Porcine Oral Fluid as a Diagnostic Matrix for Tulathromycin and Enrofloxacin Residue Surveillance

Antibiotic analysis is an important aspect of pig farming due to residues in tissues and the spread of antimicrobial resistance. In vivo control of antimicrobials is particularly significant, especially for the most critical and widely administered drugs. Thus, the aim of this study was to investigate the concentrations of tulathromycin and enrofloxacin in oral fluid after pig treatment. The analysis was performed by an ultrahigh-performance liquid chromatography with tandem mass spectrometry (UHPLC-MS/MS) method. Both drugs were detected for 31 days after the end of the treatment. On the last day of sampling, the concentration of tulathromycin was 19.7 μg/L and that of enrofloxacin was 26.4 μg/L. Tulathromycin reached its peak concentration (2180 μg/L) on day 2, while the highest concentration of enrofloxacin (1250 μg/L) was recorded on day 1 postadministration. The obtained results confirm the feasibility of detecting the two tested compounds in oral fluid, demonstrating a new approach for antemortem antibiotic control in pigs.