The Thai Journal of Veterinary Medicine


270, 3-month old, Black Tiger Shrimps (Penaeus monodon) (average 24.55 grams b.w.) were fed for 5 days with oxytetracycline (OTC) medicated feed (coated with squid oil) at 2000 milligrams of OTC per kilogram of feed (2000 ppm). OTC in the hepatopancreas and muscle was measured using High Performance Liquid Chromatography (HPLC) (96 percentage recovery). Samples were taken 0.5, 1, 4, 12 and 24 hours after first administration and 1, 5, 7, 10,14, 21 days after the 5-day treatment. The OTC concentration in samples from fifty negative control shrimps was undetectable by this method. The maximum concentration of OTC (Cmax) detected in the hepatopancreas at 0.5 hours after the initial medication (tmax) was 19.05 ppm, which was greater than the minimal inhibitory concentration 60% (MIC60 = 4 ppm). However, the concentration decreased rapidly to 10.46 ppm and 8.16 ppm, 1 and 4 hours after the initial medication. By the fifth and seventh day, following the cessation of feeding the medicated feed, the drug residue in the shrimps hepatopancreas and muscle, was less than the detectable limits for the method used.

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