EFFECT OF TEMPERATURE AND DIET COMPOSITION ON RESIDUE DEPLETION OF OXYTETRACYCLINE IN CULTURED CHANNEL CATFISH

Oxytetracycline is an antibacterial agent widely used in fish farming. The normal method of administration of oxytetracycline to the fish is to mix the drug into the feed. As a consequence, the concentration of the drug in feed, together with the preparation and the composition o f feed, can influence the disposition of the drug itself. An experimen tal study was carried out to evaluate the residue depletion of oxytetr acycline from muscle tissue of channel catfish (Ictalurus punctatus) f ed different medicated diets. Three hundred channel catfish were rando mly divided into six tanks (50 fish per tank), maintained at water tem peratures of 18 degrees C (three tanks) and 23 degrees C (three tanks) . The animals were fed with three diets, differing in their energy con tent and composition, for the duration of the experiment oxytetracycli ne was added to the diets at a level of 7500 mg kg(-1) for 7 d. After cessation of the treatment, five fish from each tank were killed on da ys 1, 3, 8, 13, 18, 24, 30, 35 and 40. Oxytetracycline residues in mus cle tissue were determined by high-performance liquid chromatography. The results indicate that the energy level and chemical composition of the medicated diets administered to channel catfish influence oxytetr acycline disposition in fish, and that temperature is an important fac tor in conditioning the reported dietary effects. Therefore, formulati on of specific diets to administer drugs to farmed fish could assure b etter bioavailability of the chemotherapeutant and shorter withdrawal times.