethoate on Brari clay, their water degradation time was also taken into account. Dimethoate dissolves quickly; a contact period of 1–2 hours is sufficient to desorb 81.2% of the material. Dimethoate dissolves in water at 25 °C and has a half-life t1/2 = 30 days. Methomyl is desorbed even faster; in just two hours, 96.2% of the material is desorbed. At 25 °C, dimethoate has a half-life of t1/2 = 14 days and a high solubility of 58 g/L in water. Because methomyl and dimethoate bind poorly to clay, they can contaminate surface and groundwater.
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TOTAL PHOSPHORUS QUANTIFICATION IN ANIMAL FEED, MILK, MEAT AND THEIR PRODUCTS USING THE ISO 13730:1996 METHOD
(Faculty of Veterinary Medicine - Skopje, 2024-09-22)
Tome Nestorovski
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Stefan, Jovanov
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Phosphorus is a macro-element naturally present in animal feed, meat, milk and their products. Due to its beneficial properties, it is also used as an additive in these food groups. Monitoring total phosphorus concentrations in all food and feed products, whether it occurs naturally or is added during processing, is crucial for health safety. A high and unregulated intake of phosphorus can lead to side effects such as cardiovascular and kidney diseases as well as other complications in both humans and animals. The aim of this study was to integrate the phosphorus quantification method for animal feed described in ISO 6491:1998, into the previously optimized spectroscopy conditions for total phosphorus quantification in both meat and milk food matrices as a continuation of the research. The proficiency test results, with assigned value of 5870 mg / kg yielded a Z – score of - 0.3. Following this, the method was verified by determining the standard deviation (SD) for each sample series, the repeatability (r), and the expanded uncertainty (U). The results have confirmed that the conditions of the ISO 13730:1996 method are suitable for accurately quantifying total phosphorus content in all animal feed, meat and milk matrices. This unification contributes to reducing the cost and time required for performing the analysis, and ensures excellent precision in quantifying total phosphorus content, thus expanding the scope of application.
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DETERMINATION OF COMONLY USED ARTIFICIAL COLORS IN MEAT AND MEAT PRODUCTS USING HPLC-DAD METHOD
(Faculty of Veterinary Medicine - Skopje, 2024-09-22)
Stefan, Jovanov
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Tome Nestorovski
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The color of the meat is the most crucial visual quality parameter from the consumer's perspective. Red color additives are used to improve the appearance of meat and meat products on the shelf. Although natural colors like red wine or beet juice are used, there are artificial colors which can withstand the temperature and pH conditions of processing. According the Food additive Regulation in North Macedonia, Carmoisine (Azorubine), Allura Red, Ponceau 4R and Carminic Acid are permitted for use. The allowed limits of these colors in meat and meat products range from 25 mg/kg to 200 mg/kg depending on the additive and whether the meat product is heat treated or not. The aim of this study is to develop a HPLC-DAD method to determine these additives in meat and meat products. Due to the different chemical properties of carminic acid compared to the others, two different HPLC-DAD methods with different sample preparation were developed. Both used RP C18 column and gradient elution with methanol and phosphate buffer, but with different pH levels. Method validation was performed according to ICH Harmonised Guideline Q2(R2) (2022). The method was validated in terms of linearity, accuracy, precision, limit of detection (LOD), and limit of quantitation (LOQ), and found to be linear, with a correlation coefficient (R2) ranging from 0.995 to 0.999. The LOD and LOQ values calculated from the calibration curve ranged from 0.10 to 0.23 mg/kg and 1.00 to 1.12 mg/kg respectively. The accuracy of the method was evaluated based on the recovery percentages at 3 spiked levels (1, 5 and 10 mg/kg), which were found to be within an acceptable range of 93.82 to 109.30%. The repeatability of the method was assesed at the same three spiking levels over two days, with relative standard deviation (RSDR) values ranging from 2.01 % to 4.97 %. These performance parameters indicate that the developed and validated method is suitable for the quantitative determination of Carmoisine (Azorubine), Allura Red, Ponceau 4R and Carminic Acid in meat and meat products. Random meat products analysis using this method revealed that 15 out of 55 contained these additives but none exceeded the legislative limits
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A STUDY ON THE PRESENCE OF SOME HEAVY METALS AS FEED ADDITIVES IN ANIMAL NUTRITION IN THE REPUBLIC OF NORTH MACEDONIA
(Faculty of Veterinary Medicine - Skopje, 2024-09-22)
Vangelica, Enimiteva
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Dushica, Koceva
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Aleksandra, Angeleska
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Essential heavy metals Mn, Co, Cu, and Zn are important in livestock production in trace amounts due to their physiological functions such as hormone synthesis, oxygen and electron transportation, fertility, antioxidant defense, and immunity. However, their presence beyond a certain limit in the biological system potentiates toxicity and provokes adverse effects in animals. These metals are administered by feed, where they are added in the form of chelates or organic compounds. In the European Union, Mn, Co, Cu, and Zn utilization in animal nutrition is ruled by Regulation (EC) No. 1831/2003. So far, there is no data on the presence of metals as feed additives in the nutrition of livestock in North Macedonia. As a result, this study aimed to determine the levels of Mn, Co, Cu, and Zn in complete feeds and evaluate their amounts relative to the maximum permitted levels under the legislation mentioned above. Between May 2023 and April 2024, we collected 109 complete feed samples, including 37 for cattle, 33 for pork, and 39 for poultry, from farms and feed distributors in North Macedonia. Samples were analyzed according to EN 15763:2009 with inductively coupled plasma-mass spectrometry (ICP-MS), after microwave-assisted mineralization. We performed the method validation following the ICH Q2 Guideline. The average determined levels of Mn, Co, Cu, and Zn are 0.440, 0.367, 1.648, and 0.524 mg/kg, respectively. The maximum determined amounts are 0.969 mg/kg for Mn, 0.698 mg/kg for Co, 7.160 mg/kg for Cu, and 3.562 mg/kg for Zn. We observe no violation of the maximum permitted levels; however, we must consider some precautions regarding the Co content, as the average concentration hovers around 37%, and the maximum 70% of the permitted level sat at 1 mg/kg. Regarding Mn, Cu, and Zn, the determined average and maximal concentrations are far below the maximum permitted levels. In conclusion, the determined levels of Mn, Co, Cu, and Zn within this study pose no risk to the health of the food-producing animals. Moreover, the presence of the aforementioned metals in animal nutrition is not of concern for the environment, provided that their maximum permitted levels are respected.
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Multi-class/residue method for determination of veterinary drug residues, mycotoxins and pesticide in urine using LC-MS/MS technique
(Springer Science and Business Media LLC, 2023-09-14)
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Jovanov, Stefan
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Musliu, Dea
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Background Veterinary drugs are widely used in animals to prevent diseases and are a complex set of drugs with very different chemical properties. Multiclass and multi-residue methods for simultaneous detection of residues from veterinary drugs and contaminants in urine are very rare or non-existent. Therefore, the aim of this study was to develop and validate a sensitive and reliable quantitative LC-MS/MS method for simultaneous determination of a wide range of veterinary drug and pesticide residues and mycotoxins in bovine urine. This involved 42 veterinary drug residues (4 thyreostats, 6 anabolic hormones, 2 lactones, 10 beta agonists, 15 antibiotics, 5 sulphonamides), 28 pesticides and 2 mycotoxins. Stable isotopically labelled internal standards were used to facilitate effective quantification of the analytes. Analysis was performed in both positive and negative ionization modes with multiple reaction monitoring transitions over a period of 12 min. Results The parameters validated included linearity, limit of detection (LOD), limit of quantification (LOQ), detection capability (CCβ), decision limit (CCα), stability, accuracy and precision. The process followed guidelines of the regulation 2021/808/EC. The calibration curves were linear with coefficient of correlation (R2) from 0.991 to 0.999. The LODs were from 0.01 to 2.71 µg/L, while the LOQs were from 0.05 to 7.52 µg/L. The CCα and CCβ were in range 0.05–12.11 µg/L and 0.08–15.16 µg/L. In addition, the average recoveries of the spiked urine samples were from 71.0 to 117.0% and coefficient of variation (CV) < 21.38% (intraday and interday). Conclusion A new isotopic LC-MS/MS method has been developed, validated and applied for identification and quantification of 72 residues of veterinary drugs and pesticides and other contaminants such as mycotoxins in bovine urine. The most appropriated sample preparation procedures involved sodium acetate buffer, enzymatic hydrolysis using β-glucuronidase and cleanup solid phase extraction with OASIS SPE cartridges. The parameters were satisfactorily validated fulfilling requirements under Regulation 2021/808/EC. Consequently, the method could be used in routine analysis of bovine urine samples for simultaneous detection of veterinary drug and pesticide residues as well as contaminants such as mycotoxins.

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