Oxytetracycline Levels in Liver and Muscle of Piaractus mesopotamicus after Therapeutic Dosing.

CARRIZO J.C., GRIBOFF J., BACCHETTA C., ROSSI C, CAZENAVE J., SASANYA J., AMÉ M.V.

Montevideo

Congreso; Setac Latin America 15th Biennial Meeting; 2023

Oxytetracycline (OTC) is one of the antibiotics approved for the aquaculture industry in Argentina. However, there is limited information on the uptake, distribution and accumulation of OTC in Piaractus mesopotamicus (Pacú) tissues; a species that has taken great relevance for production in recent years. In the present study, freshwater fish P. mesopotamicus were fed diets containing OTC pure (ATB1) and OTC in a commercial form (ATB2) for 10 days with a withdrawal period of 21 days. A control group, receiving the same diet but without the addition of OTC, was also included. OTC residues were measured at 0, 0.25, 1, 3, 10, 11, and 31 days, by solid phase extraction and Ultra-Performance liquid chromatography system (UPLC) coupled to tandem quadrupole mass spectrometer (MS/MS) using isotopic dilution. OTC was detected in muscle and liver after 0.25 days (6 h) of administration, for both ATB1 and ATB2, showing consistently higher concentrations in liver than in muscle. In the liver, the highest levels were observed at days 1, 3 and 10, without significant differences among them for ATB2. For ATB1, the highest levels in the liver were detected at days 3 and 10. In muscle, the highest OTC concentrations were measured at day 1, for both treatments. During the depuration period, OTC levels decreased in both muscle and liver tissues,reaching after 21 days of withdrawal concentrations below the detection limit in muscle (0.01 μg/kg, wet weight) and below 6 μg/kg w. w. in the liver. The study also showed that the treatment with the commercial form (ATB2) always turned out in higher OTC concentrations compared to the OTC residues after ATB1 treatment. These results could be possibly due to the higher sucrose content in ATB2 increasing the palatability and bioavailability of the food with the antibiotic. In the control group, OTC was detected in both liver and muscle, but at significantly lower concentrations than in treated fish. Our study provides valuable insights into the accumulation and clearance of OTC in Pacú tissues and the potential implications of using commercial OTC in fish farming practices. However, further research is needed to fully understand the long-term effects of OTC on fish health and the potential risks associated with its use in aquaculture.