In The Netherlands, all antibiotic treatments should be registered at the farm and in a central database. To enforce correct antibiotic use and registration, and to enforce prudent use of antibiotics, there is a need for methods that are able to detect antibiotic treatments. Ideally, such a method is able to detect antibiotic applications during the entire lifespan of an animal, including treatments administered during the first days of the animals’ lives. Monitoring tissue, as is common practice, only provides a limited window of opportunity, as residue levels in tissue soon drop below measurable quantities. The analysis of feathers proves to be a promising tool in this respect. Furthermore, a qualitative confirmatory method was developed for the analyses of six major groups of antibiotics in ground chicken feathers, aiming for a detection limit as low as reasonably possible. The method was validated according to Commission Decision 2002/657/EC. All compounds comply with the criteria and, as a matter of fact, 58% of the compounds could also be quantified according to regulations. Additionally, we demonstrated that a less laborious method, in which whole feathers were analyzed, proved successful in the detection of applied antibiotics. Most compounds could be detected at levels of 2 μg kg⁻¹ or below with the exception of sulfachloropyridazine, tylosin, and tylvalosin. This demonstrates the effectiveness of feather analysis to detect antibiotic use to allow effective enforcement of antibiotic use and prevent the illegal, off-label, and nonregistered use of antibiotics.

Monitoring strategies for veterinary drugs in products of animal origin are shifting towards a more risk-based approach. Such strategies not only target a limited number of predefined .substances but also facilitate detection of unexpected substances. By combining the use of archive matrices such as feather meal with suspect-screening methods, early detection of new hazards in the food and feed industry can be achieved. Effective application of such strategies is hampered by complex data interpretation and therefore, targeted data analysis is commonly applied. In this study, the performance of a suspect-screening data processing workflow using a suspect list or the online spectral database mzCloud^TM was explored to facilitate detection of veterinary drugs in archive matrices. Data evaluation parameters specifically investigated for application of a suspect list were mass tolerance and the addition or omission of retention times. Application of a mass tolerance of 1.5 ppm leads to an increase in the number of false positives, as does omission of retention times in the suspect list. Different acquisition modes yielding different qualities of MS2 data were studied and proved to be a critical factor, where data-dependent acquisition is preferred when matching to the mzCloud^TM database. Using this approach, it is possible to search for compounds on a dedicated suspect list based on the exact mass and retention times and, at the same time, detect unexpected compounds without a priori information. A pilot study was conducted and fourteen different antibiotics were detected (and confirmed by MS/MS). Three of these antibiotics were not included in the suspect list. The optimised suspect-screening method proved to be fit for the purpose of finding veterinary drugs in feather meal, which are not in the scope of the current monitoring methods and therefore, it gives added value in the perspective of a risk-based monitoring.

Background/Objectives: This study aimed to understand the extent of transmission of antibiotic residues from treated to untreated pigs and the barn environment using different pen set-ups. This is in order to create awareness and to stimulate prudent use of antibiotics in livestock farming. Methods: Transmission, expressed as the (relative) residue level, of sulfadimidine, enrofloxacin and its metabolite ciprofloxacin was determined using animal wipes, surface wipes and manure samples of pigs in four different compartments with variations in interconnected or distanced pens and type of pen partitions (open or closed). Results: Most antibiotic residues in untreated pigs were detected with a combination of open partitions and interconnected pens. Separating the pens with space in between minimized detectable antibiotic residues in the manure of untreated pigs, whereas interconnected pens did show antibiotic residues in internal matrices. Antibiotic residues were detected in the barn environment after treatment in all different pen set-ups. Conclusions: After treatment, transmission of antibiotic residues occurred in the barn environment and in the untreated pigs housed in the same barn. The spatial distribution of residues suggests that airborne dust and/or aerosols may be important routes of external transmission. Results under these experimental conditions indicate that restricting physical contact between treated and untreated pigs may be an important strategy for reducing antibiotic residues in internal matrices. This set-up also showed lower external residue levels, especially when closed partitions are used.