Accumulation and depletion of oxytetracycline (OTC) and oxolinic acid (OXA) in Pompano, Trachinotus blochii

Accumulation and depletion including withdrawal period for oxytetracycline (OTC) and oxolinic acid (OXA) in pompano (Trachinotus blochii) were determined following oral administration. Pompano were cultured in 250-L fiberglass tanks in a flow-through system provided with aeration. Observed average temperature was 30oC; salinity was 30 ppt. Fish were starved for 2 days then fed with OTC medicated diet (75mg/kg fish/day) or OXA medicated diet (30 mg/kg fish/day) 3 times a day for 10 successive days at 2% body weight and thereafter switched to regular diet for 45 days. Muscle and blood samples were taken at regular intervals during and after cessation of medication. OTC residues in the muscle and blood were analysed using the high performance liquid chromatography (HPLC). Peak OTC accumulation was observed at day 10 of treatment. Higher OTC accumulation was observed in the muscle (0.88+0.27 µg/g) than in the blood (0.3+0.09 µg/ml). OXA accumulation peaked on day 5 of treatment; higher OXA accumulation was observed in the muscle (0.11+0.06 µg/g) compared to blood (0.005+0.0001 ug/ml). Withdrawal period at 30oC for OTC in pompano muscle was 19 days (570 degree-days) and 17 days (510 degree-days) in the blood. For OXA, the withdrawal period in pompano muscle and blood at 30oC temperature was 3 days (90 degree-days).