Effects of Dietary Protein and Lipid Levels on Growth and Body Composition of Juvenile Japanese Flounder,Paralichthys olivaceus,Fed Diets Containing Intact Proteins or Crystalline Amino Acids

Abstract

The influence of eight semi-purified diets having different protein and lipid levels on growth performance and body composition of Japanese flounder, Paralichthys olivaceus, was evaluated. The sources of protein were either intact protein (IP) or a mixture of IP and crystalline amino acids (CAA). In trial 1 (IP group), four test diets were prepared from IP sources (casein-gelatin) with combination of two protein levels (35% and 50%) and two lipid levels (10% and 20%). In trial 2 (PA-group), another four test diets were formulated using IP and CAA with combination of the same two protein and two lipid levels as used for trial 1. The juveniles (about 2.00 g initial weight) were fed the respective test diets for 42 days in duplicate tanks. In both trials, weight gain was the highest for juveniles fed the diet containing 50% protein with 10% lipid and the lowest in those fed the 35% protein with 10% lipid diet. Weight gain of juveniles was significantly increased when the lipid levels were increased in low protein (35%) diets for both trials. In high protein (50%) diet, however, increase lipid levels from 10 to 20% with 50% protein resulted in decrease in weight gain, irrespective of protein sources. Specific growth rate, feed intake, feed conversion efficiency were significantly affected by different dietary protein and lipid level. Content of neutral lipids in the whole-body particularly, triglycerides was statistically higher for fish fed the high-lipid diets than those fed the low-lipid diets irrespective of protein sources. But, polar lipid did not show any differences either for different protein or lipid levels. Level of individual amino acids in the whole-body showed little difference among the dietary treatments. Results suggest that Japanese flounder grew better on low lipid level with 50% protein-based diets and supplementation of CAA did not show any adverse effect on the growth performance with different levels of protein and lipid in the diets.     

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.     

Acute ammonia toxicity and gill morphological changes of Japanese flounder Paralichthys olivaceus in normal versus supersaturated oxygen

Ammonia toxicity and morphological changes in gills of juvenile Japanese flounder Paralichthys olivaceus (5.76 ± 0.12 g) were investigated when fish were separately exposed to normal dissolved oxygen (DO) at 6.5 ± 0.5 mg L^?1 and supersaturated oxygen at 16.0 ± 2.0 mg L^?1 at different ammonia concentrations. Under normal oxygen, ammonia concentrations were tested from 0.04 (control) to 93.3 mg L^?1 total ammonia nitrogen (TAN), whereas under oxygen supersaturation, ammonia concentrations ranged from 0.04 (control) to 226.7 mg L^?1 TAN in the trial. After exposure to ammonia for 96 h, the ammonia LC₅₀ for fish was 62.48 mg L^?1 TAN (0.50 mg L^?1 NH₃–N) at normal oxygen and 160.71 mg L^?1 TAN (0.65 mg L^?1 NH₃–N) at oxygen supersaturation. Light microscopic observations confirmed that gill damage in normal oxygen was more profound than in oxygen supersaturation when fish were exposed to the same level of TAN (93.3 mg L^?1). Furthermore, electron microscopic scanning also showed more crimple, retraction and fibrosis on the secondary lamella surface in fish exposed to normal oxygen than those in fish exposed to supersaturated oxygen at the same TAN (93.3 mg L^?1). This study suggests that supersaturated oxygen can increase ammonia tolerance in Japanese flounder through reducing gill damage by ammonia, which partially explains the merit of using pure oxygen injection in intensive fish farming.     

比较3种饲料对牙鲆生长和消化率的影响

选取平均体重为(359±16)g/尾的健康牙鲆48尾,随机分成3组,每组2个重复。采用3种不同饲料进行投喂,比较牙鲆专用配合饲料对牙鲆生长速度、饲料效率及消化率的影响。经过42d的饲养,结果表明:自配饲料(A组)增重速度最快、饲料系数最低,尾相对增重率达到230.1%、饲料系数达到1.59。牙鲆每增重1.0kg所需饲料成本最低,与B组、C组相比分别节省了13.7%和18.9%。A组的干物质消化率为81.56%,比B组、C组分别高5.33%和9.39%。A组的蛋白质消化率为91.17%,比B组、C组分别高3.26%和7.51%。     

Effects of dietary genistein administration on growth,survival and sex determination in southern flounder,Paralichthys lethostigma

The inclusion of soybean meal and soy concentrates in finfish feeds may introduce endocrine disrupting compounds in the form of phytoestrogens. Genistein, which may dually act as an oestrogen receptor agonist/antagonist, has been shown to elicit both masculinizing and feminizing effects in several teleost species. The objective of this investigation was to examine the effects of dietary genistein administration on reproductive development, growth and survival in southern flounder (Paralichthys lethostigma). Southern flounder received one of three experimental diets which contained varying concentrations of genistein (control – 0, low dose –100 and high dose –1000 mg genistein kg^?1 feed) from 84 to 153 days post hatch (DPH). Fish remained in culture until 285 DPH at which time sex ratios were determined. Growth and survival were evaluated at 153 and 285 DPH. Greater numbers of female fish resulted from the low and high dose genistein treatments (98 ± 2% and 78 ± 12% respectively), as compared to the control group (21 ± 10%). Reduced growth at 153 DPH and poor survival (28%) at 285 DPH were also observed for the high dose genistein treatment. Collectively, these results demonstrate the feminizing effects of genistein in southern flounder, but reduced growth and survival with high dietary administration.     

牙鲆抗迟缓爱德华菌病家系建立与抗病性能评价

为筛选出抗迟缓爱德华菌的牙鲆家系,实验以已经选育出的牙鲆抗病和快速生长家系以及从韩国引进的选育群体为亲本建立了牙鲆家系56个,并对其中32个家系进行了迟缓爱德华菌人工感染实验。确定了迟缓爱德华菌对牙鲆家系的半致死浓度LD50为3.69×105CFU/mL后,从每个家系中随机抽取75尾,按照0.2 mL/10 g体质量腹腔注射半致死浓度的菌液,并设置1次重复。人工感染时水温控制在(19±1)℃。从32个家系中共选取4 800尾5月龄牙鲆幼鱼进行感染,16 d实验结束后统计各家系存活率为8.2%~66.1%,平均存活率为31.2%。不同家系对迟缓爱德华菌的抗感染能力表现出显著差异(P0.05)。筛选出6个存活率高于45%的抗病家系,发现2007年筛选出的抗鳗弧菌病家系F0768的后代家系在迟缓爱德华菌感染后的存活率普遍很高,表现出抗迟缓爱德华菌病的能力。研究为选育抗鳗弧菌病和抗迟缓爱德华菌病的牙鲆优良品系奠定了基础,对牙鲆抗细菌病的分子机理研究及抗病新品种选育具有重要意义和应用价值。     

牙鲆主要生长性状与体质量的灰色关联度分析

采用灰色关联分析方法对牙鲆(Paralichthys olivaceus)10个选育家系的9个生长性状与体质量的关联度进行分析和评价。首先对体质量与生长性况进行数列无量纲化处理,计算出每个生长性状与体质量的关联系数和关联度,根据灰色关联度构建两两比较判断矩阵定量分析各生长性状对体质量的影响度。结果显示,每个生长性状与体质量的关联度由大到小依次为:全长(0.875 8)、体长(0.859 3)、尾柄高(0.830 7)、躯干长(0.827 7)、头长(0.803 5)、尾长(0.781 2)、体高(0.740 2)、吻长(0.665 7)和尾柄长(0.654 0)。体质量的主控因素为:全长、体长、尾柄高和躯干长4个性状,影响度分别为:28.51%、21.62%、16.41%和11.69%,四者的影响度总和达到78.23%。分析表明,与体质量关联度最大的分别是全长、体长、尾柄高和躯干长,且它们对体质量的影响度最高,可以将其作为培育高产牙鲆的重要评价指标,以提高选择效率。本研究旨在为制定理想的牙鲆选育目标、提高育种效率提供理论依据,同时拓展灰色关联度方法在水产动物育种研究中的应用。     

Pathogenicity of Edwardsiella tarda to olive flounder, Paralichthys olivaceus (Temminck & Schlegel)

The LD50 and cytotoxic and enzymatic activities of both cells and extracellular products (ECPs) of eight Edwardsiella tarda strains were determined and their bacterial superoxide dismutase gene (sodB) and catalase gene (katB) were sequenced. Strains were also examined for their ability to resist the immune responses of olive flounder, Paralichthys olivaceus. LD50 values of strains (FSW910410, KE1, 2, 3, 4, 5 and 6) in olive flounder ranged between 10(2.5) and 10(5.3) cfu (colony forming units) per fish. Unlike the avirulent strain SU100 (LD50>or=10(7)), all pathogenic strains were able to survive in flounder serum and head kidney leucocytes (except for KE2). The virulent strains possessed type I sodB and katB, whereas SU100 had type II sodB but not katB. However, there was no difference between avirulent and virulent strains in haemolytic and cytotoxic activities. The results of this study demonstrated that the ability of E. tarda to resist complement activity and phagocytosis is conferred by its superoxide dismutase and catalase, which thus play an essential role in the pathogenicity of this bacterium. In addition genotyping of sodB and kat B proved to be a very useful tool to distinguish virulent from avirulent strains.     

Susceptibility of marine fish species to a megalocytivirus, turbot iridovirus, isolated from turbot, Psetta maximus (L.)

Turbot iridovirus (TBIV), a member of the genus Megalocytivirus in the family Iridoviridae, was isolated from diseased turbot, Psetta maximus (L.), in Korea in 2003. In this study, experimental infection of turbot, Japanese flounder, Paralichthys olivaceus (Temminck & Schlegel), and rock bream, Oplegnathus fasciatus (Temminck & Schlegel), with TBIV was performed to evaluate the viral susceptibility of these fish species. After virus exposure, the mortalities of turbot reared at 22 and 25 degrees C were 60% and 100%, respectively, suggesting that TBIV is the causative agent of the mass mortality of turbot that occurred in Korea in 2003. Moreover, TBIV was detected in Japanese flounder and rock bream by polymerase chain reaction after experimental infection (26 days post-inoculation) despite no viral pathogenicity in these fish, suggesting that these two fish species are also susceptible to the virus. It is possible that horizontal transmission of TBIV occurs among these three fish species because turbot is routinely cultured with Japanese flounder and rock bream in Korea.     

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.