Tissue Distribution and Elimination of Oxytetracycline in Sea-Pen Cultured Chinook Salmon, Oncorhynchus tshawytscha, and Atlantic Salmon, Salmo salar, Following Medicated-Feed Treatment

ABSTRACT

Oxytetracycline (OTC) tissue distribution and elimination by sea water salmon were studied using seapen-cultured chi-nook salmon, Oncorhynchus tshawytscha, and Atlantic salmon, Salmo salar. Chinook salmon were treated with OTC-medicated feed at a rate of 100 mg OTC/kg body weight per day for 10 days in 9°C or 12°C sea water. Atlantic salmon were treated by the same medicated feed and dosage in 7,2°C sea water. At specific time points, 3 or 6 salmon were removed from each sea-pen, sacrificed, and analysed for OTC with HPLC. OTC concentration profiles in chinook salmon tissues were found to be very similar to those of the Atlantic salmon. Tissue OTC concentrations in the salmonids generally decreased in the order of liver>kidney>skin>muscle at the end of the treatment period. The elimination of OTC from the muscle of chinook salmon was markedly affected by water temperature; the half-lives t\a of OTC elimination from the muscle were 13.59 days and 10.34 days at 9°C and 12°C, respectively. The t\a of OTC elimination from the muscle of Atlantic salmon was 15.75 days at 7.2°C. These results show that the pharmacokinetics of OTC in Atlantic and chinook salmon are very similar afterperos administration. As a result, OTC pharmacokinetics obtained from a chinook salmon study can be used for dosage adjustment and withdrawal time determination in Atlantic salmon and vice versa