First Evidence for Hybrid Breakdown in the Backcross of Olive Flounder,Paralichthys olivaceus,and Summer Flounder,Paralichthys dentatus

Hybrid and parental backcross experiments were performed using olive flounder, Paralichthys olivaceus, summer flounder, Paralichthys dentatus, and their female F₁ hybrids to examine hybrid fitness in the backcross. Fertilization rate, hatching rate, and combined fitness measure (CFM, product of fertilization rate and hatching rate) were detected and the results showed that the CFM of hybrid and backcross generations was reduced significantly compared to pure olive flounder crosses. Genomic inheritance from parents to backcross progeny was also detected by amplified fragment length polymorphism (AFLP). Almost all AFLP bands observed in parents were presented in backcross progeny (backcross1, 218/227; backcross2, 265/282), although 9 and 17 parental bands were missing in backcross1 and backcross2, respectively. Novel bands (absent in parents) also occurred in progeny at the frequencies of 5.63% (13/231) in backcross1 and 3.28% (9/274) in backcross2. Additionally, 27.40 and 31.18% of AFLP markers deviated from expected Mendelian ratio in backcross1 and backcross2, respectively. The present study suggests that genetic incompatibilities may exist between olive flounder and summer flounder. Furthermore, possible implications of segregation distortion for reduced hybrid fitness in backcross generations are discussed.     

Compensatory Growth of Olive Flounder,Paralichthys olivaceus,Fed the Extruded Pellet with Different Feeding Regimes

This study was performed to determine compensatory growth of juvenile olive flounder fed the extruded pellet (EP) with different feeding regimes. Seven treatments with triplicates of different feeding regimes were prepared; α fish was daily fed for 6 d a week throughout 8 wk (8WF); α fish was starved for 1 wk and then fed for 3 wk twice [(1WS + 3WF) × 2]; β fish was starved for 2 wk and then fed for 6 wk (2WS + 6WF); χ fish was starved for 5 d and then fed for 9 d four times [(5DS + 9DF) × 4]; δ fish was starved for 10 d and then fed for 18 d twice [(10DS + 18DF) × 2]; δ fish was starved for 2 d, fed for 5 d, starved for 3 d, and then fed for 4 d four times [(2DS + 5DF + 3DS + 4DF) × 4]; and φ fish was starved for 4 d, fed for 10 d, starved for 6 d, and then fed for 8 d twice [(4DS + 10DF + 6DS + 8DF) × 2], respectively. Total feeding day was all same, 36 d except for control group (48 d). Weight gain of flounder in the 8WF treatment was higher than that of fish in other treatments. And weight gain of flounder in the 2WS + 6WF treatment was higher than that of fish in the (5DS + 9DF) × 4 and (4DS + 10DF + 6DS + 8DF) × 2 treatments. Feed consumption of flounder in the 8WF treatment was higher than that of fish experienced feed deprivation. Feed efficiency ratio (FER), protein efficiency ratio (PER), and protein retention (PR) were not significantly different among treatments. Chemical composition of the whole body of fish with and without liver, except for moisture content of liver, was not different among treatments. T₃ level of fish in the 8WF and 2WS + 6WF treatments was higher than that of fish in the (5DS + 9DF) × 4 treatment. It can be concluded that juvenile olive flounder achieved better compensatory growth at 6‐wk refeeding after 2‐wk feed deprivation compared with that of fish with different feeding regimes. And T₃ level of fish seemed to partially play an important role in achieving compensatory growth.     

Onion Powder in the Diet of the Olive Flounder,Paralichthys olivaceus: Effects on the Growth,Body Composition,and Lysozyme Activity

This study tested the onion powder (OP) supplementation in the diet of the olive flounder on the growth, body composition, and lysozyme activity. Thirty‐five fish averaging 5.1 g were randomly stocked into 18 individual 180‐L flow‐through tanks. A commercially available OP was used as a dietary additive. Six experimental diets were prepared to contain OP at the concentrations of 0, 0.5, 1, 2, 3, and 5% for diets OP‐0, OP‐0.5, OP‐1, OP‐2, OP‐3, and OP‐5, respectively. After the 8‐wk feeding trial, 20 fish from each tank were infected with Edwardsiella tarda and mortality was monitored for the following 96 h. No distinctive improvement in survival, weight gain, or feed efficiency of fish was observed at the end of the 8‐wk feeding trial. Lysozyme activity in fish fed the OP‐0.5 diet was higher than that of fish fed the OP‐0, OP‐1, OP‐2, OP‐3, and OP‐5 diets. The cumulative mortality of fish fed the OP‐0.5, OP‐1, OP‐2, OP‐3, and OP‐5 diets was lower than that of fish fed the OP‐0 diet at 72 h after E. tarda infection. Dietary inclusion of 0.5% OP was effective at improving lysozyme activity of fish, and OP seemed to be an effective immunostimulant to lower mortality upon E. tarda infection.     

Long‐term Effects of Passive Integrated Transponder Tagging on the Growth of Olive Flounder,Paralichthys olivaceus

The effects of passive integrated transponder (PIT) tagging on the growth and survival of olive flounder, Paralichthys olivaceus (initial average mass ± SD: 502 g ± 14.3), were examined for 8 mo. Tag readability in relation to implant position (eyed‐side muscle, blind‐side muscle, and peritoneal cavity) was also documented. The overall weight gain of fish tagged in the eyed‐side muscle (444 g) was significantly less than control and tagged fish in the blind‐side muscle and peritoneal cavity, which showed 470–488 g of weight gain (KW, P < 0.001, N= 78, df = 3). Specific growth rates (%/d) did not differ significantly (P > 0.05) among control, blind‐side muscle, and peritoneal cavity groups. No significant (P > 0.05) difference in survival rate was found between treatment and control. The readability of PIT tags in all implanted positions was 100%. The average time spent tagging at each position was less than 30 sec. These results show that PIT tagging of olive flounder weighing approximately 500 g in the blind‐side muscle and peritoneal cavity is feasible and reliable with fewer negative effects on growth than observed on the eyed‐side muscle site trial.     

Effects of Putative Growth or Health‐Enhancing Dietary Additives on Juvenile Olive Flounder,Paralichthys olivaceus,Performance

The effect on growth and body composition of various dietary additives with putative growth or health‐enhancing properties were determined in juvenile olive flounder (25 g initial weight). Nine experimental diets were prepared to contain one of the following additives: control (Con) with no additive, Opuntia ficus‐indica ver. saboten (OF), propolis (PP), lactic acid bacteria (LA), γ‐poly‐glutamic acid (PG), onion extract (OE), organic sulfur (OS), Biostone® (BS), and fig extract (FE). Fishmeal, dehulled soybean meal, and corn gluten were used as the protein source of the experimental diets. Wheat flour and soybean oil were used as the carbohydrate and lipid sources, respectively. Dietary additives were included in each experimental diet at 1% at the expense of wheat flour except for the FE (aqueous), which was substituted at 1% of the amount of water added to the diet. Fish were hand‐fed to satiation twice a day for 6 d/wk for 6 wk. Weight gain of fish fed the OE diet was higher than that of fish fed with the PP diet. Chemical composition of fish was not different among the experimental diets. OE was the most effective dietary additive to improve performance of olive flounder among additives used in this study.     

Effect of Daily Feeding Ratio on Growth and Body Composition of Subadult Olive Flounder, Paralichthys olivaceus, Fed an Extruded Diet during the Summer Season

A 10‐wk feeding trial to determine the effect of daily feeding ratio on growth and body composition of subadult olive flounder fed the extruded pellet (EP) was performed during the summer season. Thirteen flounder (an initial body weight of 319 g) per tank were distributed into fifteen 500‐L flow‐through tanks. Five treatments of feeding ratio in 5% decrement were prepared in triplicate: 100 (satiation), 95, 90, 85, and 80% of satiation. Fish in the control group (100% of satiation) were hand‐fed to apparent satiation twice a day. Then, feed allowance in the rest of the four groups was determined based on average feed consumption of fish in the control group. Weight gain of fish fed to 100% of satiation was significantly (P < 0.05) higher than that of fish fed to 85 and 80% of satiation but not significantly (P > 0.05) different from that of fish fed to 95 and 90% of satiation. Serum total protein, glucose, and glutamic pyruvic transaminase were not significantly (P > 0.05) affected by feeding ratio but triglyceride and glutamic oxaloacetic transaminase were. In considering these results, it can be concluded that optimum daily feeding ratio for growth of subadult olive flounder seemed to be 90% of satiation when fish were fed the EP twice a day during the summer season.     

Optimum Dietary Protein Levels and Protein to Energy Ratios in Olive Flounder Paralichthys olivaceus

The olive flounder Paralichthys olivaceus is one of the most commercially important fish species in Korea. In order to formulate better diets for cultured olive flounder we evaluated the optimum dietary protein requirements for larval, fry and juvenile olive flounder, and the optimum dietary protein to energy ratio for juvenile olive flounder. Results of four separate experiments suggested that the optimum dietary protein requirements were 60% in larvae (0.3 g), 46.4–51.2% in 4.1-g juvenile, and 40–44% in 13.3 g growing olive flounder. The optimum dietary protein to energy ratio based on weight gain, feed efficiency, specific growth rate, and protein retention efficiency was 27–28 mg protein/kJ 2 energy (35 and 45% CP for diets containing 12.5 and 16.7 kJ energylg diet, respectively).     

Evaluation of Toxicity of Dietary Chelated Copper in Juvenile Olive Flounder,Paralichthys olivaceus,Based on Growth and Tissue Copper Concentration

The present study was conducted to determine the safe and toxic levels of dietary copper in juvenile olive flounder, Paralichthys olivaceus, fed Mintrex^® copper, a chelated dietary copper source. Fish averaging 3.8 ± 0.13 g (mean ± SD) were fed 1 of 10 diets (n = 3) containing 7 (Cu₀), 10.4 (CuM₅), 15.8 (CuM₁₀), 24.9 (CuM₂₀), 43.4 (CuM₄₀), 82.1 (CuM₈₀), 158 (CuM₁₆₀), 308 (CuM₃₂₀), 658 (CuM₆₄₀), and 1267 (CuM₁₂₈₀) mg Cu/kg diet. At the end of 12 wk of feeding trial, weight gain (WG), specific growth rate, and protein efficiency ratio of fish fed CuM₅ and CuM₁₀ diets were significantly higher than those fed CuM₈₀, CuM₁₆₀, CuM₃₂₀, CuM₆₄₀, and CuM₁₂₈₀ diets (P < 0.05). Survival of fish fed Cu₀, CuM₅, CuM₁₀, CuM₂₀, and CuM₄₀ diets was significantly higher than those of fish fed CuM₃₂₀, CuM₆₄₀, and CuM₁₂₈₀ diets. Whole‐body lipid content of fish decreased while whole‐body ash increased with dietary copper levels. Whole‐body and tissue copper concentrations increased with dietary copper levels. Although ANOVA test suggested that the toxic level of dietary Cu in juvenile olive flounder, P. olivaceus, could be 320 mg/kg diet, broken‐line analysis of WG indicated a level of 286 mg/kg diet when Mintrex^®Cu is used as the dietary copper source.     

Optimum Dietary Level of Chlorella Powder as a Feed Additive for Growth Performance of Juvenile Olive Flounder,Paralichthys olivaceus

ABSTRACT

The present study was conducted toestimate the optimum dietary supplementation level of Chlorella powder as a feed additive to optimize growth of juvenile olive flounder, Paralichthys olivaceus. Four experimental diets supplemented with Chlorella powder (CHP) at 0, 1, 2 and 4% (CHP₀, CHP₁, CHP₂, and CHP₄, respectively) of diet as a dry-matter (DM) basis were prepared. Three replicate groups of fish averaging 1.1±0.02 g were fed one of the four experimental diets for 12 weeks. After the feeding trial, fish fed the CHP₂ diet had a higher (P < 0.05) weight gain (819%) than did fish fed CHP₀ (707%) and CHP₁(712%); however, there was no significant difference between fish fed CHP₂ (8197%) and CHP₄ (7559%) as among fish fed CHP₀, CHP₁, and CHP₄ (P > 0.05). Fish fed CHP₂ had a higher (P < 0.05) feed efficiency (134%) than did fish fed CHP₀ (123%); however, there was no significant difference (P > 0.05) among fish fed CHP₀ (123%), CHP₁ (125%), and CHP₄ (125%) as among fish fed CHP1 (125%), CHP₂ (134%), and CHP₄ (125%). Fish fed CHP₂ and CHP₄ had a lower (P < 0.05) serum glucose level (average 32.9 mg/dL) than did fish fed CHP₀ and CHP1 (average 34.8 mg/dL). Fish fed CHP1 and CHP₂ had a lower (P < 0.05) serum glutamic oxaloacetic transaminase (GOT) level than did fish fed CHP0 and CHP₄. Glutamic pyruvic transaminase (GPT) levels significantly (P < 0.05) deceased as dietary CHP increased. Fish fed CHP₂ and CHP₄ had a less (P < 0.05) whole-body fat than did fish fed CHP₀. These results indicate that the optimum dietary supplementation level of Chlorella powder as a feed additive in juvenile olive flounder could be approximately 2% of diet.     

Pharmacokinetics of Eugenol in Japanese Flounder,Paralichthys olivaceus

Eugenol, which has been used as an anesthetic for fish, was administered to Japanese flounder, Paralichthys olivaceus (127 ± 50.8 g), by bath treatment at concentrations of 0.025, 0.125, and 0.25 mL/L seawater for 10 min and intramuscular injection at 40 μL/fish to investigate the pharmacokinetic characteristics of eugenol in the plasma of Japanese flounder. In the bath treatment test, plasma eugenol concentration increased with increasing eugenol concentration up to 0.125 mL/L and reached steady state within 5 min. After a 10‐min bath treatment in 0.25 mL/L eugenol, plasma eugenol concentration was about 58.4 µg/mL. After transfer into running seawater, plasma eugenol concentration decreased biphasically with half‐lives of 0.0296 h (α‐phase) and 0.289 h (β‐phase). The AUC_0000→0800 was about 16.5 µg h/mL. In administration by intramuscular injection, plasma eugenol concentration increased rapidly after administration and decreased biphasically with half‐lives of 0.0329 h (α‐phase) and 8.08 h (β‐phase). The AUC_0000→0800 was about 52.5 µg h/mL. In both methods of administration, Japanese flounder with average weight of 127 g were effectively anesthetized when plasma eugenol concentrations were between 2.19 and 4.88 µg/mL.     

舟山海域褐牙鲆全人工繁育技术研究

2010年3月至6月,在浙江省海洋水产研究所西闪试验场进行了舟山褐牙鲆全人工繁育技术研究。在水温16.0～23.0℃,盐度26～27,溶解氧5.0～6.0mg/L的条件下,历经60d的培育,累计育成平均全长3.6cm以上的牙鲆鱼苗80×104万尾,受精率87.9%,孵化率90.9%,全长3cm～5cm的鱼苗培育成活率32%。     

Effects of Dietary Protein and Energy Levels on Growth and Body Composition of Juvenile Flounder Paralichthys olivaceus

A feeding trial of three protein levels (30, 40 and 50%) and two energy levels (300 and 400 kcal/100-g diet) factorial design with three replications was carried out to investigate the proper dietary protein and energy levels for the growth of juvenile flounder Paralichthys olivaceus . Weight gain of fish tended to improve with increasing dietary protein level. Weight gain of fish fed either the 40% or 50% protein diet with 300 kcal/100-g diet was significantly higher ( P < 0.05) than with 400 kcal/100-g diet. The best weight gain was obtained from fish fed the 50% protein diet with 300 kcal/100-g diet. Feed efficiency tended to improve with increasing dietary protein level. However, dietary energy level had no significant effect on feed efficiency of fish fed the 30% or 50% protein diet, but that of fish fed the 40% protein diet with 300 kcal/100-g diet was significantly higher than with 400 kcal/100-g diet. Protein retention tended to increase as dietary protein level increased and energy level decreased. Lipid content of fish fed the diet containing 400 kcal/100-g diet was significantly higher than that of fish fed the diet containing 300 kcal/100-g diet at all protein levels. Fatty acid compositions such as linoleic acid, EPA (20:5n-3) and DHA (22:6n-3) offish were directly affected by dietary lipid (squid liver oil and/or soybean oil) used for energy source. Based on the above results, it can be concluded that the proper dietary protein and energy levels for the growth of juvenile flounder are 50% and 300 kcal/100-g diet, respectively.     

Compensatory Growth of Juvenile Olive Flounder, Paralichthys olivaceus L., and Changes in Proximate Composition and Body Condition Indexes during Fasting and after Refeeding in Summer Season

Compensatory growth of juvenile olive flounder, Paralichthys olivaceus L., and changes in proximate composition and body condition indexes of fish during fasting and after refeeding were investigated during the summer season. Groups of 25 fish each (initial body weight of 16 g) were randomly distributed into fifteen 180‐L flow‐through tanks. Fish were fed the experimental diet containing crude protein 46.9% and crude lipid 8.0% with estimated energy level of 14.6 kJ/g diet for 6 d/wk. Five treatments in triplicate were prepared for this study: C, S1, S2, S3, and S4. Fish in the control group (C) were hand‐fed to apparent satiation twice daily. Fish in treatments S1, S2, S3, and S4 experienced 1, 2, 3, and 4 wk of starvation and were then hand‐fed to apparent satiation twice daily during the remaining 7, 6, 5, and 4 wk of the experiment, respectively. A group of starved fish in the similar size was stocked and fasted throughout the 8‐wk feeding trial for chemical and blood analysis. The feeding trial lasted for 8 wk. Weight of fish linearly decreased with week of starvation (P < 0.0001). Linear relationship between condition factor (CF) and hepatosomatic index (HSI) against week of starvation was observed in the starved group of fish. Survival was not significantly (P > 0.05) affected by feeding strategy. However, weight gain and specific growth rate (SGR) of olive flounder in C, S1, and S2 were significantly (P < 0.05) higher than those of fish in S3 and S4. The poorest weight gain and specific growth rate (SGR) were obtained in fish of S4. Feed consumption of olive flounder in C, S1, and S2 was significantly (P < 0.05) higher than that of fish in S3 and S4. Feed efficiency, protein efficiency ratio, and protein retention of olive flounder in C and S1 were not significantly (P > 0.05) different from those of fish in S2 but significantly (P < 0.05) higher than those of fish in S3 and S4. Hematocrit, CF, and HSI of olive flounder were not significantly (P > 0.05) affected by feeding strategy. Chemical composition of fish was not significantly (P > 0.05) affected by feeding strategy. In considering these results, it can be concluded that juvenile olive flounder have the ability to fully compensate for 2‐wk feed deprivation during the summer season. Besides, feed efficiency in fish fed for 7 and 6 wk after 1‐ and 2‐wk feed deprivation was comparable to that in fish fed for 8 wk.     

Effects of Dietary Inclusion of Chlorella vulgaris on Growth,Blood Biochemical Parameters,and Antioxidant Enzyme Activity in Olive Flounder,Paralichthys olivaceus

This study was carried out to investigate the effects of dietary inclusion of defatted Chlorella on growth performance, body composition, blood biochemistry, and antioxidant enzyme activity in olive flounder. Four isonitrogenous (51% crude protein) diets were formulated to contain 0 (control), 5, 10, or 15% Chlorella meal (CM) (designated as Con, CM5, CM10, and CM15, respectively) and fed to triplicate groups of fish (104.4 g) to apparent satiation twice daily for 8 wk. At the end of the feeding trial, significant enhancement (P < 0.05) in growth performance was obtained at over 10% CM compared to fish fed the control diet. No significant changes in dorsal muscle and liver proximate composition were found following CM administration. The groups fed CM‐containing diets revealed significantly lower plasma cholesterol concentration than those fed the control diet. Dietary CM affected antioxidant enzyme activity; significantly higher plasma catalase activity was found in fish fed ≥10% CM and total antioxidant capacity increased in CM5 and CM10 groups compared to the control. However, plasma glutathione peroxidase and superoxide dismutase activities were not significantly influenced by dietary CM. Also, significant enhancement in 1,1‐diphenyl‐2‐picryl‐hydrazyl radical scavenging activity was found in dorsal muscle of fish fed CM15 diet compared to the control. The findings in this study showed that dietary inclusion of 10–15% CM can enhance growth performance and affect antioxidant enzyme activity and lipid metabolism in olive flounder.     

牙鲆仔鱼核酸与生长关系的研究

随机采取不同日龄健康的牙鲆仔鱼,用电子目镜和天平测定其全长（L）、体质量（m）,运用整体匀浆法测定鱼体中核酸和总蛋白浓度、RNA／DNA （a）比值和总蛋白／DNA比值（b）,研究了牙鲆仔鱼的生长,DNA、RNA和总蛋白的变化规律,探讨了核酸、总蛋白和生长的关系。试验结果表明,牙鲆仔鱼体质量、全长与RNA／DNA比值均呈线性负相关,关系式分别为 m＝-19．85 a＋82．79（r2＝0．89, P＜0．01）,L＝-7．41 a＋33．53（r2＝0．85,P＜0．05）。上述关系式说明,牙鲆仔鱼时期的生长以细胞增殖为主,大量消耗前期合成的蛋白质。牙鲆仔鱼体质量、全长与总蛋白／DNA 比值也呈线性负相关,关系式分别为 m＝-0．61 b ＋34．54（r2＝0．93, P ＜0．01）,L＝-0．22 b ＋15．33（r2＝0．86, P ＜0．01）。随着牙鲆仔鱼养殖日龄的增加,总蛋白／DNA比值下降的幅度大于RNA／DNA比值。核酸指标能从细胞水平上分析仔鱼的生长。     

Effect of Dietary Inclusion of Blue Mussel Extract on Growth and Body Composition of Japanese Flounder Paralichthys olivaceus

Dietary inclusion of a water-soluble fraction of blue mussel Mytilus galloprovincialis was examined as a feeding stimulant for juvenile Japanese flounder Paralichthys olivaceus . The control diet mainly consisted of fish meal, potato starch, and pollack liver oil. Five, 10, and 20% (weight/weight) of the control diet was exchanged with aqueous extracts of blue mussel meat in experimental groups. Fish of about 10 g in initial body weight were fed each diet to satiation, twice daily, 6 d per wk for 6 wk at 20 C. The final body weight, weight gain, and feed efficiency of fish fed the diets containing blue mussel extracts were significantly higher than those of fish fed the control diet. However, these parameters were not different among experimental groups containing blue mussel extract independent of the inclusion level of extract. A similar trend was shown in protein efficiency ratio as fish fed the control diet had a significantly lower protein efficiency ratio than the other dietary groups. Compared to the control diet, higher plasma protein and lower triglyceride were found in fish fed the diets with the extract, while other blood constituents were relatively similar for the dietary groups tested. On the other hand, whole-body crude lipid content and lipid retention of fish fed the diets with the extract were generally significantly higher than those of fish fed the control diet. Whole body crude protein was identical regardless of the dietary composition; however, protein retention of fish showed a similar trend to lipid retention.     

Effects of Dietary β-1,3 Glucan and Feed Stimulants in Juvenile Olive Flounder, Paralichthys olivaceus

Abstract.— The present study was conducted to investigate the effects of dietary supplementation of β‐1,3 glucan and a laboratory developed feed stimulant, BAISM, as feed additives for juvenile olive flounder, Paralichthys olivaceus. Eight experimental diets were formulated to be isonitrogenous and isocaloric and to contain 50.0% crude protein and 16.4 kJ of available energy/g with or without dietary β‐1,3 glucan and BAISM supplementation. β‐1,3 glucan (G) and BAISM (B) were provided at 0% in the control diet (G₀B₀) and at 0.05% G + 0.45% B (G_0.05B_0.45), 0.05% G + 0.95% B (G_0.05B_0.95), 0.1% G + 0.90% B (G_0.1B_0.9), 0.10% G + 1.90% B (G_0.1B_1.9), 0.15% G + 1.35% B (G_0.15B_1.35), 0.15% G + 2.85% B (G_0.15B_2.85), and 0.30% G + 2.70% B (G_0.3B_2.7) in experimental diets. After the feeding trial, fish fed G_0.1B_0.9, G_0.1B_1.9, and G_0.15B_1.35 diets had higher percent weight gain (WG), feed efficiency ratio (FER), specific growth rate (SGR), protein efficiency ratio (PER), and condition factor (CF) than those fed G₀B₀, G_0.05B_0.45, G_0.05B_0.95, G_0.15B_2.85, and G_0.3B_2.7 diets (P < 0.05); however, there was no significant differences among fish fed G_0.1B_0.9, G_0.1B_1.9, and G_0.15B_1.35 diets. Fish fed G_0.1B_0.9 and G_0.1B_1.9 diets had higher chemiluminescent responses (CL) than those fed the other diets (P < 0.05). Lysozyme activity of fish fed G_0.1B_0.9 diet was significantly higher than that of fish fed the other diets (P < 0.05). These results indicated that the optimum dietary supplementation level of β‐1,3 glucan and BAISM could be approximately 0.10% β‐1,3 glucan + 0.90% BAISM (G_0.1B_0.9) of diet based on WG, FER, SGR, PER, CF, CL, and lysozyme activity in juvenile olive flounder, P. olivaceus.     

Efficacy of Liriope platyphylla on Hematology and Immune Response in Olive Flounder,Paralichthys olivaceus,Against Flexibacter maritimus Infection

The effect of different solvent‐based (methanol, ethanol, and aqueous) extracts of Liriope platyphylla at 0, 0.1, 1.0, and 2.0 mg doses on hematology and innate immune response in olive flounder, Paralichthys olivaceus, against Flexibacter maritimus is reported. The red blood cells and white blood cells significantly increased with ethanol and aqueous extracts with any dose against F. maritimus while the hematocrit level significantly increased with methanol or ethanol extracts. However, the hemoglobin content significantly increased irrespective of the doses and type of extracts, whereas the mean corpuscular volume, mean corpuscular hemoglobin, and mean corpuscular hemoglobin concentration significantly decreased. The lymphocytes and monocytes significantly increased in all doses and extracts, whereas neutrophils increased in ethanol or aqueous extracts. However, the thrombocytes level neither the doses nor extracts did not significant changes to the control against pathogen. Total protein and globulin levels significantly increased with all the doses of ethanol extract while does not significant change in methanol extract. The phagocytic activity and complement activity were significantly enhanced with any dose of ethanol extract while with aqueous extract it was only at 1.0 and 2.0 mg doses. At all the doses of each extract significantly enhanced the leucocytes activity against F. maritimus. The results confirm that the ethanolic and aqueous extracts of L. platyphylla stimulate the immune response against F. maritimus in P. olivaceus.     

Supplementation of Protein Hydrolysates to a Low‐fishmeal Diet Improves Growth and Health Status of Juvenile Olive Flounder,Paralichthys olivaceus

An 11‐wk feeding trial was conducted to evaluate three different protein hydrolysates as feed ingredients in high‐plant‐protein diets for juvenile olive flounder. Five experimental diets were fed to juvenile olive flounder to examine the effect of three different protein hydrolysates on growth performance, innate immunity, and disease resistance against bacterial infection. A basal fishmeal (FM)‐based diet was regarded as a high‐FM diet (HFM) and a diet containing soy protein concentrate (SPC) as a substitute for 50% FM protein was considered as a low‐FM diet (LFM). Three other diets contained three different sources of protein hydrolysates, including shrimp, tilapia, and krill hydrolysates (designated as SH, TH, and KH), replacing 12% of FM protein. All diets were formulated to be isonitrogenous and isocaloric. Triplicate groups of fish (15.1 ± 0.1 g) were handfed one of the diets to apparent satiation twice daily for 11 wk and subsequently challenged against Edwardsiella tarda. Growth performance and feed utilization of fish fed hydrolysate‐supplemented diets were significantly improved compared to those of fish fed the LFM diet. Dietary inclusion of the protein hydrolysates significantly enhanced apparent digestibility of dry matter and protein of the diets. In the proximal intestine, histological alterations were observed in the fish fed the LFM diet. The fish fed the hydrolysate diets showed significantly longer mucosal fold and enterocytes and greater number of goblet cells compared to fish fed the LFM diet. Respiratory burst activity was significantly higher in fish fed the TH and KH diets than fish fed the LFM diet. Significantly higher immunoglobulin levels were found in fish fed SH and KH diets compared to those of fish fed the LFM diet. Dietary inclusion of the protein hydrolysates in SPC‐based diets exhibited the highest lysozyme activity. Significantly higher superoxide activity was observed in groups of fish fed the KH diet. Fish offered the protein hydrolysates were more resistant to bacterial infection caused by E. tarda. The results of this study suggest that the tested protein hydrolysates can be used as potential dietary supplements to improve growth performance and health status of juvenile olive flounder when they were fed a LFM diet.