Evaluation of the optimum dietary processed sulfur (Immuno-F) level to replace antibiotic (OTC) in juvenile olive flounder, Paralichthys olivaceus

Abstract

치어기 넙치에 있어서 항생제 (OTC)를 대체하기 위한 법제유황 (Immuno-F)의 적정 수준을 평가하기 위하여 8주간 실험을 수행하였다. 실험어는 평균 무게 12.6 ± 0.17 g (mean±SD)인 넙치를 대상으로 3반복으로 한 수조당 20 마리씩 사육하였다. 실험사료는 항생제 및 항생제 대체물질인 법제유황의 첨가수준(단위 ppm)에 따라 총 8개 실험구(Cont, F25, F50, F250, F500, F1000, F2000, OTC4000 ; Cont: 대조구, F: 법제유황, OTC: oxytetracycline)를 제작하였다. 8주간의 사육 실험 종료 후, 증체율 일간성장률에 있어서 OTC4000 실험구는 Cont, F25, F500, F1000 그리고 F2000 실험구보다 유의하게 높은 값을 나타내었다 (P<0.05). 하지만, F50, F250 그리고 OTC4000 실험구들간에는 유의하게 차이를 보이지 않았고 (P>0.05), Cont, F25, F500, F1000 그리고 F2000 실험구들간에도 유의하게 차이를 보이지 않았다 (P>0.05). 사료효율, 단백질전환효율에 있어서 OTC4000 실험구는 F500, F1000 그리고 F2000 실험구보다 유의하게 높은 값을 나타내었다 (P<0.05). 하지만, Cont, F25, F50, F250 그리고 OTC4000 실험구들간에는 유의하게 차이를 보이지 않았다 (P>0.05). 중성지방에 있어서 F25, F50, F250, F500 그리고 OTC4000 실험구들간에는 유의하게 차이를 보이지 않았다 (P>0.05). 하지만, F1000 실험구가 F25, F50, F250, F500 그리고 OTC4000 실험구들보다 유의하게 높은 값을 나타내었다 (P<0.05). 공격실험으로 Edwardsiella tarda 를 복강 주사한 후 누적 생존율을 조사해본 결과, 6 일째에 F50 실험구가 F2000 실험구보다 유의하게 높은 값을 나타내었다 (P<0.05). 하지만, Cont, F25, F50, F250, F500, F1000 그리고 OTC4000 실험구들간에는 유의하게 차이를 보이지 않았다 (P>0.05). 따라서, 치어기 넙치에 있어 50 ppm의 법제유황의 첨가가 항생제(OTC)를 대체할 수 있을 것으로 판단되었다.

An 8-week feeding trial was conducted to evaluate the optimum dietary processed sulfur (Immuno-F) level to replace antibiotic (OTC) on growth performance, hematology, and disease resistance in juvenile olive flounder. Each of 20 fish averaging 12.6 ± 0.17 g (mean±SD) were randomly allocated into 8 groups of three tanks, and fed one of the eight isonitrogenous and isocaloric (crude protein 46.7%, 160 kJ g-1) experimental diets formulated by supplementing Immuno-F at 0 ppm (Cont), 25 ppm (F25), 50 ppm (F50), 250 ppm (F250), 500 ppm (F500), 1000 ppm (F1000) and 2000 ppm (F2000), or oxytetracycline 4000 ppm (OTC4000). Weight gain and specific growth rate of fish fed OTC4000 diet were significantly higher than those of fish fed Cont, F25, F500, F1000 and F2000 diets (P<0.05). However, there were no significant differences among fish fed F50, F250 and OTC4000 diets (P>0.05), and among fish fed Cont, F25, F500, F1000 and F2000 diets (P>0.05). Feed efficiency and protein efficiency ratio of fish fed OTC4000 diet were significantly higher than those of fish fed F500, F1000 and F2000 diets (P<0.05). However, there were no significant differences among fish fed Cont, F25, F50, F250 and OTC4000 diets (P>0.05). There were no significant differences in serum triglyceride levels of fish fed F25, F50, F250, F500 and OTC4000 diets (P>0.05). However, serum triglyceride levels of fish fed F1000 diet were significantly higher than those of fish fed F25, F50, F250, F500 and OTC4000 diets (P<0.05). For challenge test with Edwardsiella tarda at the 6th day, cumulative survival rates of fish fed F50 diet were significantly higher than those of fish fed F2000 diet (P<0.05). However, there were no significant differences among fish fed Cont, F25, F50, F250, F500, F1000 and OTC4000 diets (P<0.05). Therefore, results may indicate that dietary processed sulfur level of 50 ppm could replace the antibiotic (OTC) in juvenile olive flounder.