Dae-Han Oh

Effects of dietary supplementation of citrus by-products fermented with a probiotic microbe on growth performance, innate immunity and disease resistance against Edwardsiella tarda in juvenile olive flounder, Paralichthys olivaceus (Temminck & Schlegel).

Two consecutive studies were conducted to evaluate the dietary supplementation of citrus by-products (CB) fermented with probiotic bacteria on growth performance, feed utilization, innate immune responses and disease resistance of juvenile olive flounder. In Experiment I, five diets were formulated to contain 0% (control) or 3% four different CB fermented with Bacillus subtilis (BS), Enterococcus faecium (EF), Lactobacillus rhamnosus (LR) and L. plantarum (LP) (designated as CON, CBF-BS, CBF-EF, CBF-LR and CBF-LP, respectively). During 10 weeks of a feeding trial, growth performance and feed efficiency were not significantly different among all the fish groups. However, fish fed CBF containing diets had significantly higher survivals than the CON group. Disease resistance of fish against Edwardsiella tarda was increased by the fermentation of CB. In Experiment II, we chose the BS as a promising probiotic and formulated five diets to contain 0%, 2%, 4%, 6% and 8% CBF-BS. Growth performance was not significantly affected by the CBF-BS supplementation during 6 weeks of a feeding trial. Innate immunity of fish was significantly enhanced by CBF-BS supplementation. Myeloperoxidase and lysozyme activities were increased in a dose-dependent manner by dietary CBF-BS inclusions. In a consecutive challenge test against E. tarda, an increased disease resistance was found by CBF-BS supplementation. These studies indicate that the fermentation process of CB with probiotic has beneficial effects on innate immunity and thereby increases disease resistance of olive flounder against E. tarda. Bacillus subtilis can be used as a promising probiotic microbe for by-product fermentation in fish feeds.

Effect of Food Particle Size, Stocking Density and Feeding Frequency on the Growth Performance of Juvenile Korean Rockfish Sebastes schlegelii

We performed four sets of feeding trials to establish optimum feed size (Exp-I), stocking density (Exp-II) and feeding frequency (Exp-III and IV) for Korean rockfish. In Exp-I, three different particle sizes of a commercial diet (small, 2.0-2.1 mm; medium, 2.4-3.2 mm; and large, 4.0-5.3 mm) were fed to four replicate groups of fish (), each of which was fed to apparent satiation for six weeks. In Exp-II, fish () were reared at four stocking densities (1.5, 3.0, 4.5 and 6.0 ) and fed a commercial diet to apparent satiation for four weeks. In Exp-III, fish () were fed a commercial diet once, twice, thrice, or a day at a feeding ratio of 3.25% of body mass. Another group of fish was fed the same commercial diet a day to apparent satiation; this treatment was designated FS (five times satiation/day). In Exp-IV, fish () were fed a commercial diet once, twice, thrice or a day to apparent satiation. Another group of fish was fed to apparent satiation once every 48 hours. In Exp-I, fish fed the large particle (4.0-5.3 mm) diet had a significantly higher feed conversion ratio and lower protein efficiency ratio than fish fed the small particle diet. In Exp-II, groups of fish reared at densities of 4.5 and 6.0 had significantly higher feed intake and growth performance than fish reared at 1.5 and 3.0 . In Exp-III, fish fed to apparent satiation had significantly higher growth performances than fish fed once or a day. A significantly higher feed conversion ratio and a lower protein efficiency ratio were obtained in the FS group. In Exp-IV, growth performance and feed utilization efficiency were not significantly affected by experimental variation in feeding frequency. Fish fed to apparent satiation once every 48 hours had better feed utilization than those in other treatments and growth performances of those were comparable. Therefore, the optimum feed particle size, stocking density and feeding frequency for Korean rockfish under conditions we used were 2.0-3.2 mm, 4.5-6.0 , and once a day or once every 48 hour, respectively.

Effects of Dietary Supplementation with Bacillus sp. on Growth Performance, Feed Utilization, Innate Immunity and Disease Resistance against Streptococcus iniae in Olive Flounder Paralichthys olivaceus

We investigated the effect of dietary supplementation with probiotics on growth performance, feed utilization, innate immunity and disease resistance against Streptococcus iniae in juvenile olive flounder Paralichthys olivaceus. Four experimental diets were made by supplementation with three Bacillus sp. probiotics (B. subtilis, B. pumilus and B. licheniformis) into a basal diet (control) at 0.5% each. Three-hundred fish (average BW, 20 g) were randomly distributed (25 per tank) into twelve 150 L capacity polyvinyl circular tanks with three replicates per dietary treatment. Triplicate groups of fish were fed the experimental diets to apparent satiation (twice per day, 09:00 and 17:00 h) for nine weeks. After the feeding trial, a challenge test was directly conducted against S. iniae. The results indicated that dietary supplementation with the probiotic, Bacillus sp, seemed to improve growth performance of olive flounder. Hematological parameters and innate immunity as determined by nitroblue tetrazolium, myeloperoxidase or superoxide dismutase activities were not significantly affected by the probiotic supplementation. The result from the challenge test suggested that dietary supplementation with probiotics Bacillus sp. can improve the disease resistance of olive flounder against S. iniae.

Effect of Dietary Supplementation with Alga (Hizikia fusiformis and Ecklonia cava) on the Non-specific Immune Responses of Parrot Fish Oplegnathus fasciatus

Two feeding trials were conducted to determine the effects of dietary supplementation with Hizikia fusiformis or Ecklonia cava on the non-specifi c immune responses of parrot fi sh Oplegnathus fasciatus. Fish were fed experimental diets to which H. fusiformis or E. cava powder were added to fi nal concentrations of 0, 2, 4 and 6%, respectively. After feeding for two weeks, phagocytic activity was signifi cantly higher in fi sh fed diets containing H. fusiformis, but not E. cava, than in fi sh fed the basal diet. Lysozyme activity was signifi cantly increased in the fi sh fed diets containing 6% H. fusiformis and E. cava. Myeloperoxidase activity was also signifi cantly higher in fi sh fed diets containing 2 and 4% H. fusiformis, as compared to the basal diet, but not in those fi sh fed E. cava. These two studies indicate that dietary supplementation with H. fusiformis or E. cava could enhance the innate immune responses of parrot fi sh during their growth stage.

Optimum Feeding Rate for Growing Olive Flounder (317 g) Paralichthys olivaceus Fed Practical Extruded Pellets at Optimum Water Temperature (21-24℃)

We investigated the effects of feeding rate on the growth performance, blood components, and histology of grow-ing olive flounder Paralichthys olivaceus. Optimum feeding rate (initial fish mean weight : 316.7±6.18 g) was de-termined under the optimum water temperature. Two replicated groups of fish were fed a commercial diet at rates of 0%, 0.4%, 0.6%, and 0.8% of body weight (BW) per day, and to satiation. Feeding trial was conducted using a flow-through system with 10 1.2-metric ton aquaria receiving filtered seawater at 21-24°C for 3 weeks. Weight gain (WG) and specific growth rate (SGR) were significantly higher in fish fed to satiation (1.0% BW/day) than in those in other treatments. These parameters were negative and significantly lower in the starved fish than in fish fed the experimental diet at all feeding rates. There were no significant differences in WG and SGR among fish fed at 0.4%, 0.6%, and 0.8% BW/day. Hematocrit and hemoglobin in fish fed to satiation were significantly lower than those in other treatments. Histological changes of fish fed at 0.6% BW/day indicated that this group was in the best condition; differences were not found in tissues of fish fed at 0%, 0.6% and 1.0% BW/day. Broken-line regression analysis of weight gain showed that the optimum feeding rate of olive flounder weighing 317 g was 0.99% BW per day at the optimum water temperature.Key words: Olive flounder, Feeding rate, Optimum water temperature, Histology, Hepatopancreas

Evaluation of Acid-concentrated Soybean Meal as a Fishmeal Replacement and its Digestibility in Diets for Juvenile Olive Flounder Paralichthys olivaceus

This study was conducted to investigate the effects of fishmeal replacement with acid-concentrated soybean meal (ACSBM) on growth performance, blood biochemistry, and ingredient digestibility in juvenile olive flounder Para-lichthys olivaceus. Six experimental diets were formulated to replace fishmeal protein with ACSBM at 0%, 20%, 30%, 40%, 50%, and 60% (designated ACSBM0, ACSBM20, ACSBM30, ACSBM40, ACSBM50, and ACSBM60, respectively). Triplicate groups of fish (initial fish mean weight: 14.3±0.03 g) were fed the experimental diets to apparent satiation (twice daily at 08:00 and 18:00 h). After a 12-week feeding trial, a total of 180 healthy fish were randomly distributed into three Guelph system tanks at a density of 60 fish/tank (initial fish mean weight : 50.6±2.4 g) to test the apparent digestibility coefficients of the ingredients (ACSBM, fishmeal, and soybean meal). Although negative effects were observed with ACSBM40, ACSBM50 and ACSBM60 after 12 weeks of feeding, up to 20% of the fishmeal protein could be successfully replaced with ACSBM without significant growth depression. Hemoglobin and hematocrit values of fish fed the ACSBM50 and ACSBM60 diets were significantly lower than those of fish fed the ACSBM0 diet. Glucose values of fish fed the ACSBM60 diet were significantly higher than those of fish fed the ACSBM0 and ACSBM20 diets. Digestibility of protein in ACSBM and soybean meal was 85.9% and 82.5%, respec -tively. Results indicated that at least 20% of fishmeal protein can be replaced by ACSBM in diets of juvenile olive flounder without supplementation of limiting amino acids. Key words: Olive flounder, Fish meal, Acid-concentrated soybean meal, Digestibility, Replacement

Effects of Dietary Supplementation with Nucleotide on Growth Performance, Feed Utilization, and Non-Specific Immune Responses of Nile Tilapia Oreochromis niloticus

The present study examined the effects of dietary supplementation with nucleotide (inosine monophosphate product, IMP) on the growth performance, feed utilization, and non-specific immune responses of juvenile tilapia Oreochromis niloticus. Triplicate groups of tilapia (initial body weight, g) were fed experimental diets containing 0%, 0.05%, 0.1%, and 0.2% IMP. Fish were fed six times a day until apparent satiation for 13 weeks. At the end of the feeding trial, final body weight and food utilization of fish fed 0.1% IMP were significantly higher than those of fish fed the control diet. Results of hematological parameters were not affected by dietary IMP. However, blood protein level was significantly higher in the 0.05% treatment, as compared to that of the control and 0.2% IMP diets. Myeloperoxidase activity was higher in fish fed 0.1% IMP than in fish fed the control and 0.2% IMP diets. These results suggest that dietary supplementation with IMP can enhance the growth performance, feed utilization, and innate immune response of juvenile tilapia. The optimal IMP supplementation level appears to be 0.1% in practical feed formulations for tilapia.

Optimal Feeding Rates of Subadult Korean Rockfish Sebastes schlegeli Fed a Commercial Diet at Different Water Temperatures

조피볼락(Sebastes schlegeli)은 국내에서 넙치 다음 두 번째 로 많이 양식 생산되는 육식성 해산어종으로 국내 어류양식 총 생산량의 약 33%인 23,033톤을 차지한다(Statistics Korea, 2013). 조피볼락을 포함한 대부분의 어류양식에서 배합사료의 효율적이며 체계적인 공급방법은 매우 중요한 요소로 작용한 다(Azzayedi et al., 2000). 어류양식 경영에 있어서 배합사료 의 비용은 총 양식경영비의 50-60%를 차지함으로써 양식경영 의 수익성에 가장 밀접한 영향을 미치는 요인이다(Cho et al., 2006). 이러한 이유로 배합사료의 체계적인 공급방법과 공급량 에 관한 연구들이 지속적으로 이루어지고 있다(Myeong et al., 1997; Lee et al., 2013a; Kim et al., 2010). 최근 국내 양식산업 에서도 배합사료의 체계적인 공급방법과 공급량 및 공급 횟수 에 관한 연구의 필요성이 대두되면서 조피볼락을 대상으로 한 일련의 연구결과들이 보고되고 있다(Oh et al., 2013; Lee et al., 2013a, 2013b). 사료의 과잉 공급은 사료의 유실 뿐 만 아니라, 어체 내 사료의 비효율적인 이용으로 인한 사료 허실을 초래하 여 경제적인 손실과 수질 오염원을 증가시키게 된다(Kim et al., 2012). 또한, 배합사료를 만복공급 형태로 과잉공급 하면 사료 계수가 올라가고 복수증, 탈장 등과 같은 질병발생의 원인이 되 기도 한다(Biswas et al., 2006). 이와 반대로 사료를 부족하게 공급하면 어류의 최대 성장에 필요한 영양소 요구량을 충족시 키지 못하여 어류의 성장 저하를 초래하게 된다(Tsevis et al., 1992; Azzaydi et al., 2000). 수온은 어류의 성장과 발육을 결정짓는 중요한 요인으로 어류 의 섭식욕구에 직접적인 영향을 준다(Choi et al., 2002). 수온 이 낮아지면 어류 체내의 소화효소 활성 및 대사율이 감소하게 저수온, 적수온, 고수온에서 미성어기 조피볼락(Sebastes schlegeli)의 배합사료 적정 공급률 김민기·이초롱·김유정·오대한·이봉주·김성삼·이경준*

Effects of Dietary Protein and Lipid Levels on the Growth Performance, Feed Utilization and Innate Immunity of Juvenile Red Seabream Pagrus major

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Fish meal replacement by soybean meal in diets for Tiger puffer, Takifugu rubripes

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