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Dietary glutamine improves the function of erythrocytes through its metabolites in juvenile carp (Cyprinus carpio var. Jian)

Published on 29/4/2017
Publication date: 1 May 2017
Source:Aquaculture, Volume 474

Author(s): Hua-Tao Li, Wei-Dan Jiang, Yang Liu, Jun Jiang, Yong-An Zhang, Pei Wu, Yun-Yun Zeng, Xiao-Qiu Zhou, Lin Feng

An 8-week feeding trial was conducted to determine the effect of dietary glutamine (Gln) on the erythrocyte function in juvenile Jian carp. The results indicated that dietary Gln caused significant increases in haematocrit, erythrocyte count, haemoglobin concentration, mean corpuscular volume and mean corpuscular haemoglobin content in carp blood. Dietary Gln caused significant decreases in the levels of superoxide anion, hydrogen peroxide, met-haemoglobin, malonaldehyde and protein carbonyl and increases in the level of reduced glutathione and the activities of Na+, K+-ATPase and lactate dehydrogenase in carp erythrocytes. These results demonstrated that dietary Gln could improve the function of erythrocytes in fish. Meanwhile, the present study explored the effect of dietary Gln on hydroxyl radical (OH)-induced apoptosis in carp erythrocytes. We found that dietary Gln prevented the OH-induced apoptosis by inhibiting the generation of reactive oxygen species and the oxidation of cellular components, and restoring the non-enzymatic and enzymatic antioxidant activities in fish erythrocytes. These results revealed that the effects of Gln on the function may be closely associated with apoptosis in fish erythrocytes. Moreover, our data suggested that dietary Gln raised the levels of alanine (Ala), citrulline (Cit) and proline (Pro) in plasma of carp. We then examined the protective effects of Ala, Cit and Pro at the physiological concentrations in OH-induced carp erythrocytes. The results indicated that Ala, Cit or Pro at the physiological concentrations suppressed apoptosis and the oxidation of cellular components, and restored the GSH antioxidant system in the OH-induced carp erythrocytes. Moreover, the combination of Ala, Cit and Pro at the physiological concentrations produces a greater protective effect than their individual effects in fish erythrocytes. These results displayed that the effects of Gln on erythrocytes are at least partly dependent on that of its metabolites in fish. Ala, Cit, Pro and their combination could serve as an antioxidant or apoptosis-inhibitor in fish.





Effects of dietary soy protein concentrate meal on growth, immunity, enzyme activity and protein metabolism in relation to gene expression in large yellow croaker Larimichthys crocea

Published on 29/4/2017
Publication date: Available online 26 April 2017
Source:Aquaculture

Author(s): Ping Wang, Junquan Zhu, Jian Feng, Jiaojiao He, Yudong Lou, Qicun Zhou

A 56-day feeding trial was conducted to investigate the effects of dietary soy protein concentrate meal (SPC) levels on growth performance, body composition, antioxidant and immune responses, enzyme activities and protein metabolism in relation to gene expression in Larimichthys crocea (initial weight 10.50±0.04g). Five isonitrogenous and isolipidic diets (45% protein and 10% lipid) were formulated by replacing 0 (the control), 25%, 50%, 75%, and 100% of fish meal protein with SPC protein (designed SPC0, SPC25T, SPC50T, SPC75T and SPC100T, respectively). Lysine and methionine were added to the feed except the control diet, and the levels in the treatment diets were the same. Each diet was randomly fed twice daily (05:00 and 17:00) to apparent satiation to triplicate groups (60 fish per cage). The survival rate (SR) ranged from 90.56 to 93.89%, with no significant differences observed among dietary treatments (P >0.05). In addition, no significant differences were found for weight gain ratios (WGR), specific growth rates (SGR), feed conversion ratios (FCR) and feed intakes (FI) (P >0.05). Fish muscle protein and moisture contents did not show any statistical differences among the dietary treatments (P >0.05). Lipid contents first increased and then decreased, and the SPC25T diet was the highest. Ash contents first decreased and then increased, and the SPC100T diet was the highest. Fish whole-body composition analysis showed that with increasing dietary SPC levels, protein contents did not show any statistical differences among the dietary treatments (P >0.05). Lipid contents were significantly lower of SPC100T than SPC0 and SPC25T diets (P <0.05), and the highest was in the SPC0 diet. The contents of moisture in SPC100T diet were observed the highest, and significantly higher than the control diet (P <0.05). Ash contents of SPC50T diet were significant higher than SPC0 and SPC25T diets (P <0.05), but no significant differences were found among the diets of SPC50T, SPC75T and SPC100T (P >0.05). Significantly lower liver total superoxide dismutase (t-SOD) activity was found for the SPC100T diet than the SPC25T and SPC50T diets (P <0.05). There were no significant differences among the dietary diets with regard to malondialdehyde (MDA), catalase (CAT), and (glutathione peroxidase) GPx (P >0.05). Serum lysozyme (LYZ) activity was significantly lower in the SPC100T diet than in the SPC25T and SPC75T diets (P <0.05). There were no significant differences among the diets for alkaline phosphatase (AKP), complement C3 and C4 (P >0.05). Regarding digestive enzymes, no significant differences were found for hintgut alpha-amylase and lipase activity between the dietary treatments and the control diet (P >0.05). Among all diets, trypsin activity was the highest in fish fed the SPC75 diet, and significantly higher than SPC50T (P <0.05), but there were no significant differences among the SPC0, SPC25T, SPC75T and SPC100T diets (P >0.05). For liver protein metabolism enzymes, no significant differences were found in alanine aminotransferase (ALT) and aspartate amino-transferase (AST) among all dietary diets (P >0. 05). With increasing dietary SPC levels, hepatic insulin-like growth factor-I (IGF-I) expression decreased, and significant differences were observed between SPC50T, SPC75T, SPC100T and the control diets (P <0.05). Target of rapamycin (TOR) expression in the liver decreased, and there were significant differences between the treatment and the control diets (P <0.05). In conclusion, the results of this study suggest that SPC can completely replace fish meal protein as feed for large yellow croaker with no significant negative effects on growth performance.





The influence of dietary arachidonic acid on growth, reproductive performance, and fatty acid composition of ovary, egg and larvae in an anabantid model fish, Blue gourami (Trichopodus trichopterus; Pallas, 1770)

Published on 29/4/2017
Publication date: 1 July 2017
Source:Aquaculture, Volume 476

Author(s): Shima Masoudi Asil, Abdolmohammad Abedian Kenari, Ghodrat Rahimi Miyanji, Glen Van Der Kraak

This study investigates the influence of arachidonic acid (ARA) on growth, reproductive performance, and fatty acid compositions of ovary, egg and 3-DPH (days post hatching) larvae of Trichopodus trichopterus broodstock. A 150-day feeding experiment was performed comparing the effects of five ARA-supplemented diets containing 0 (control), 0.5, 1, 1.5 and 2% ARA (of total fatty acids) (TFA). Growth parameters including final weight, weight gain and specific growth rate (SGR) did not differ between different groups (P >0.05). Feed conversion ratio (FCR) was significantly lower in control group compared to 0.5 and 1.5% ARA groups (P <0.05). Contrary to growth indices, all reproductive traits were significantly affected by ARA contents in diets. Absolute and relative fecundities increased in relation to the ARA content (P <0.05). The maximum absolute and relative fecundities (13.3 and 974.3×103, respectively) were recorded in 2% ARA treatment group (P <0.05). Mean oocyte diameter reached the greatest size (861.66μm) in 1% ARA and was significantly different than other treatments (P <0.05). The yolk sac diameter was enhanced linearly by increasing dietary ARA (P <0.05). Results showed striking effects of dietary ARA on its accumulation in ovaries, eggs and larva. Ʃ n6 series fatty acid (44.9%) and its constituent (18:2n6) (40.85%) reached the highest contents in 0.5% ARA in ovaries (P <0.05). A similar trend was seen in fertilized eggs and 3-DPH larvae in that the highest amounts of 18:2-6 and Σ n6 were found in the 0.5% ARA group (P <0.05). A second order polynomial regression was employed for estimating ARA/EPA (eicosapentaenoic acid) ratios and showed that the respective ratio enhanced linearly in the ovary and fertilized egg. Correspondingly, ARA/DHA (docosahexaenoic acid) ratio in ovary, fertilized egg and larvae reflected those of the experimental diets. Their fatty acid profiles reflect the diet composition well, ovary (R2 =0.87), fertilized egg (R2 =0.91) and 3DPH larvae (R2 =0.82) and the ARA/DHA ratios were linearly improved by increasing dietary ARA (P <0.05). Overall, the results of this study revealed the necessity of ARA inclusion in T. trichopterus broodstock diets. This conclusion challenges the generally accepted hypothesis that freshwater fish meet their highly unsaturated fatty acids (HUFA) requirements by elongation and desaturation their precursors. These findings showed that T. trichopterus broodstock, as a model of asynchronous multi-batch spawning fish, needs to receive at least 1% ARA in their maturation diet to improve reproductive performance. The best efficiency was achieved in 2% ARA, based on fecundity, yolk sac diameter and hatching rate.





Finishing diet, genetics, and other culture conditions affect ovarian adiposity and caviar yield in cultured white sturgeon (Acipenser transmontanus)

Published on 29/4/2017
Publication date: 1 May 2017
Source:Aquaculture, Volume 474

Author(s): Daphne A. Gille, Joel P. Van Eenennaam, Thomas R. Famula, Andrea D. Schreier, Ken Beer, Peter Struffenegger, Bobby Renschler, Shaoching Bishop, Serge I. Doroshov

The on-going and precipitous decline in sturgeon abundance and increased demand for caviar have promoted the development of sustainable sturgeon aquaculture. One common problem that confounds caviar farming efficiency is highly variable roe yield associated with the proliferation of ovarian fat: sturgeon females with fatty ovaries tend to produce a smaller yield of inferior quality roe compared to those with lean ovaries. Here, we evaluated the effects of finishing diet, farm origin, age at maturity, tank, and genotype on ovarian adiposity and caviar yield in cultured white sturgeon (Acipenser transmontanus). We conducted a feeding trial in which fish aged 5+years at two different commercial farms were either maintained on a high fat production diet or received a low fat finishing diet for 19 and 33months before caviar harvest; at this time fish were aged 7 or 8years, respectively. Measurements of ovarian fattiness, caviar yield, and morphology were collected at the time of harvest. Microsatellite genotyping was performed to estimate relatedness among experimental fish and subsequent heritability of these traits. Mean caviar yield normalized by body weight increased from 7.6–8.6% to 8.0–9.2% and mean caviar yield scaled by ovary weight increased from 55.5–59.8% to 61.3–64.6% in white sturgeon fed the high and low fat diets, respectively. All females were classified post hoc according to degree of ovarian fattiness: low, medium, or high. Regardless of diet, farm, or age, females in the high ovarian adiposity group had larger body size, higher condition factor, but lower caviar yields than those in the low fattiness group because of the presence of large ovarian fat lobes and adipocytes surrounding individual oocytes. Furthermore, only 11.8–17.2% of female white sturgeon given the low fat finishing diet displayed a high degree of ovarian fattiness compared to 18.0–33.2% of those on the high fat diet. Robust negative correlations were found between measurements of ovarian adiposity and caviar yield further illustrating this inverse relationship observed by caviar farmers. The fixed effects of diet, farm, age, and tank all significantly influenced ovarian adiposity and caviar yield except farm origin did not significantly impact ovarian fat lobe weight. Heritability values for measurements of ovarian adiposity and caviar yield were moderate and ranged from 0.20–0.39, however heritability of ovarian tissue weight was slightly lower (h 2 =0.11). Our study demonstrates that finishing diet, farm origin, age at maturity, tank and genotype significantly affect and may be manipulated to increase caviar yield in cultured white sturgeon. Statement of relevance Study findings will increase sturgeon aquaculture profits.





Bayesian latent class analysis of diagnostic sensitivity and specificity of tests for surveillance for bacterial kidney disease in Atlantic salmon Salmo salar

Published on 29/4/2017
Publication date: 1 July 2017
Source:Aquaculture, Volume 476

Author(s): Diana Jaramillo, Ian A. Gardner, Henrik Stryhn, Holly Burnley, K. Larry Hammell

Bacterial kidney disease (BKD) diagnosis is often carried out by IFAT, ELISA, and PCR because these tests yield rapid results compared with bacterial culture for the causative agent, Renibacterium salmoninarum. However, the diagnostic sensitivity (DSe) and specificity (DSp) of these tests is generally unknown, particularly in subclinically infected Atlantic salmon. Bayesian models were used to analyse test results from 454 field samples sourced from salmon populations with different infection status and submitted to independent laboratories. Results showed that DSe was highly dependent on the presentation of infection. When applied to fish with BKD-associated gross lesions, the highest to lowest posterior medians for DSe were: PCR2 (0.98), PCR1 (0.97), bacterial culture (0.86), ELISA (0.82) and IFAT (0.75). When applied to fish without lesions, the posterior medians for DSe were: PCR1 (0.82), PCR2 (0.82), bacterial culture (0.29), IFAT (0.29) and ELISA (0.21). The posterior medians for DSp were similar in populations with and without lesions. ELISA had the highest DSp (0.99), followed by culture (0.98–0.99), IFAT (0.96), PCR1 (0.94–0.96) and PCR2 (0.83–0.84), where different numbers reflect the estimates for populations with or without lesions respectively. Among tests that were evaluated for intra-laboratory repeatability (ELISA, PCR1 and IFAT), ELISA had the highest repeatability (kappa=0.82). We concluded that PCR tests were the fittest of the evaluated tests for the purpose of screening subclinically-infected adult Atlantic salmon.





Growth and oxidative parameters of Rhamdia quelen fed dietary levels of vitamin A

Published on 29/4/2017
Publication date: 1 May 2017
Source:Aquaculture, Volume 474

Author(s): Eduardo K. Battisti, Samuel Marasca, Emerson G. Durigon, Valesca S. Villes, Thamara L.S. Schneider, Juliano Uczay, Nilce C. Peixoto, Rafael Lazzari

Vitamin A, a fat soluble compound is an essential nutrient for fish. The present study evaluated the effects of dietary vitamin A administered to juvenile silver catfish (Rhamdia quelen). Fish were fed semi-purified diets formulated to meet the protein and energy requirements of the species (37% CP and 3400kcalkg1 DE). Five vitamin A levels were tested: 1090, 1180, 1750, 2610 or 2880IUkg1 of diet. The growth, body composition, metabolic and blood parameters and oxidative stress biomarkers of juvenile silver catfish were studied after 70days. Fish growth increased with an increase in vitamin A. The fish that were fed a 2610IUkg1 vitamin A diet had better quality fillets, with more protein and less fat. No effects on hematological and biochemical parameters were noted. The high levels (1750, 2610 and 2880IUkg1) of vitamin A improved the fish antioxidant defense system. Lower activity was observed for enzymes that act as antioxidants because retinoids and carotenoids acted as scavengers and donated electrons to reactive oxygen species, conferring enzymatic protection and contributing to the animal's energy economy. Based on the growth and fillet quality and oxidative results, we recommend a 2610IUkg1 vitamin A diet for juvenile R. quelen. Statement of relevance Important to assess the nutrition and health of the silver catfish.





A workflow used to design low density SNP panels for parentage assignment and traceability in aquaculture species and its validation in Atlantic salmon

Published on 29/4/2017
Publication date: 1 July 2017
Source:Aquaculture, Volume 476

Author(s): Luke E. Holman, Daniel Garcia de la serrana, Aubrie Onoufriou, Borghild Hillestad, Ian A. Johnston

Accurate parentage assignment is key for the development of a successful breeding program, allowing pedigree reconstruction from mixed families and control of inbreeding. In the present study we developed a workflow for the design of an efficient single nucleotide polymorphism (SNP) panel for paternity assignment and validated it in Atlantic salmon (Salmo salar L.). A total of 86,468 SNPs were identified from Restriction Site Associated DNA Sequencing (RAD-seq) libraries, and reduced to 1517 following the application of quality control filters and stringent selection criteria. A subsample of SNPs were chosen for the design of high-throughput SNP assays and a training set of known parents and offspring was then used to achieve further filtering. A panel comprising 94 SNPs balanced across the salmon genome were identified, providing 100% assignment accuracy in known pedigrees. Additionally, the panel was able to assign individuals to one of three farmed salmon populations used in this study with 100% accuracy. We conclude that the workflow described is suitable for the design of cost effective parentage assignment and traceability tools for aquaculture species.





Multifactorial interactions and optimization in biomass harvesting of marine picoalga Picochlorum maculatum MACC3 with different flocculants

Published on 29/4/2017
Publication date: 1 May 2017
Source:Aquaculture, Volume 474

Author(s): Arun Augustine, Jisha Kumaran, Jayesh Puthumana, Sanyo Sabu, I.S. Bright Singh, Valsamma Joseph

Cost effective harvesting of biomass is a major challenge in microalgal industries as it involves the recovery of small sized algal cells from large volumes of culture medium. The present work evaluated the potential of chitosan and aluminium sulfate (AS) in the flocculation of the marine picoalga, Picochlorum maculatum MACC3 using response surface methodology based optimization of flocculation conditions. The viability and integrity of the flocculated cells were assessed using Evan's blue staining and scanning electron microscopy. Under optimized conditions, flocculation efficiency of >95% was achieved with a chitosan concentration of 63mgL1 at pH8.5, and aluminium sulfate concentration of 150mgL1 at pH9.7 with algal biomass concentration of 1.5gL1. Based on flocculation efficiency, cell viability and cell integrity chitosan was selected as an efficient flocculant for biomass harvesting of P. maculatum. The flocculated biomass of this newly isolated nutritionally rich microalga can be further explored for feed applications in aquaculture after accomplishing studies under laboratory and field conditions.





Emergence of tilapia lake virus in Thailand and an alternative semi-nested RT-PCR for detection

Published on 29/4/2017
Publication date: 1 July 2017
Source:Aquaculture, Volume 476

Author(s): H.T. Dong, S. Siriroob, W. Meemetta, W. Santimanawong, W. Gangnonngiw, N. Pirarat, P. Khunrae, T. Rattanarojpong, R. Vanichviriyakit, S. Senapin

The present study reports outbreaks of tilapia lake virus (TiLV), an emerging pathogen causing syncytial hepatitis of tilapia (SHT), in farmed tilapia in Thailand. Occurrence of the virus was confirmed by RT-PCR and nucleotide sequence homology to the TiLV from Israel. Diseased fish exhibited typical histopathological features of syncytial giant cells in the liver examined through H&E and semi-thin sections. Presence of intracytoplasmic viral particles was revealed by TEM. In situ hybridization using a specific DIG-labeled probe derived from a partial genome segment 3 of TiLV genome revealed multiple tissues tropism of the virus including liver, kidney, brain, spleen, gills and connective tissue of muscle. An alternative semi-nested RT-PCR protocol has been developed in this study for disease diagnosis. Additionally, comparative genetic analysis revealed genetic variations of Thailand-originated virus to the Israel TiLV strains, sharing 96.28 to 97.52% nucleotide identity and 97.35 to 98.84% amino acid identity. Outbreaks of TiLV in different continents might signal a serious threat to tilapia aquaculture globally.





Comparison of carbohydrate metabolism key enzymes in different generations of growth-selected Portunus trituberculatus families

Published on 29/4/2017
Publication date: Available online 28 April 2017
Source:Aquaculture

Author(s): Zhuqing Wang, Xianyun Ren, Baoquan Gao, Xuan Yu, Xiaohui Zhang, Jie Zhang, Ping Liu

The aim of the present study was to evaluate the possible effects of inbreeding on the carbohydrate metabolism of Portunus trituberculatus juveniles from different inbred families by measuring the activities of carbohydrate metabolism-related enzymes and glycogen content. The results show that inbreeding weakens the activities of hexokinase in the hepatopancreas and muscle; pyruvate kinase, muscles and serum; and lactate dehydrogenase, gills, but enhances the activity of succinate dehydrogenase in the muscles and gills. The real-time PCR results indicated that the relative mRNA expression levels of the metabolism-related genes decreased as the inbreeding generations increased. The results illustrate that inbreeding gradually reduces carbohydrate metabolism in P. trituberculatus.





Heritability estimates for shell color-related traits in the golden shell strain of Pacific oyster (Crassostrea gigas) using a molecular pedigree

Published on 29/4/2017
Publication date: 1 July 2017
Source:Aquaculture, Volume 476

Author(s): Sai Wan, Qi Li, Ting Liu, Hong Yu, Lingfeng Kong

The Pacific oyster (Crassostrea gigas) is an important aquatic animal species with enormous production and economic benefits, but heritability estimation for shell color applying mixed-family approach and computer vision system has not been performed. In this study, heritability for shell color-related traits was estimated in the golden shell strain of Pacific oyster by fostering a single cohort of 30 families in a nested mating design consisting of 10 sires and 30 dams. After parentage assignment inference based on six microsatellite markers, 690 offspring were included in the subsequent analyses. Using an animal model, at 16months of age, heritability estimates were 0.10±0.12 for L , 0.41±0.16 for a , 0.23±0.15 for b and 0.33±0.19 for ΔE. Genetic correlation between shell color-related traits and growth-related traits were generally inconspicuous ranging from −0.02 to 0.11. Conclusions can be obtained from our study that favourable improvement in aquatic selective breeding would be predictable for the genetic potential of the golden shell color in this strain of Pacific oyster, whereas independent selection conducted at the same time rather than correlative selection would be feasible in the improvement of both types of traits.





Toxicity and parasiticidal in vivo and in vitro evaluation of acetic acid on metazoan ectoparasites in juvenile Mugil liza

Published on 29/4/2017
Publication date: 1 July 2017
Source:Aquaculture, Volume 476

Author(s): Mário Roberto Castro Meira-Filho, Victor Torres Rosas, Rogério Tubino Vianna, Joaber Pereira Júnior

In this study, the anti-parasitic activity of acetic acid was evaluated in vivo and in vitro in juveniles of Mugil liza. The parasites studied were the copepods Ergasilus lizae and E. versicolor and the monogenoideans Solostamenides cf. platyorchis and Ligophorus spp. To determine concentrations for use in the in vivo evaluation, and to determine the therapeutic index, a toxicity test (LC50-1h) was carried out using juveniles of M. liza. The LC50-1h was estimated at 1402.62mgL1. Glacial acetic acid concentrations were determined for in vivo evaluation from the values of 0%, 25%, 50% and 75% of LC50-1h, which corresponded to concentrations of 0mgL1 (control), 350.65mgL1, 701.31mgL1 and 1051.96mgL1, respectively. Due to high mortality, fish exposed to 701.31mgL1 and 1051.96mgL1 concentrations were not examined in the in vivo evaluation. The results of the in vivo evaluation were presented in parasitic indexes of prevalence (P%), mean infestation intensity (MII) and mean abundance (MA). The MA values were used to determine the efficacy of the 350.65mgL1 concentration for each parasite found, which was 100% for S. cf. platyorchis, 91.47% for Ligophorus spp. and 73.57% for E. lizae. No specimens of E. versicolor were found in the in vivo evaluation. The in vitro evaluation comprised toxicity tests (EC50-1h) for each parasite taxa. The EC50-1h values were 83.38mgL1 for E. lizae, 89.97mgL1 for E. versicolor, 144.79mgL1 for S. cf. platyorchis and 289.58mgL1 for Ligophorus spp. With the values of LC50-1h of M. liza and EC50-1h values of each parasite taxa, the therapeutic indices were calculated, ranging from 16.82 for E. lizae, 15.59 for E. versicolor, 9.69 for S. cf. platyorchis and 5.53 for Ligophorus spp. It is possible that the presence of parasites affected the survival of the fish during in vivo evaluation. Although E. lizae presented the highest therapeutic index, it was the taxon that presented the lowest efficacy, probably due to the strong adhesion in the gills by its modified antennas, even after the death of the parasite. It has been found that glacial acetic acid at a concentration of 350.65mgL1 is an effective drug against M. liza parasites.





Plastic responses by wild brown trout (Salmo trutta) to plant-based diets

Published on 29/4/2017
Publication date: 1 July 2017
Source:Aquaculture, Volume 476

Author(s): Stéphanie Céline Michl, Benjamin Weis, Jeffrey A. Hutchings, Carsten Schulz

Decreasing fishmeal availability and increasing prices promote the usage of plant-derived feedstuff as a substitution for fishmeal in commercial salmonid diets. However, little is known about the impact of plant-derived feedstuff on juvenile brown trout (Salmo trutta), a species that exhibits strong phenotypic plasticity with various genetic sub-structures and high overall genetic diversity. Thus, the production of brown trout for restocking purposes preferentially uses wild fish as broodstock to avoid loss of genetic variability. Because of nutritional programming, the strictly carnivorous feeding habit of wild brown trout broodfish could nevertheless have a negative impact on the digestive physiology of fry and fingerlings that are fed with commercial plant-protein containing trout diets. The present study, therefore, investigated whether the feeding of plant-based diets from first feeding onwards induced a permanent improvement in the utilisation of plant-derived protein sources in wild brown trout juveniles. Any plastic responses to the experimental diets resulting in a long-term physiological effect were hypothesised to be not only observed in growth performance, but also in altered pepsin and amylase activities. We demonstrated that (i) the feeding of wild brown trout fry with inclusion levels of up to 50% of dietary plant proteins is beneficial during the first weeks of life and (ii) continuous feeding of at least 50% plant-derived dietary protein resulted in the same rate of growth when compared to the growth resulting from fishmeal as the exclusive dietary protein source. Pepsin and amylase activities were only partly affected by diet-type and it can be concluded that intestinal pepsin and amylase activities in juvenile brown trout are primarily regulated by intrinsic mechanisms. In the present experiment, we were not able to induce a permanent nutritional programming effect of the first feeding diet; instead, a cross-over diet change applied 89days post first feeding demonstrated that wild brown trout fry exhibit highly plastic responses to different feeding strategies during the first months of life.





Cloning, tissue expression of the fatty acid-binding protein (Pt-FABP1) gene, and effects of dietary phospholipid levels on fabp and vitellogenin gene expression in the female swimming crab Portunus trituberculatus

Published on 29/4/2017
Publication date: 1 May 2017
Source:Aquaculture, Volume 474

Author(s): Li-Yun Ding, Min Jin, Peng Sun, You Lu, Hong-Na Ma, Ye Yuan, Hui-Yun Fu, Qi-Cun Zhou

In the present study, the cDNA of fatty acid-binding protein (Pt-FABP1) from the hepatopancreas of swimming crab (Portunus trituberculatus) was cloned by rapid amplification of cDNA ends (RACE) approaches. The full-length cDNA of Pt-fabp1 was 730bp and encoded a 130 amino acids polypeptide that was highly homologous to related genes from other crustacean. Quantitative PCR analysis revealed that Pt-fabp1 expression was detected in various tissues, and the highest expression levels was occurred in the hepatopancreas. The Pt-fabp1 expression levels in the ovary would depend on the stages of ovarian development, and the expression of Pt-fabp1 reached the maximum at the stage IV. The effects of dietary soybean lecithin (SL) on the Pt-fabp1 and vitellogenin (VTG) expression, and steroid hormones levels were investigated. After 16weeks of feeding, the results showed that the expression level of Pt-fabp1 in hepatopancreas and the content of progesterone (PG) in hemolymph did significantly increase with dietary SL supplementation up to 2% (P <0.05). Swimming crab fed the diet containing 4% SL had higher hepatopancreas vtg gene expression and the content of 17 β-estradiol (E2) in hemolymph than those fed the control diet (P <0.05). This study suggested that Pt-FABP may have a positive function in ovary maturation of female swimming crab. Meanwhile, these results not only demonstrated that the gene expression of Pt-fabp1 and vtg in hepatopancreas can be modulated by dietary SL levels, but also clearly supported the hypothesis that the positive effects of dietary SL on the ovarian development of female swimming crab.





Dietary selenium requirement of juvenile oriental river prawn Macrobrachium nipponense

Published on 29/4/2017
Publication date: 1 July 2017
Source:Aquaculture, Volume 476

Author(s): Youqin Kong, Zhili Ding, Yixiang Zhang, Jinyun Ye, Zhenyu Du

Selenium (Se) is an essential nutrient for crustaceans. The dietary selenium requirement of juvenile oriental river prawn Macrobrachium nipponense was evaluated. Yeast-selenium was added to basal semi-purified diet at six levels to make diets with the concentration of 0.11, 0.31, 0.47, 0.59, 0.88 and 1.17mgSekg1. These diets were fed to juvenile prawns (initial weight 0.133±0.003g) in quintuplicate for 8weeks. Our results indicated that the growth performance of prawn was significantly affected by dietary selenium. Prawns fed the 0.47 and 0.59mgSekg1 diets achieved the highest weight gain rate (WGR), whereas the deficiency (0.11mgkg1) and excess (1.17mgkg1) of Selenium inhibited their growth. Whole-body and muscle Se concentrations generally increased with the level of dietary Se. The highest concentrations in body and muscle were observed in the prawns fed the 1.17mgkg1 diet, which were significantly higher than those of prawns using 0.11, 0.31, 0.47 and 0.59mgkg1 diets. Selenium also affects the activity of antioxidant enzymes. The activities of glutathione peroxidase (GSH-Px) and superoxide dismutase (SOD) were significantly higher in prawns fed with 0.31, 0.47 and 0.59mgSekg1 than other groups, whereas the maleic dialdehyde (MDA) content had the opposite pattern from GSH-Px activity. Significantly elevated glutathione reductase (GR) activity and reduced glutathione (GSH) content were found in prawns fed the 0.31, 0.47, 0.59 and 0.88mgkg1 diets. The prawns fed with 0.31–0.88mgSekg1 exhibited the highest total antioxidant competence (T-AOC activity), which was significantly higher than 1.17mgkg1 group. Furthermore, selenium is involved in prawn immune competence. Serum phenoloxidase (PO) and lysozyme activities in prawns fed the 0.31, 0.47, 0.59 and 0.88mgSekg1 diets were significantly higher than those fed the 0.11 and 1.17mgSekg1 diets. The minimum dietary selenium requirements for maximal growth and antioxidant ability of juvenile oriental river prawn were evaluated as 0.58–0.68mgkg1 diet based on WGR and GSH-Px activity in the hepatopancreas, and 1.07mgSekg1 diet was required to maximize whole body selenium content. Statement of relevance In this study, we evaluated the minimum dietary selenium requirement for juvenile oriental river prawn Macrobrachium nipponense. Dietary selenium deficiency and excess significantly reduced growth, antioxidant ability and immunity of prawn. Our results illustrate that supplementing appropriate amount of dietary selenium is necessary in prawn culturing. The minimum dietary selenium level for maximal growth and antioxidant ability of juvenile M. nipponense is recommended as 0.58–0.68mgkg1 diet based on the analyses of WGR and GSH-Px activity, and 1.07mgSekg1 diet is required to maximize whole body selenium content. This research will facilitate to the development of practical diet for prawn.





Combined replacement of fishmeal and fish oil in European sea bass (Dicentrarchus labrax): Production performance, tissue composition and liver morphology

Published on 29/4/2017
Publication date: 1 May 2017
Source:Aquaculture, Volume 474

Author(s): S. Torrecillas, L. Robaina, M.J. Caballero, D. Montero, G. Calandra, D. Mompel, V. Karalazos, S. Kaushik, M.S. Izquierdo

The aim of this study was to evaluate the combination of maximum replacement of fishmeal (FM) and fish oil (FO) by alternative meals (AM) and oils (AO) to develop nutritious, but more eco-friendly diets for European sea bass (Dicentrarchus labrax) juveniles. European sea bass of 9.8±1.5g and 9.1±0.5cm were fed nine isonitrogenous (45% crude protein) and isolipidic (21%) diets containing gradually reduced levels of FM and FO as follows (%FM/%FO): 58/15, 20/6, 20/3, 10/6, 10/3, 5/6, 5/3 and 0/0. Another diet, 0/0+, was similar to the 0/0 but supplemented with LC-PUFA from microbial and marine sources. After 90 days of feeding, European sea bass fed the 0/0 diet showed reduced (P<0.05) final weight, final length, condition factor, perivisceral fat index and viscero-somatic index as well as feed efficiency, whereas addition of LC-PUFA significantly improved daily growth index (DGI) (0/0+ diet). Reduction of FM/FO down to 5/3 did not significantly affect fish survival or condition factor, whereas reduction to 5/6 did neither affect sea bass length or feed conversion and reduction down to 10/3 did not affected body weight, DGI and perivisceral fat or visceral weight. FM reductions down to 5% significantly reduced growth rate. FO substitution by vegetable oils (VO) led to reduced growth and increased liver to body weight ratios, liver lipid deposition and hepatocellular size. In liver and muscle, FO substitution increased n-6 fatty acids (FA) and n-6/n-3 ratio and reduced saturated FA and n-3 LC-PUFA, whereas monounsaturated FA were not increased in proportion to dietary contents. Moreover, FO reduction increased the products from Δ6 desaturase and elongases, Elovl6 and Elovl5. In conclusion, the results of this study show that it is possible to reduce dietary FM and FO levels down to 10% and 3% in mostly plant-based diets without affecting growth performance of European sea bass juveniles.





Black soldier fly (Hermetia illucens) pre-pupae meal as a fish meal replacement in diets for European seabass (Dicentrarchus labrax)

Published on 29/4/2017
Publication date: 1 July 2017
Source:Aquaculture, Volume 476

Author(s): Rui Magalhães, Antonio Sánchez-López, Renato Silva Leal, Silvia Martínez-Llorens, Aires Oliva-Teles, Helena Peres

A feeding trial was carried out to assess the effect of partially replacing fish meal (FM) by Black soldier fly pre-pupae meal (HM) in diets for European seabass Dicentrarchus labrax juveniles. A FM-based diet was used as a control and three other diets were formulated to include 6.5%, 13%, and 19.5% of HM, replacing 15%, 30% and 45% of FM respectively. Each diet was fed to triplicate groups of fish (initial weight: 50g) for 62days. At the end of the trial, there were no differences among groups in growth performance or feed utilization. Plasma metabolic profiles also remained unaffected, except that plasma cholesterol was reduced with dietary HM inclusion. The apparent digestibility coefficients (ADC) of protein, lipids, dry matter, organic matter, and energy were generally high, and not affected by the dietary treatment. The ADC of arginine, histidine, and valine were higher in HM diets when compared to the control. Amylase and protease activities were not affected by dietary HM, while lipase activity was lower in HM 6.5 diets than in the control and HM 19.5 diets. In conclusion, up to 19.5% of HM, corresponding to 22.5% of total dietary protein, may successfully replace FM in diets for juvenile European seabass, without adverse effects on growth performance, feed utilization or digestibility.





Alternative prophylaxis/disinfection in aquaculture - Adaptable stress induced by peracetic acid at low concentration and its application strategy in RAS

Published on 29/4/2017
Publication date: 1 May 2017
Source:Aquaculture, Volume 474

Author(s): Dibo Liu, Lars-Flemming Pedersen, David L. Straus, Werner Kloas, Thomas Meinelt

The application of peracetic acid (PAA) at low concentrations has been proven to be a broad-functioning and eco-friendly prophylaxis/disinfection method against various fish pathogens. However, there is lack of knowledge on how to apply PAA in a recirculating aquaculture system (RAS), and whether the application of PAA at low concentration can affect fish welfare. In the present study, PAA was applied in a pilot-scale carp (Cyprinus carpio) RAS (comprised of a fish culture tank of 1m3, a reservoir tank of 600L and a filter complex of 400L) every 3 or 4days for 5weeks, and the stress response of fish was monitored during every second PAA application by measuring cortisol in water. Results showed that the increase of water cortisol became less pronounced and the decrease of water cortisol occurred earlier after repeated applications of PAA, which indicates an adaptation of the stress response to PAA in the carp. Moreover, the mathematic model showed that the equal distribution of PAA in RAS was a slow progress, which depended on tanks size and flow rate. To avoid potential harm to the biofilter in RAS during PAA application, it's suggested that PAA should be applied only to the fish culture tank at a reduced flow rate. Statement of relevance Fish welfare becomes more and more important in aquaculture. However, there is a lack of knowledge if routine prophylaxis/disinfectant might affect fish welfare. In the present study, we tested how fish responded to repeated applications of peracetic acid (PAA) in a pilot-scale recirculating aquaculture system (RAS) via measurement of cortisol in water. The results showed that fishes reduced their stress during subsequent PAA application, indicating adaptation of fish to repeated prophylaxis/disinfection with PAA. Moreover, we established a model and measured the PAA concentration onsite to investigate the distribution of PAA in RAS. We found out that by simply adding PAA only to the fish culture tank with a reduced flow rate can avoid the potential harm on the biofilter. Findings from the current study provide insights that may prove of benefit to future treatment based studies.





Optimal salinity for rearing Chinese black sleeper (Bostrychus sinensis) fry

Published on 29/4/2017
Publication date: 1 July 2017
Source:Aquaculture, Volume 476

Author(s): Yu Ting Zhang, Sheng Huang, Heng Tong Qiu, Zhe Li, Yong Mao, Wan Shu Hong, Shi Xi Chen

The Chinese black sleeper (Bostrychus sinensis) is a commercially important fish in southeastern China, but the effects of salinity on the growth of B. sinensis fry remain unclear. In the present study, the three month-old B. sinensis fry were reared for 5weeks at 5, 15, 25 and 35 parts per thousand (ppt) salinities to evaluate the effects of salinity on the survival rate, specific growth rate, condition factor, feed intake (FI), food conversion efficiency (FCE), plasma osmolality, plasma Cl concentration and the gill Na+-K+-ATPase (NAK) activities. In addition, since the insulin-like growth factor (IGF) system plays important roles in osmoregulation and promoting growth in teleosts, the complete B. sinensis insulin-like growth factor-1 receptor (igf-1r) gene was cloned and igf-1r mRNA levels in the muscle and gill were measured at the end of this experiment. Our results showed that the fry reared at lower salinities (5 and 15 ppt) grew significantly faster than those at higher salinities (25 and 35 ppt), and the fry reared at 15 ppt exhibited lower FI and higher FCE than those reared at 5 ppt. A typical ‘U-shaped’ pattern of gill NAK activity levels with the lowest one at 15 ppt was observed, suggesting that a lower energy expenditure on osmoregulation at this level of salinity. The length of the complete igf-1r cDNA sequence was 6864bp, and it had a wide range of tissue expression including muscle and gill. After 5weeks of rearing, muscle igf-1r mRNA levels were similar among the four salinity groups, while the gill igf-1r mRNA level at 5 ppt was significantly higher than that at 15 ppt. Taken together, the results from the present study indicated that the optimal salinity for rearing B. sinensis fry was 15 ppt, and that IGF-1 might serve as a hyperosmoregulatory hormone in long-term low salinity acclimation in B. sinensis.





Pollution potential indicators for feed-based fish and shrimp culture

Published on 29/4/2017
Publication date: Available online 28 April 2017
Source:Aquaculture

Author(s): Sirirat Chatvijitkul, Claude E. Boyd, D. Allen Davis, Aaron A. McNevin

The oxygen demand, acidification potential, and waste loads of carbon dioxide, nitrogen, and phosphorus from feed were determined for production of channel catfish Ictalurus punctatus, tilapia Oreochromis spp., Atlantic salmon Salmo salar, rainbow trout Oncorhynchus mykiss, and whiteleg shrimp Litopenaeus vannamei. Loads of these variables in culture systems (system loads) at typical FCRs ranged from 1090 to 1500kgt1 for feed oxygen demand, 270–440kgt1 for acidification potential, 1186–1885kgt1 for carbon dioxide, 35.9–63.5kgt1 for nitrogen, and 6.1–15.9kgt1 for phosphorus. Using these estimates as representative of feed-based aquaculture and literature data on the proportions of system waste loads typically discharged to the environment (environmental loads), the approximate amounts of waste generated globally by feed-based aquaculture were estimated to be small in comparison to estimates of global anthropogenic waste. Nevertheless, aquaculture should lessen its environmental waste load, and the benefit of improving FCR in reducing waste load was illustrated. Statement of relevance This research will be important in efforts to assess the pollution potential of aquaculture facilities. This will be especially important for aquaculture certification efforts.





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