Organic acids blend as dietary antibiotic replacer in marine fish olive flounder, Paralichthys olivaceus

The present study was conducted to evaluate the efficacy of organic acid blends as dietary antibiotic replacer in marine fish olive flounder, Paralichthys olivaceus. Fish averaging 3.5 +/- 0.05g (mean +/- SD) were fed one of the four experimental diets: (1) without antibiotic or organic acid (Control/CON); (2) with antibiotic50mg oxytetracycline per kg body weight per day (OTC); (3) with organic acid blend A4g/kg diet (OA(A)); and (4) with organic acid blend B4g/kg diet (OA(B)), for 10weeks. At the end of the experiment, total intestinal bacterial counts in fish-fed OA(A), OA(B) and OTC were significantly lower than that of fish-fed CON diet (p<0.05). Further, the group of fish-fed organic acid blends (OA(A), OA(B)) or antibiotic (OTC)-supplemented diets exhibited lower intestinal Vibrio sp. counts compared with fish-fed CON diet. Disease challenge test with bacteria Edwardsiella tarda showed significantly lower cumulative mortality rates for the group of fish-fed OA(A), OA(B) or OTC than that of fish-fed CON diet (p<0.05). There were no negative effects on the growth, serological characteristics and proximate composition among the group of fish-fed different experimental diets. Therefore, the present experiment demonstrates that blends of organic acid could be a promising alternative to dietary antibiotics for the preventive and/or curative health management in marine fish olive flounder aquaculture.