Microalga <Emphasis Type="Italic">Isochrysis galbana</Emphasis> in feed for <Emphasis Type="Italic">Trachinotus ovatus</Emphasis>: effect on growth performance and fatty acid composition of fish fillet and liver

Seeking alternatives to the depleting fish oil are crucial for marine fish aquaculture, which is currently dependent on fish oil as the primary source of n-3 long-chain polyunsaturated fatty acids (n-3 LC-PUFAs). Five isonitrogenous (46% crude protein) and isolipidic (16% crude lipid) feed diets (FO, ISO2.9, ISO4.8, ISO6.7, ISO8.6) were formulated by partially replacing fish oil with microalgae Isochrysis galbana. These diets were fed to triplicate tanks of Trachinotus ovatus (mean initial weight 1.92 g) for 80 days. This work demonstrates that a moderate inclusion (around 4.5–5.0 wt%, equivalent to the replacement of 24–26 wt% fish oil) of I. galbana biomass in fish diet improves fish growth performance, lipid deposition and enhances total n-3 fatty acids, DHA, and EPA contents in neutral and polar lipids (PLs) of fish muscle and liver of T. ovatus. The results disclosed in this study suggest that I. galbana microalgae represents a potential high-quality substitute for fish-based ingredients in aquaculture feeds, which can be a promising sustainable solution to resolve the depleting fish oil resource in a cost-effective manner.     

Growth and fatty acid composition of <Emphasis Type="Italic">Octopus vulgaris</Emphasis> paralarvae fed with enriched <Emphasis Type="Italic">Artemia</Emphasis> or co-fed with an inert diet

The rearing of Octopus vulgaris paralarvae during its planktonic life stage is a major challenge, as mortality is currently very high and unpredictable. In this study, we examined the survival and growth rates, as well as the fatty acid composition, of O. vulgaris paralarvae fed on three different dietary treatments: group ArDHA was offered juvenile Artemia enriched with a lipid emulsion (Easy DHA-Selco^®); group ArMA was fed with juvenile Artemia enriched with a mixture of microalgae (Rhodomonas lens and Isochrysis galbana); and group ArMA+ID received the same Artemia as group ArMA complemented with an inert diet. Dietary treatments were tested in triplicate with homogenous groups of paralarvae (25 individuals l^?1) established in 50-l tanks, and the experiment was conducted for 15 days. The survival rate of 15-day post-hatch (-dph) paralarvae from groups ArMA (20 ± 8%) and ArMA+ID (17 ± 4%) tended to be higher than in group ArDHA (13 ± 5%), though these differences were not statistically different. The dry weight (DW) of 15-dph paralarvae increased by almost 60% in groups ArMA and ArMA+ID, and nearly 40% in group ArDHA, with respect to hatchlings. The fatty acid (FA) composition of paralarvae revealed a remarkable drop of docosahexaenoic acid (22:6n-3, DHA) from hatchlings to 15-dph paralarvae of all groups (P < 0.05). However, paralarvae from group ArDHA contained higher levels of DHA than those from ArMA and ArMA+ID (P < 0.05). Despite Artemia enriched with DHA-Selco^® contained three-times more DHA than Artemia enriched with microalgae, no beneficial effects of this dietary treatment were observed on the performance of paralarvae.     

Evaluation of different <Emphasis Type="Italic">Pyropia yezoensis</Emphasis> extracts as feed additives for growth and immunity of Japanese flounder <Emphasis Type="Italic">Paralichthys olivaceus</Emphasis>

We evaluated the effects of diets incorporating the red algae Pyropia yezoensis, prepared by several different extraction methods, on the growth of juvenile Japanese flounder Paralichthys olivaceus. We assessed growth performance, as well as the levels of amino acids, fatty acids, insulin-like growth factor I (IGF-I) and interleukins (ILs). Four experimental diets were developed based on different methods of processing P. yezoensis. A commercial feed, laver powder (P), high-pressure heat extraction of laver (HPHE) and acid hydrolysis extraction of laver were used as the experimental diets. Three experimental replicates were established for each diet (40 fish/group, body weight 123.7 ± 1.1 g), and the fish were fed for 6 weeks. We found no significant differences in weight gain, specific growth rate or feeding efficiency among the groups (P > 0.05); however, the fish fed HPHE had the greatest growth performance. Fish fed the laver extracts exhibited the highest protein efficiency ratio compared with the control and P groups. The experimental groups fed P. yezoensis extracts had significantly higher levels of IGF-I (P < 0.05) than those of the control group. High levels of IL-2 were found in the P and HPHE groups, IL-12 in the HPHE group, and IL-6 in all experimental groups. Therefore, these results suggest that a P. yezoensis extract improved the growth performance and immunity of Japanese flounder. In particular, the high-pressure heating process was a useful extraction method for preparing a P. yezoensis extract, which had beneficial effects as a dietary supplement in Japanese flounder.     

Influence of different microalgal diets on gonadal development of the carpet shell clam <Emphasis Type="Italic">Ruditapes decussatus</Emphasis> broodstock

Studies considering broodstock conditioning of Ruditapes decussatus mostly used flagellates and diatoms for feeding, mainly Isochrysis galbana and Chaetoceros calcitrans, respectively. The present study evaluated the effect of different microalgal diets on gonadic maturation of R. decussatus including three microalgae species (C. calcitrans, Tetraselmis suecica, and Nannochloropsis oculata) which were used to prepare six diets: three monospecific and three bispecific mixed diets at a proportion of 1:1. Clams were daily fed at a ratio of 1% dry weight of algae/live weight of clam and unfed treatment was used as control. Results showed that clams fed C. calcitrans alone or mixed with T. suecica attained earlier full maturity with the highest response to spawning induction (after 34 conditioning days) and largest proportion in the partial spawning phase for both, followed by T. suecica alone after 48 days. In contrast, N. oculata alone or mixed diets demonstrated poor performance for gonadal maturation. Unfed treatment did not show any sign of maturation. The results indicated that T. suecica has high conditioning potential like C. calcitrans and their mixture gave the highest benefit. Therefore, T. suecica can be recommended for R. decussatus broodstock conditioning.     

Alternative microalgal diets for cultivation of the fairy shrimp <Emphasis Type="Italic">Branchinella thailandensis</Emphasis> (Branchiopoda: Anostraca)

Fairy shrimp is known as a nutritional food for fish and crustaceans in aquaculture. In most hatcheries, the microalga Chlorella sp. appears to be the most common, suitable, and nutritious food to feed fairy shrimp. In this study, we attempted to determine other alternative algal diets for cultivation of fairy shrimp Branchinella thailandensis. Seven experimental diets including three treatments of dried Spirulina sp. at 0.75 (S1), 1.5 (S2), and 3.0 mg dry weight individual^?1 (S3); three treatments of Chlorococcum humicola at 5 × 10⁵ (Ch1), 1 × 10⁶ (Ch2), and 2 × 10⁶ cells mL^?1 (Ch3); and a control diet (Chlorella vulgaris at 1 × 10⁶ cells mL^?1) were fed to 5-day-old shrimp for 15 days. Evaluation of growth performance, egg production, survival percentage, and nutritional and carotenoid content of the experimental fairy shrimp revealed that Ch3 is the most suitable algal diet. Our results suggest that C. humicola is the best alternative food source for the cultivation of B. thailandensis. In addition, dried Spirulina powder is also a good choice when live algae are not available and can be used as an alternative feed in fairy shrimp cultures.     

Comparative nutritional value of <Emphasis Type="Italic">Jatropha curcas</Emphasis> protein isolate and soy protein isolate in common carp

Jatropha seed cake (JSC) is an excellent source of protein but does contain some antinutritional factors (ANF) that can act as toxins and thus negatively affect the growth and health status of fish. While this can limit the use of JSC, detoxified Jatropha protein isolate (DJPI) may be a better option. An 8-week study was performed to evaluate dietary DJPI to common carp Cyprinus carpio. Five iso-nitrogenous diets (crude protein of 38%) were formulated that consisted of a C _ontrol (fish meal (FM) based protein), J ₅₀ or J ₇₅ (50 and 75% of FM protein replaced by DJPI), and S ₅₀ or S ₇₅ (50 and 75% of FM protein replaced by soy protein isolate, SPI) and fed to triplicate groups of 75 carp fingerlings (75; av. wt. ± SD; 11.4 ± 0.25 g). The growth, feeding efficiencies, digestibility, plasma biochemistry, and intestinal enzymes were measured. Results showed that growth performance of fish fed the S ₇₅- or DJPI-based diets were not significantly different from those fed the C _ontrol diet, while carp fed the S ₅₀ had significantly better growth than the J ₇₅ diet. Fish fed the J ₇₅ diet had significantly lower protein and lipid digestibility as well as significantly lower intestinal amylase and protease activities than all other groups. However, all plant protein-based diets led to significantly higher crude protein, crude lipid, and gross energy in the body of common carp compared to the control treatment. Plasma cholesterol and creatinine significantly decreased in the plant protein fed groups, although plasma triglyceride as well as the red blood cells count, hematocrit, albumin, globulin, total plasma protein, and lysozyme activity were higher in plant protein fed groups compared to FM fed group. White blood cells, hemoglobulin concentration, alkaline phosphatase and alanine transaminase activities, and glucose level in blood did not differ significantly among treatments. The results suggest that the DJPI is non-toxic to carp and can be used to replace FM in the diets of common carp up to 75%, but further research to potentially reduce some inherent ANF within this protein source, such as non-starch polysaccharides, may improve nutrient utilization.     

Growth performance,body composition,and digestive functionality of Senegalese sole (<Emphasis Type="Italic">Solea senegalensis</Emphasis> Kaup, 1858) juveniles fed diets including microalgae freeze-dried biomass

Senegalese sole is one of the most promising fish species cultivated in the Southern European countries. This study was aimed at assessing the effects of microalgae biomass added to diets for Senegalese sole juveniles on fish growing and condition status. Three isoproteic (52%) and isolipidic (10%) were formulated containing 15% Tisochrysis lutea (TISO), Nannochloropsis gaditana (NAN), or Scenedesmus almeriensis (SCE) biomass, respectively. An experimental microalgae-free diet (CT) and a commercial diet (COM) were used as controls. Fish were fed at 3% of their body weight for 85 days. Final body weight of fish fed microalgae-supplemented diets did not differ from group fed CT diet. Fish-fed CT, TISO, NAN, and SCE showed higher growth performance and nutrient utilization figures than specimen-fed COM diet. The highest carcass lipid content was found in COM group (141 g kg^?1), and no differences were observed in body protein content. Ash was significantly higher in TISO, NAN, and SCE groups compared to fish-fed CT. Muscle EPA and DHA contents were not modified owing to the different dietary treatments. The n3/n6 and EPA/DHA ratios in muscle were similar in all the experimental groups. The quantification of digestive proteolytic activities did not differ among experimental groups, although differences in the protease pattern in digestive extracts by zymography were revealed in those fish fed on COM diet. Both α-amylase activity in the intestinal lumen and leucine aminopeptidase in the intestinal tissue were significantly lower in COM fish. Specimens fed on SCE diet showed a higher leucine aminopeptidase activity associated to the intestinal tissue compared to NAN-fed fish (0.40 and 0.25 U g tissue^?1, respectively). The ultrastructural study revealed that the dietary inclusion of algal biomass, especially T. lutea and N. gaditana, had a positive impact on the absorptive capacity of the intestinal mucosa. The highest values for the parameters microvilli length and microvilli absorption surface were observed in fish fed on NAN diet (1.99 μm and 45.93 μm², respectively). Even though further studies aimed at optimizing commercial formulas for Senegalese sole are required prior to any large-scale practical utilization, the results obtained clearly suggest the potential of microalgae as dietary ingredients for this fish species.     

Hepatic RNA:DNA ratio as a reliable indicator of the growth performance of juvenile <Emphasis Type="Italic">Pelodiscus sinensis</Emphasis> under nutritional stress

We investigated the reliability of the ratio of RNA to DNA in juvenile Pelodiscus sinensis under moderate nutritional stress from lack of sufficient protein. The control diet contained 45% protein. Two experimental diets containing 40 and 35% protein were used to trigger nutritional stress. One hundred fifty-six turtles were randomly divided into the three diet groups and fed for 90 days. Four turtles were randomly sampled from each group on days 2, 4, 7, 15, 30, 45, 60, 75 and 90 of the trial and their hepatic RNA:DNA was measured. Each turtle was weighed on days 15, 30, 45, 60, 75 and 90. Obvious positive correlations between RNA:DNA and specific growth rate (SGR) were found, which were affected by dietary protein levels. The exponential regression model of the relationship between RNA:DNA (x) and SGR (y) in turtles fed 45% protein diet was y = 0.8001e^0.3072x , in the 40% protein diet it was y = 0.5374e^0.4297x , and in the 35% protein diet it was y = 0.7867e^0.369x . From day 7 until the end of the trial, RNA:DNA accurately distinguished differences among the three groups. We suggest that hepatic RNA:DNA is a sensitive and quick indicator of growth performance in juvenile turtles, especially in studies related to nutritional stress.     

Growth performance and immune responses of gibel carp, <Emphasis Type="Italic">Carassius auratus gibelio</Emphasis>, fed with graded level of rare earth-chitosan chelate

A 12-week feeding trail was conducted to assess the effect of rare earth-chitosan chelate (RECC) on growth performance and immune responses of gibel carp, Carassius auratus gibelio. Isonitrogenous and isolipid experimental diets were supplemented with graded levels of rare earth-chitosan chelate (RECC 0, 0.8, 4 and 8 g Kg^?1). A total of 720 gibel carps (initial body weight about 14.32 g) were divided randomly into four groups with six replicates, respectively. Fish were fed with the experimental diets three times every day. At the end of the feeding trail, the survival rate was higher than 96 %. Weight gain rate and specific growth rate (SGR) significantly increased with RECC supplementation up to 0.8 g Kg^?1 (P < 0.05) and tended to decline at higher supplementation levels, while feed conversion ratio was not significantly different between groups (P > 0.05). Based on broken-line regression analysis of SGR, the optimum dietary RECC was estimated to be 0.71 g Kg^?1 of the diet. Condition factor and viscerosomatic index were not significantly affected by RECC (P > 0.05), while hepatosomatic index in the group fed with 0.8 g Kg^?1 RECC (3.45 ± 0.10 %) was significantly lower than in other groups (P < 0.05). Plasma ALT was significantly affected by RECC (P < 0.05), while AST was not. Plasma total protein and albumin were increased with RECC supplementation up to 0.8 g Kg^?1 and decreased significantly at higher supplementation levels (P < 0.05). RECC supplementation significantly decreased plasma urea and glucose concentration and increased plasma creatinine concentration significantly (P < 0.05). Respiratory burst activity of phagocytes and myeloperoxidase activity were not significantly different between groups, while superoxide dismutase activity and nitrogen monoxide concentration were increased with the increasing level of RECC in the diets. In conclusion, RECC could enhance growth performance and improve immunity of gibel carp.     

<Superscript>1</Superscript>H-NMR metabolite profiling of abalone digestive gland in response to short-term starvation

The effect of a short-term feeding and starvation experiment on juvenile abalone (Haliotis rubra × H. laevigata) was investigated (average length = 67 mm; average weight = 48 g). All aquaculture experiments were conducted at The University of Melbourne, Australia. Artificial feed was supplied ad libitum to the fed group, and no feed was supplied to the starved group. A modified metabolite extraction protocol using deuterated solvents was developed for ¹H-NMR-based metabolite profiling of digestive gland in response to the short-term feeding/starvation experiment, to avoid lyophilisation prior to biochemical analysis. PLS-DA revealed that fed and starved abalone are metabolically distinct from each other after 28 and 56 days. After 28 days, the fed group was defined by an increase in arginine, glucose, glutamate, glycine, inosine and uracil (P < 0.05), and the starved group was defined by an increase in N,N-dimethylglycine. After 56 days, the fed group still displayed increased glucose (P < 0.05), while N,N-dimethylglycine remained elevated in the starved group (P < 0.05). Arginine and glycogen were all higher at 28 days compared to 56 days, suggesting decreased anaerobic energy production at the later time point. Only glucose and N,N-dimethylglycine were significantly different between the fed and starved groups after 56 days, suggesting that abalone had not acclimatised to the starvation treatment after 28 days. These results infer N,N-dimethylglycine is a robust marker for short-term starvation in abalone. ¹H-NMR was also conducted on the artificial feed and starved abalone faecal matter, revealing the biochemical differences between them and digestive gland tissue. These methodology and results will facilitate a deeper understanding of the nutritional and physiological requirements of abalone in an aquaculture setting.     

Dietary supplementation of curcumin augments heat stress tolerance through upregulation of <Emphasis Type="Italic">nrf-2</Emphasis>-mediated antioxidative enzymes and <Emphasis Type="Italic">hsps</Emphasis> in <Emphasis Type="Italic">Puntius sophore</Emphasis>

Heat stress is one of the major environmental concerns in global warming regime and rising temperature has resulted in mass mortalities of animals including fishes. Therefore, strategies for high temperature stress tolerance and ameliorating the effects of heat stress are being looked for. In an earlier study, we reported that Nrf-2 (nuclear factor E2-related factor 2) mediated upregulation of antioxidative enzymes and heat shock proteins (Hsps) provide survivability to fish under heat stress. In this study, we have evaluated the ameliorative potential of dietary curcumin, a potential Nrf-2 inducer in heat stressed cyprinid Puntius sophore. Fishes were fed with diet supplemented with 0.5, 1.0, and 1.5% curcumin at the rate 2% of body weight daily in three separate groups (n = 40 in each group) for 60 days. Fishes fed with basal diet (without curcumin) served as the control (n = 40). Critical thermal maxima (CTmax) was determined for all the groups (n = 10, in duplicates) after the feeding trial. Significant increase in the CTmax was observed in the group fed with 1.5% curcumin- supplemented fishes whereas it remained similar in groups fed with 0.5%, and 1% curcumin-supplemented diet, as compared to control. To understand the molecular mechanism of elevated thermotolerance in the 1.5% curcumin supplemented group, fishes were given a sub-lethal heat shock treatment (36 °C) for 6 h and expression analysis of nrf-2, keap-1, sod, catalase, gpx, and hsp27, hsp60, hsp70, hsp90, and hsp110 was carried out using RT-PCR. In the gill, expression of nrf-2, sod, catalase, gpx, and hsp60, hsp70, hsp90, and hsp110 was found to be elevated in the 1.5% curcumin-fed heat-shocked group compared to control and the basal diet-fed, heat-shocked fishes. Similarly, in the liver, upregulation in expression of nrf-2, sod, catalase, and hsp70 and hsp110 was observed in 1.5% curcumin supplemented and heat shocked group. Thus, this study showed that supplementation of curcumin augments tolerance to high temperature stress in P. sophore that could be attributed to nrf-2-induced upregulation of antioxidative enzymes sod, catalase, gpx, and the hsps.     

Effects of the supplementation of vitamin D<Subscript>3</Subscript> on the growth and vitamin D metabolites in juvenile Siberian sturgeon (<Emphasis Type="Italic">Acipenser baerii</Emphasis>)

The objective of this study was to evaluate the effects of the supplementation of vitamin D₃ on the growth, vitamin D metabolites, and osteocalcin secretion in juvenile Siberian sturgeon (Acipenser baerii). A 90-day growth trial was conducted with juvenile Siberian sturgeon (initial body weight 3.47 ± 0.14 g) fed seven isonitrogenous and isoenergetic practical diets (45% CP and 13% lipid) containing 60 (basal diet), 240, 450, 880, 1670, 3300, or 1.0 × 10⁵ IU/kg feed (D60~D 1.0 × 10⁵) vitamin D₃. The results showed that weight gain and specific growth rate increased as the dietary vitamin D₃ levels increased from 450 to 3300 IU/kg (P < 0.05). The fish fed with D1670 and D3300 diets had higher crude lipid and ash levels than the fish fed the D60 diet (P < 0.05). The fish fed D880, D1670, or D3300 diets had higher 25-OH-D₃ and 1,25-(OH)₂-D₃ levels than the fish fed the D60 diet (P < 0.05). The fish fed D880, D1670, D3300, or D1.0 × 10⁵ diets had higher osteocalcin levels than the fish fed the D60 diet (P < 0.05). Based on the broken line method analysis of weight gain and osteocalcin, the dietary vitamin D₃ requirement of juvenile Siberian sturgeon was estimated to be 1683.30 and 1403.27 IU/kg per diet, respectively.     

Physiological response,blood chemistry profile and mucus secretion of red sea bream (<Emphasis Type="Italic">Pagrus major</Emphasis>) fed diets supplemented with <Emphasis Type="Italic">Lactobacillus rhamnosus</Emphasis> under low salinity stress

Environmental stressors caused by inadequate aquaculture management strategies suppress the immune response of fish and make them more susceptible to diseases. Therefore, efforts have been made to relieve stress in fish by using various functional feed additives in the diet, including probiotics. The present work evaluates the effects of Lactobacillus rhamnosus (LR) on physiological stress response, blood chemistry and mucus secretion of red sea bream (Pagrus major) under low salinity stress. Fish were fed four diets supplemented with LR at [0 (LR0), 1 × 10² (LR1), 1 × 10⁴ (LR2) and 1 × 10⁶ (LR3) cells g^?1] for 56 days. Before stress, blood cortisol, urea nitrogen (BUN) and total bilirubin (T-BIL) showed no significant difference (P > 0.05), whereas plasma glucose and triglyceride (TG) of fish-fed LR2 and LR3 diets were significantly lower (P < 0.05) than those of the other groups. Plasma total cholesterol (T-CHO) of fish-fed LR3 diet was significantly (P < 0.05) lower than that of the other groups. Furthermore, total plasma protein, mucus myeloperoxidase activity and the amount of mucus secretion were significantly enhanced in LR-supplemented groups when compared with the control group (P < 0.05). After the application of the low salinity stress test, plasma cortisol, glucose, T-CHO and TG contents in all groups showed an increased trend significantly (P < 0.01) compared to the fish before the stress challenge. However, plasma total protein and the amount of secreted mucus showed a decreased trend in all groups. On the other hand, BUN, T-BIL and mucus myeloperoxidase activity showed no significant difference after exposure to the low salinity stress (P > 0.05). In addition, the fish that received LR-supplemented diets showed significantly higher tolerance against low salinity stress than the fish-fed LR-free diet (P < 0.05). The physiological status and the detected immune responses, including total plasma protein and mucus myeloperoxidase activity in red sea bream, will provide a more comprehensive outlook of the effects of probiotics to relieve stress in fish.     

Complete replacement of fish meal by other animal protein sources on growth performance of <Emphasis Type="Italic">Clarias gariepinus</Emphasis> fingerlings

To completely replace the fish meal by a mixture of earthworm and maggot meals, experimental diets were tested during 42 days on Clarias gariepinus fingerlings. Five isoproteic and isoenergetic diets (40 % crude protein and 17.9 ± 0.3 kJ g^?1) including the control diet (D1) based on fish meal, were formulated. All these diets satisfied the essential amino acids requirements of C. gariepinus fingerlings. These diets were tested on triplicate groups of 50 fishes (initial body weight: 3 ± 0.1 g) bred in tank (0.5 m³). The approximate ratios 2:5; 1:4; 1:12 and 0:1 between the earthworm meal and the maggot meal were used, respectively, to formulate four diets D2, D3, D4 and D5 without fish meal. After the feeding period, significant differences (P < 0.05) were observed on growth, feed utilization between control diet (D1) and test diets (D2–D5). Fish fed earthworm- and maggot-based diets were grown better than those fed the control diet. Survival and feed utilization were not significantly affected by the ratio between earthworm meal and maggot meal in the test diets. Lipid content was higher in carcass and fillet of fishes fed earthworm- and maggot meals-based diets than that of those fed fish meal-based diet. This study indicates that when the ratio 2:5 between the earthworm meal and the maggot meal is used to entirely replace fish meal and the ratio lysine/arginine of the diet is inferior to 1, the growth performances and feed utilization of Clarias gariepinus fingerlings are improved.     

Modulation of appetite,lipid and glucose metabolism of juvenile grass carp (<Emphasis Type="Italic">Ctenopharyngodon idellus</Emphasis>) by different dietary protein levels

This study was undertaken to explore the systemic metabolic strategies of juvenile grass carp (Ctenopharyngodon idellus) to maintain growth when fed with different dietary protein levels. The optimal growth group and two growing discomfort groups were selected through the basic data, to explain the growth difference from appetite regulation and lipid and glucose metabolism perspective. Three experimental diets were formulated with three dietary protein levels at 200.3, 296.1 and 442.9 g kg^?1, named P1, P2 and P3, respectively. Juvenile grass carp (initial body weight 12.28 ± 0.14 g) were fed with three diets with 3 replications per dietary treatment in an indoor recirculation system for an 8-week feeding trial. Fish fed with diet P2 dietary group showed significantly higher WG, SGR, FI and PER than other groups. Compared with other groups, mRNA expressions of NPY, Y8a and Y8b in fish fed with P2 significantly down-regulated, while the expressions of CCK and CART in fish fed with P3 significantly down-regulated (P < 0.05). With increasing dietary protein levels, G6Pase, GK, PK and PEPCK were all significantly inhibited (P < 0.05). For lipid metabolism, the mRNA expression of ACC in P1 dietary group was significantly higher than P3 dietary group; besides, LPL expression in P3 group was significantly higher than other two groups (P < 0.05). PPARα expression in P2 was significantly lower than other groups (P < 0.05). These results suggested that grass carp fed with P2 (296.1 g kg^?1 protein level) showed highest weight gain, contributed to more balanced nutrient metabolism and appetite regulation. Too high dietary protein (442.9 g kg^?1) should be avoided because it induced lowest PER, body lipid and liver lipid, and inhibited glucose and lipid metabolism in juvenile grass carp.     

Effects of exogenous non-starch polysaccharide-degrading enzymes in diets containing <Emphasis Type="Italic">Gracilaria lemaneiformis</Emphasis> on white-spotted snapper <Emphasis Type="Italic">Lutjanus stellatus</Emphasis> Akazaki

A feeding experiment was conducted to investigate the effects of exogenous non-starch polysaccharide (NSP)-degrading enzymes in diets containing Gracilaria lemaneiformis (GL) on growth performance and digestive enzyme activities of white-spotted snapper Lutjanus stellatus Akazaki (initial mass 8.0 ± 0.1 g). A basal diet (D0) containing a mixed protein source (fish meal, soybean meal and GL meal) was used as the control. Two diets supplemented with 0.5 g (D1) and 1 g (D2) exogenous NSP-degrading enzymes per kilogram of diet were formulated. Each diet was assigned to triplicate groups of fish in a total of nine floating sea cages (270 fish, 30 fish per cage). After a 60-day feeding trail, significantly higher weight gain, specific growth ratio and feed efficiency ratio were observed in fish fed D2 diet compared to those of control (P < 0.05). Body lipid, moisture and ash contents were not significantly affected by NSP-degrading enzyme supplementation, but significantly higher protein content was noticed in fish fed D2 diet compared to that of control (P < 0.05). The amylase activity in the stomach and intestine was significantly higher in fish fed D2 diet (P < 0.05), but no significant differences were observed in pepsin and lipase activities in the stomach or trypsin and lipase activities in the intestine between all treatments. The results suggested that addition of 1 g kg^?1 NSP-degrading enzymes in diet could efficiently improve seaweed feed utilization and growth performance of white-spotted snapper fish.     

Influence of the dietary inclusion of <Emphasis Type="Italic">Gracilaria cornea</Emphasis> and <Emphasis Type="Italic">Ulva rigida</Emphasis> on the biodiversity of the intestinal microbiota of <Emphasis Type="Italic">Sparus aurata</Emphasis> juveniles

Partial substitutions of fish meal by 5, 15, or 25 % of Gracilaria cornea or Ulva rigida in experimental diets were evaluated to study their effects on biodiversity of intestinal microbiota composition in gilthead seabream (Sparus aurata) juveniles. The diets were offered to duplicate groups of 15 juvenile fish (14.0 ± 0.5 g) for 70 days, and at the end of the experiment the intestinal microbiota from four specimens of each treatment was analysed by denaturing gel gradient electrophoresis. Results showed that the substitution of fish meal by algae meal induced important modifications in the intestinal microbiota community, as a big reduction of the biodiversity when the highest percentage (25 %) of U. rigida was included. On the contrary, an increase on the number of species was detected when a 15 % of algae was included. Various Lactobacillus delbrueckii subspecies were selectively stimulated when G. cornea was included in the feed, and other bacterial species, such as those included in the Vibrio genus, were reduced.     

Effects of starvation and feeding on blood chemistry,fatty acid composition and expression of vitellogenin and fatty acid-binding protein genes in female swimming crab <Emphasis Type="Italic">Portunus trituberculatus</Emphasis> broodstock

Portunus trituberculatus broodstock were stocked in plastic tanks to evaluate the effects of starvation and feeding on gonadal development, blood chemistry, fatty acid composition, and expression of vitellogenin (Vtg) and fatty acid-binding protein genes (FABP) in females. Two treatments (starved and fed) were randomly assigned to triplicate groups of 90 swimming crab broodstock (approximately 230 ± 45 g). In the starved treatment, crabs were starved for 30 days, whereas in the fed treatment crabs were fed once a day with clams. The gonadosomatic index decreased significantly in starved crabs (P < 0.05), as did the serum glucose and cholesterol concentrations; conversely, the total protein concentration in serum significantly increased (P < 0.05). In the ovary, there was a significant relative decline of 18:0, 16:1n-7 and 20:1n-9 fatty acids and relative increases of 20:4n-6, 22:6n-3, 18:1n-9 and 20:5n-3 in starved crabs compared to fed crabs (P < 0.05). Relative expression of Vtg in the ovary decreased significantly in starved crabs (P < 0.05), while there was no significant difference in hepatopancreas Vtg expression between starved and fed crabs (P > 0.05). Starvation suppressed gonadal development in female swimming crab broodstock.     

Inclusion of <Emphasis Type="Italic">Pediococcus acidilactici</Emphasis> as probiotic candidate in diets for beluga (<Emphasis Type="Italic">Huso huso</Emphasis>) modifies biochemical parameters and improves immune functions

Administration of probiotic candidates in fish has generally been shown as a useful strategy to improve growth performance, survival, digestive enzyme activity, and gut microbiota. Unfortunately, the sero-immunological responses of different fish to different probiotic candidates are poorly understood. The present study assessed the effect of Pediococcus acidilactici as a probiotic on the biochemical and immunological parameters of beluga. Fish (248.32?±?10.21 g) were fed a control diet (without P. acidilactici( and three different doses of P. acidilactici-supplemented diets (10⁷, 10⁸, and 10⁹ CFUg^?1 diets) for 8 weeks. On week 8, blood and serum were sampled. Dose-dependent increase of immunological parameters (respiratory burst activity, lysozyme content, serum antibacterial activity, and total immunoglobulin) and biochemical parameters (total protein and albumin levels) was observed. However, alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were significantly increased in the juvenile beluga fed by 10⁹ CFUg^?1 P. acidilactici-supplemented diet compared to the other groups. Based on the results of this evaluation, it is reasonable to conclude that the inclusion of P. acidilactici as probiotic in diets for juvenile beluga improves the sero-immunological parameters of the fish and should be considered by farmers as a strategy to improve fish health.     

Dietary supplementation of yeast (<Emphasis Type="Italic">Saccharomyces cerevisiae</Emphasis>) improves growth,stress tolerance,and disease resistance in juvenile Nile tilapia (<Emphasis Type="Italic">Oreochromis niloticus</Emphasis>)

The yeast Saccharomyces cerevisiae is one of the commonest probiotics incorporated in aquafeeds. An 84-day feeding trial was conducted to evaluate the effects of varying dietary inclusions of S. cerevisiae, 0% (control), 3% (YF3), 5% (YF5), and 7% (YF7), on growth, stress tolerance, and disease resistance in juvenile (body mass ~?21 g) Nile tilapia (Oreochromis niloticus). Fish were randomly distributed in groups of 20 into 12 1-m³ hapas and fed isoenergetic (~?17 kJ g^?1 gross energy) and isonitrogenous (~?300 g kg^?1 crude protein) diets at 3% of their bulk weight daily. Specific growth rates were significantly higher for the yeast-fed fish (0.77–0.78% day^?1) than for the control fish (0.60% day^?1) and resulted in significantly higher mean final weights for the yeast-treated groups. Protein and lipid retention efficiencies were also significantly higher in the yeast-fed fish than in the control group. In subsequent stress challenge trials, the yeast-fed fish had greater tolerance to acute heat as well as hypoxia exposure than the control fish. Survival rates of the yeast-treated groups following sudden exposure to elevated water temperature (40 °C) ranged from 82.5 to 100% compared to 15% for the control. Mean survival rates following a 24-h hypoxia exposure were also generally significantly higher for the yeast-fed fish. The probiotic groups recorded a relative percent survival (RPS) of 75% after a 14-day Aeromonas hydrophila infection challenge. The results of this study indicate that S. cerevisiae as an additive in Nile tilapia diets has beneficial impacts on growth, stress tolerance, and disease resistance.