Organic acids blend as dietary antibiotic replacer in marine fish olive flounder,<i>Paralichthys olivaceus</i>

Abstract

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 ± 0.05 g (mean ± SD) were fed one of the four experimental diets: (1) without antibiotic or organic acid (Control/CON); (2) with antibiotic—50 mg oxytetracycline per kg body weight per day (OTC); (3) with organic acid blend A—4 g/kg diet (OAA); and (4) with organic acid blend B—4 g/kg diet (OAB), for 10 weeks. At the end of the experiment, total intestinal bacterial counts in fish-fed OAA, OAB and OTC were significantly lower than that of fish-fed CON diet (p < 0.05). Further, the group of fish-fed organic acid blends (OAA, OAB) 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 OAA, OAB 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.