Juvenile tilapia (Oreochromis niloticus×Oreochromis aureus) requires dietary myo-inositol for maximal growth

An 8-week growth experiment was conducted to estimate the dietary requirement of myo-inositol (MI) for juvenile hybrid tilapia. MI was supplemented at 0, 150, 250, 350, 450, 600, and 1200 mg/kg diet in the basal diet providing 0, 167, 259, 367, 479, 612, and 1253 mg MI/kg diet. Basal diet without MI but with succinylsulfathiazole to suppress MI synthesis by intestinal bacteria was included for comparison. Each diet was fed to triplicate groups of tilapia (mean initial weight 0.51±0.01 g, n=3). Fish fed ≥367 mg MI/kg diet had significantly (P<0.05) higher weight gain, followed by fish fed 259 mg MI/kg diet, and lowest for fish fed the unsupplemented basal diet. Fish fed ≥367 mg MI/kg diet had higher feed efficiency than fish fed the basal diet. Supplementation of dietary inositol did not affect survival of tilapia. The MI concentrations in liver were highest in fish fed the ≥479 mg MI/kg diet, followed by fish fed the 259 and 167 mg MI/kg diets, and lowest in fish fed the basal diet. Hepatic lipid concentrations were higher in fish fed 367 mg MI/kg diet than fish fed ≤259 mg MI/kg diet. Weight gain percentage and MI concentrations in the liver for the different treatments were analyzed by broken-line regression and indicated that the requirement for dietary MI in growing tilapia is about 400 mg/kg diet. Addition of an antibiotic to basal diet did not affect the growth and hepatic inositol concentration of tilapia, suggesting that the intestinal microbial synthesis was not a significant source of inositol for tilapia.     

Digestibility and transit time of Azolla filiculoides Lamarck in Oreochromis aureus (Steindachner)

Azolla, an aquatic fern that is able to fix nitrogen directly from the atmosphere, could represent an interesting low-cost food for tropical fish. In the present study, the authors evaluated the apparent digestibility of Azolla filiculoides Lamarck by Oreochromis aureus (Steindachner), an omnivorous-phytoplankton-ophagous species of tilapia. Two digestibility tests (5 days) were performed in digestibility tanks on adult O. aureus fed only with dried A. filiculoides given ad libitum (2% biomass day^?1). Experiment 1 was made on fish weighing 28-49 g (duplicate) at a water temperature of 29 ± 0.5°C; experiment 2 was made on fish weighing 36-81 g (duplicate) at a water temperature of 27 ± 0.5°C. The transit time in O. aureus (weight: 30-50 g; water temperature: 27 ± 0.5°C) fed only and ad libitum with A. filiculoides was determined with methylene blue as a vital dye. The apparent faecal digestibility coefficients (%) obtained for dry matter and crude protein were 49.0 and 55.4%, respectively, in experiment 1, and 53.5 and 60.9% in experiment 2. The transit time values of 2.5-3.0 h and 3.0-3.5 h were obtained, respectively, for fresh and dried A. filiculoides. Thus, A. filiculoides shows relatively good digestibility values in O. aureus, which are comparable to those obtained with other aquatic plants in tropical fish. However, in order to meet the nutrient requirements of tilapias, Azolla has to be mixed with other foods.     

Effects of substituting fish meal with Azolla pinnata in practical diets for fingerling and adult Nile tilapia, Oreochromis niloticus (L.)

Abstract. Dry and fresh Azolla pinnata were evaluated as feed ingredients for fingerling and adult Nile tilapia, Oreochromis niloticus (L.). Dry Azolla was incorporated into practical diets containing approximately 30% crude protein and 360–400kcal/lOOg of GE lo replace 25,50,75 and 100% of the fish meal (FM) protein in the control diet. Fresh Azolla was also tested as a total diet for these fish. Formulated diets were fed to duplicate groups of fingerling (2–54g ± 0093) and adult (4033g ± 103) fish at a daily rate of 5% and 3% of their body weight respectively for 10 weeks. Growth and feed utilization efficiency of fish fed the control diet were significantly higher than of those fed Azolla-supplemented diets. Fish performance continued to deteriorate with increasing dietary Azolla level in the diets. This reduction was extremely sharp when dry and fresh Azolla were used as total diets. Furthermore, adult tilapia fed fresh Azolla started losing weight from the 7th week. Fish fed fresh Azolla had significantly higher moisture content than those fed formulated diets. Body protein and lipid contents were negatively correlated with Azolla levels in the diets, while body ash content showed a positive correlation. Results of this study indicate that young Nile tilapia utilizes Azolla more efficiently than the adults.     

Tol2-mediated transgenesis in tilapia (Oreochromis niloticus)

The Nile tilapia (Oreochromis niloticus) is an important species in aquaculture and an excellent model system for laboratory studies. Functional genetic analysis using this species has been difficult because existing methods for producing transgenics are inefficient. Here we show that the Tol2 transposon system can be used to create transgenic tilapia with high efficiency. We constructed a line that is transgenic for GFP under control of a Xenopus elongation factor 1α (EF1α) promoter. The germline transmission rate of the Tol2 construct to the first generation was about 30%, which is much higher than conventional methods. GFP expression was strong and ubiquitous in the embryos. Application of the Tol2 system for constructing transgenics in tilapia and related species will promote research in many areas, but will be especially useful for studies of evolutionary developmental biology in the cichlid fishes of East Africa.     

吉富罗非鱼生长过程中氮收支变化的研究

为充实有关鱼类研究数据,提供实际生产理论依据,研究了吉富品系尼罗罗非鱼（Oreochromis niloticus）从鱼种（18 g）生长至成鱼（180 g）过程中氮收支变化。试验为期73 d,每日饱食投喂并收集鱼粪,溶解氧质量浓度为8.0-6.0 mg·L-1,pH为 7.5-6.5,水温为24-30 ℃。在鱼均质量达到50 g、100 g和180 g时测定并计算当前生长阶段氮收支。结果表明,生长氮比例在养殖初期最高（64%）,养殖中期最低（47%）;粪氮比例在养殖中期最高（9%）,养殖初期和末期分别为5%和4%;排泄氮比例随鱼的生长而逐渐增加。此外,试验期间水中总氮增加速度在养殖中期减慢,养殖末期再次加快。     

吉富罗非鱼成鱼胆碱的最适需要量

选用初始体质量为(220.00±8.34) g的吉富罗非鱼(Oreochromis niloticus)360尾, 随机分成6组,每组3重复(每重复20尾), 于1 m×1 m×1.5 m池塘网箱中饲养。分别饲喂胆碱含量为97.80(对照组)、375.04、565.74、974.27、      1 409.81、1 824.35 mg/kg的半纯化饲料10周, 研究胆碱对吉富罗非鱼成鱼生长、饲料利用、鱼体营养组成、胆碱蓄积量及部分血液生化指标的影响。结果显示, 经过10周的饲喂, 饲料中添加胆碱可显著提高鱼体增重率、特定生长率和饲料效率(P<0.05); 降低肝脂肪含量(P<0.05), 提高肌肉脂肪含量(P<0.05); 显著升高肝胆碱蓄积量(P<0.05); 胆碱添加组血清甘油三酯(TG)和总胆固醇(T-CHO)显著高于对照组(P<0.05), 并随饲料胆碱含量增加呈现升高的趋势; 肝甘油三酯(TG)和总胆固醇(T-CHO)随着胆碱含量的增加而显著降低(P<0.05); 血清谷草转氨酶(ALT)、谷丙转氨酶(AST)和碱性磷酸酶(ALP)均随着饲料胆碱含量的增大而显著降低(P<0.05)。结果表明, 饲料中添加适量的胆碱可以改善吉富罗非鱼成鱼的生长性能, 提高饲料利用效率, 降低肝脂肪含量, 促进肝脂肪转运; 对特定生长率进行回归分析, 得出吉富罗非鱼成鱼对饲料中胆碱的最低需要量为506.43 mg/kg, 而对肝胆碱蓄积量回归分析得出的需要量为981.38 mg/kg。

     

Modulation of calcium uptake in cadmium-pretreated tilapia (Oreochromis mossambicus) larvae

Tilapia larvae were exposed to 0 (control), 50 (50-Cd) or 100 (100-Cd) μg l^-1 cadmium for 4 days and then transferred to cadmium-free fresh water for 3 days of detoxification. Total length and weight, calcium influx and total body calcium and cadmium content were examined at various times during detoxification. All the groups grew normally with regards to total length and body weight. Within the first 12h of detoxification the 50- and 100-Cd exposed groups released cadmium at the similar rate of about 24 ng mg^-1 h^-1 (or 140 ng larva^-1 h^-1). Later, however, this rate declined to only 4–16% of the initial level. Calcium influx in the control group showed a 10–26% increase during the detoxification period. Calcium influx in the 50-Cd group increased by about 280% and reached it peak at 12h. Calcium influx in the 100-Cd group increased by 440% and did not peak until 24h after transfer. After peaking, the influxes in both 50- and 100-Cd groups declined to the level of control at the end of the experiment. Calcium contents in 50- and 100-Cd groups increased more rapidly than that in control group within first 24h of the detoxification period. However the rate of increase in calcium content in three groups was the same after 24h. The changes in calcium influx appeared to be correlated with those in calcium content, and these suggested that tilapia larvae regulate the mechanism of calcium balance to compensate for the reduced calcium level in the body. This revised version was published online in July 2006 with corrections to the Cover Date.     

Buprofezin toxication implicates health hazards in Nile tilapia (Oreochromis niloticus)

The objective of this study was to investigate the toxic effects of buprofezin insecticide on Nile tilapia (Oreochromis niloticus). The fish were exposed to buprofezin at 100 mg/L for 28 days. Compared to control, activity of serum transferases and levels of urea and creatinine showed significant increases. Oxidative stress was recorded manifested by elevated levels of malondialdehyde (MDA), reduced concentrations of reduced glutathione (GSH) and inhibition of activities of superoxide dismutase (SOD) and catalase (CAT) in liver and kidney. Examination of peripheral RBCs revealed elevated frequency of micronucleated cell. Interleukin 1 beta (IL‐1β) gene was upregulated in liver, muscle and brain, while that of cyclooxygenase 2 (COX‐2) gene increased in liver and muscle, but not in brain. Histopathological alterations were recorded in liver, kidneys, brain, gills, pancreas, spleen, intestine, muscle and ovaries. The immunohistochemical detection of caspase‐3 in the liver revealed no differences between treated and control groups; however, the expression of inducible nitric oxide synthase (iNOS) was demonstrated in hepatocytes and hepatopancreas in buprofezin‐treated group compared to control. It has been concluded that the tissue damage induced by buprofezin in Nile tilapia is mediated by oxidative stress and inflammatory response but not by apoptosis.     

吉富品系尼罗罗非鱼（GIFT）摄食节律初探

用投喂添加色素的膨化颗粒饲料和观测排便相结合的方法,研究吉富品系尼罗罗非鱼(Genetic Improvement of Farmed Tilapias;GIFT)的摄食节律.结果发现,6个家系的吉富品系尼罗罗非鱼摄食具有明显的节律性,家系之间的摄食周期存在非常显著差异(P＜0.0001);t检验发现,各家系内摄食周期和排便周期的差异均不显著(P≥0.1097).回归分析发现,摄食周期对生长无显著的影响(P=0.8988),但与摄食量之间存在显著的线性关系(R2=0.9679,P=0.0004).对摄食节律聚类分析,6个家系可分为(1、2、6)、(3、4)、5共3个家系类别.该项研究能为GIFT的养殖投饵和进一步选育提供理论依据,为鱼类摄食节律研究提供方法上的参考.     

Neuroimmunological regulation of α-MSH release in tilapia (Oreochromis mossambicus)

This study describes the effects of IL-1 (interleukin 1) and LPS (bacterial endotoxin lipopolysaccharide) on the release of α-MSH (alpha melanocyte stimulating hormone) from the neurointermediate lobe (NIL) of the teleost Oreochromis mossambicus (tilapia). In vivo treatment of tilapia with IL-1 for 8 days led to a 49% inhibition of basal α-MSH release, measured by means of an in vitro micro-superfusion technique. The treatment did not affect the sensitivity of the tissue to TRH. In vitro, the release of α-MSH was inhibited by LPS in a dose dependent manner. In addition to its effects on the unstimulated release of the hormone, LPS also blunted the response to a TRH stimulation. Together with recent results obtained by others demonstrating the effects of (neuro-)peptides on immune parameters and the presence of cytokines in fish, the present data establish the bidirectional character of the communication between the immune and the (neuro-)endocrine systems in teleosts.

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Résumé Cette étude décrit les effets de l'IL-1 (interleukin 1) et du LPS (bacterial endotoxin lipopolysaccharide) sur la libération de α-MSH (alpha melanocyte stimulating hormone) par le lobe neurointermédiaire (NIL) d'un téléosteen Oreochromis mossambicus (tilapia). Le traitement in vivo du tilapia avec l'IL-1 pendent 8 jours conduit à une inhibition de 49% de la libération basale d'α-MSH mesurée à l'aide d'une technique in vitro de micro-superfusion. Ce traitement ne modifie pas la sensibilité du tissue au TRH. In vitro, la libération de α-MSH est inhibée par le LPS de manière dose-dépendante. En plus de ses effets sur la libération basale de α-MSH, le LPS bloque aussi la réponse à une stimulation par le TRH. Confrontés à des donnés récemment publiés montrant les effets de (neuro-)peptides sur les paramêtres immunitaires et la présence de cytokines chez les poissons, nos résultats établissent le caractère bidirectionnel de la communication entre le système immunitaire et les systèmes (neuro-)endocriniens.

     

Osmoregulatory actions of growth hormone in juvenile tilapia (Oreochromis niloticus)

Growth hormone (GH) effectively promotes seawater (SW) adaptation in salmonids, but little is known of its effect in tilapias. Experiments were performed to investigate the effects of recombinant eel GH (reGH) on osmoregulatory actions and ultrastructural features of gill chloride cells in juvenile tilapia, Oreochromis niloticus. Tilapia showed a markedly improved SW survival, when directly transferred from freshwater (FW) to 62.5% SW 24h after a single reGH injection (0.25 or 2.5 µg g^-1) or 3 reGH injections (0.25 µg g^-1 every other day). Plasma Na+ and Mg²⁺ levels were significantly reduced by reGH (0.25 and 2.5 µg g^-1) compared with saline injections; Ca²⁺ concentrations were reduced significantly by high dose of reGH (2.5 µg g^-1) after SW transfer. However, fish failed to survive more than 24h when directly transferred to 70% SW, although the fish treated with reGH could survive longer than the controls. When examined by electron microscopy, the chloride cells were identified as mitochondrion-rich and an extensive tubular system was induced by GH treatment. The results of the present study suggest that, similar to its effect on salmonids, GH also exerts acute osmoregulatory actions and enhances SW adaptation in juvenile tilapia. GH also stimulates the differentiation of chloride cells toward SW adaptation.     

尼罗罗非鱼卵黄脂磷蛋白的分离纯化与性质鉴定

采用Sephacryl S-300过滤层析和DEAE-Sepharose Fast Flow离子交换层析相结合的方法从尼罗罗非鱼(Oreochromis niloticus)成熟卵子匀浆液中分离纯化出了一种高分子量的蛋白。该蛋白能被Schiff试剂、甲基绿和苏丹黑B着色,Western blot显示能被金鱼卵黄脂磷蛋白(lipovitellin,Lv)多克隆抗血清特异性识别,在非变性条件下分子量约为560 k D,在SDS变性条件下分子量约为112 k D,结果表明分离纯化的蛋白是一种含有糖、磷、脂基团的蛋白,符合鱼类Lv的性质,且与金鱼Lv有免疫交叉反应,从蛋白的性质和免疫原性以及分子量大小等角度判断,本研究获得的高纯度蛋白为尼罗罗非鱼卵黄脂磷蛋白;纯化的罗非鱼Lv在反复冻融、37℃及60℃处理条件下均未出现降解,表明罗非鱼Lv比鱼类卵黄原蛋白(Vitellogenin,Vtg)更为稳定。研究结果为罗非鱼Lv抗体的制备奠定了基础。     

Dietary taurine improves reproductive performance of Nile tilapia (Oreochromis niloticus) broodstock

This study was conducted to evaluate the effects of supplemental taurine on reproductive performance of Nile tilapia (Oreochromis niloticus) broodstock fed soybean meal‐based diets. Four isonitrogenous (350 g kg^?1 protein), isocaloric (18 MJ kg^?1) diets were formulated to contain 0, 5, 10 and 15 g kg^?1 taurine. The diets were fed to triplicate groups of juvenile Nile tilapia (10–15 g average body weight) at a female: male ratio of 3 : 1, to apparent satiation, three times per day for 130 days. The size at first maturation decreased with increasing dietary taurine to 10 g kg^?1 and levelled off with further taurine supplementation. The time to first spawning was also significantly shorter at 10 g kg^?1 taurine level. Spawning performances, including spawning frequencies, total number of spawnings per tank, number of spawnings per female and absolute fecundity, were all significantly improved with increasing dietary taurine up to 10 g kg^?1. However, the quadratic regression analyses indicated that the maximum spawning performance occurred at 8 g kg^?1 of supplemental taurine. Eggs produced from broodstock fed 10 g kg^?1 taurine exhibited significantly higher hatchability and required shorter time for hatching and yolk‐sac absorption and also resulted in higher larval weight than at other dietary taurine levels. The highest egg protein, total amino acids and taurine were also obtained at 10 g kg^?1 taurine. These results suggest that 8 g kg^?1 dietary taurine is required for optimum reproductive outputs of Nile tilapia broodstock.     

Immuomodulatory effect of dietary turmeric supplementation on Nile tilapia (Oreochromis niloticus)

This study aimed to assess the immunomodulatory effect of dietary turmeric (TUM) in Oreochromis niloticus juveniles. A total of 240 Oreochromis niloticus fingerlings were divided into four equal groups (n = 60), three replicates (n = 20) for each: control and TUM‐treated groups at 2 (T1), 4 (T2) and 8 (T3) g kg^?1 diets for 8 weeks. Body weight gain, leucocytes counts, plasma levels of interleukin 2 (IL‐2), interleukin 4 (IL‐4), lymphocyte proliferation index to pokeweed mitogen (PWM), nitric oxide (NO) and lysozyme enzyme activities were measured. Histopathology of spleen was performed. TUM at 2 g kg^?1 significantly (p < .05) improved weight gain, leucocytes, NO and lysozyme activity than control and other treatment groups. IL‐2 level was significantly lower (p < .05) in T2 and T3 than in control and T1, while IL‐4 and lymphocyte proliferation index were significantly (p < .05) elevated in T3 than control, T1 and T2. Spleens of T2 showed improvement in white pulp, while spleen of T3 and T4 revealed white pulp depletion. In conclusion, TUM supplementation exerted immunomodulatory effect in Oreochromis niloticus through manipulation of lymphocyte count, IL‐2, IL‐4 and antibacterial enzymatic activity (NO and lysozyme) that resulted in higher weight gain. Increasing TUM supplementation of fish diets beyond 2 g kg^?1 was not beneficial.     

Detection of tilapia lake virus (TiLV) infection by PCR in farmed and wild Nile tilapia (Oreochromis niloticus) from Lake Victoria

Tilapia lake virus disease (TiLVD) has emerged to be an important viral disease of farmed Nile tilapia (Oreochromis niloticus) having the potential to impede expansion of aquaculture production. There is a need for rapid diagnostic tools to identify infected fish to limit the spread in individual farms. We report the first detection of TiLV infection by PCR in farmed and wild Nile tilapia from Lake Victoria. There was no difference in prevalence between farmed and wild fish samples (p = .65), and of the 442 samples examined from 191 fish, 28 were positive for TiLV by PCR. In terms of tissue distribution, the head kidney (7.69%, N = 65) and spleen (10.99%, N = 191), samples had the highest prevalence (p < .0028) followed by heart samples (3.45%, N = 29). Conversely, the prevalence was low in the liver (0.71%, N = 140) and absent in brain samples (0.0%, N = 17), which have previously been shown to be target organs during acute infections. Phylogenetic analysis showed homology between our sequences and those from recent outbreaks in Israel and Thailand. Given that these findings were based on nucleic acid detection by PCR, future studies should seek to isolate the virus from fish in Lake Victoria and show its ability to cause disease and virulence in susceptible fish.     

Glycerol inclusion in the diet of Nile tilapia (Oreochromis niloticus) juveniles

The present study evaluated the effects of inclusion of glycerol in the diet of Nile tilapia juveniles on growth performance, biochemical changes in blood, and carcass composition. We used 300 Nile tilapia juveniles with an average initial weight of 29.15 ± 8.40 g and 11.55 ± 0.87 cm in length, distributed in 20 fiberglass tanks with a capacity of 250 L. The experiments followed a completely randomized design with five treatments and four replications during 79 days. The animals were fed diets containing four concentrations of glycerol (25 g kg^?1, 50 g kg^?1, 75 g kg^?1 and 100 g kg^?1) and a control diet without glycerol. HDL was the only biochemical parameter, that showed statistically different (P < 0.05) results; it was higher in the groups fed with 0 and 75 g kg^?1 glycerol compared to the other groups. No significant difference was observed in the results from the carcass composition of tilapia juvenile fed with the different glycerol levels, except for lipids (P < 0.05), which showed the highest values in fish fed with 50 g kg^?1 glycerol and the lowest in fish fed with 100 g kg^?1. Glycerol can be used in fish diets as an energy supplement without causing damage to growth performance or to the biochemical and carcass composition of Nile Tilapia juveniles.     

Apparent digestibility coefficients of feed ingredients and their prediction in diets for tilapia Oreochromis niloticus×Oreochromis aureus (Teleostei, Cichlidae)

Apparent digestibility of crude protein (CP), lipid, carbohydrate, energy and fatty acids was measured in various feed ingredients fed to hybrid tilapia (Oreochromis niloticus×Oreochromis aureus) including fish and poultry meals, corn gluten, soybean meal, rapeseed meal, sunflower seed meal, wheat, corn, sorghum, barley and wheat bran. Chromic oxide was used as a non‐absorbed marker. A diet compounded from a mixture of these ingredients was then used to examine the possibility of predicting the digestibility of formulated diets. In addition, the effect of pelleting or extrusion on digestibility of a compound diet was examined. Apparent digestibility of CP ranged from 75% to 97%, lipids from 72% to 90% and energy from 39% to 89% in the different ingredients. Apparent digestibility of carbohydrates was lower and ranged from 32% to 80%. Digestibility of fatty acids ranged from 75% to 90% with saturated fatty acids exhibiting digestibilities lower than unsaturated fatty acids. In a full‐fat soy diet containing 19% fat, digestibility of lipids did not decrease. There were no significant differences in digestibility between a diet that was either pelleted or extruded. Tests conducted using a compound diet indicated that ingredient digestibility was additive for protein, lipids carbohydrates and energy. Diets for the hybrid tilapia may thus be formulated on the basis of digestibility of individual ingredients, for the nutrients examined in this study.