CAJ | 학술논문

Objective: To assess the effects of a widely used antibiotic, oxytetracycline (OTC) on the bacterial microflora in two catfish species under artificial culture conditions in the laboratory. <br> Methods:The experiment was conducted in the Faculty of Fisheries, Bangladesh Agricultural University, Mymensingh-2202. The fish were reared in six aquaria (size 37 cmí30 cmí60 cm) where three aquaria served as replicates of the antibiotic treatment groups and the remaining three aquaria served as an untreated control group. Each aquarium was stocked with 25 fish on an average body weight 15 g. OTC was administered to the fish in the treatment groups at the rate of 2 g/kg in-feed twice daily upto ad libitum, whereas fish in the untreated control groups were given the same feed without antibiotics for 20 d. During the experiment, bacterial loads were estimated as colony forming unit (CFU/g) by every alternate day in the aquarium water, gills, skin and intestine of fish. <br> Results:The administration of OTC in feed resulted in gradual decrease of bacterial loads in the gills, intestine and skin of the two catfish species tested. In contrast, the bacterial loads remain unchanged or slightly increased in the control groups not fed with OTC. Water quality parameters such as dissolved oxygen, pH and total hardness were found to be within suitable range in the test aquaria but not in control aquarium throughout the experimental period. <br> Conclusions:The results of this experiment showed that in-feed antibiotic OTC for a period of 20d reduced the bacterial loads in the gills, intestines and skin of treated fish.