Juvenile Golden Pompano Trachinotus Ovatus Research Articles

Effect of replacement of fishmeal by soybean products with attractants supplementation on the growth performance, feed utilization, body composition, plasma physiological responses and hepatic antioxidant abilities of juvenile golden pompano Trachinotus ovatus

A feeding experiment was carried out to develop a practical diet with low fishmeal for juvenile golden pompano (Trachinotus ovatus) by substituting fishmeal protein with soybean products mixture. Six isocaloric (17.6 KJ g−1) diets were designed by replacing 0 (FM100), 5 (FM95), 10 (FM90), 15 (FM85), 20 (FM80), and 25% (FM75) of the fishmeal with soybean products mixture (SPM) (soybean meal and soybean protein concentrate). The experiment diets were supplemented with 1.5%, 3%, 4.5%, 6% and 7.5% squid paste as attractants or palatability enhancer. The experimental fish (6.9 g) were cultured in sea cages (1.0 m × 1.0 m × 1.5 m) with 25 fish in each cage. Fish were fed the corresponding experimental diets to satiation twice daily for 8 weeks. At the end of the feeding experiment, no differences were found in the final weight and weight gain (WG) of fish fed FM100, FM85, FM80, and FM75 diets (P > 0.05). The WG was significantly (P < 0.05) better in the fish-fed FM95 diet compared to FM100 and FM75 diets. FCR in diet FM95 and FM90 was significantly (P < 0.05) than that of FM80 and FM75, but these values were not significantly different from those in other treatments. Although the condition factor value in diets FM90, FM85, and FM80 was significantly (P < 0.05) higher than that of FM100, these values were not significantly different from the rest of the other groups. There was no statistical difference in SGR, FR, VSI, and survival rates among different dietary treatments. The plasma AST activity was significantly lower in fish fed FM90 diet compared to fish fed with control, FM85, FM80, and FM75 (P < 0.05). There was no significant difference in plasma AST among all dietary treatments except FM95 and FM90. In contrast, the plasma AKP activity showed the opposite trend. Compared with the control, the fish-fed FM80 and FM75 diets had significantly decreased plasma cholesterol, triglyceride total protein, albumin, and globulin level (P < 0.05) while significantly increasing plasma COR levels (P < 0.05). There was no significant difference in ALT, Urea and glucose values among all treatments. No statistical difference was observed among the FM100, FM80, and FM75 treatments for those of plasma LYZ activity, C3, and C4 levels. The hepatic T-AOC and SOD activities were significantly increased in fish fed the FM90 diet (P < 0.05) compared to those in fish fed with FM100 diet. According to the current experiment, it can be concluded that SPM supplemented with SP could partially substitute fishmeal (25%) for juvenile golden pompano without any adverse symptoms.

Corn-starch based formulated diet has growth and feed utilization efficiency advantages over trash fish diet for juvenile golden pompano Trachinotus ovatus

Until now, trash fish/low valued fish continues to be widely used in marine cage culture of pompano and many other carnivorous species in China and other Asian countries. This study is the first attempt to compare the performance of juvenile golden pompano Trachinotus ovatus fed trash fish or starch-based formulated diets. Three isonitrogenous (41 %) and isolipidic (11 %) diets containing 16, 22 or 28 % corn starch were prepared. Juvenile pompano (mean initial weight: 28.0 ± 0.3 g) were fed either formulated diets or trash fish on a equivalent dry-matter basis for 8 weeks. The survival rates were significantly higher in fish fed starch diets than fish fed trash fish (P < 0.05). Specific growth rate (SGR) of fish fed the 22 % and 28 % starch diets was significantly higher than fish fed 16 % starch diet and trash fish. Feed intake (FI) of fish fed trash fish was significantly higher than those fed formulated diets; however, feed efficiency (FE) and protein efficiency ratio (PER) of fish fed the formulated diets were higher than those fed trash fish, with the 22 % starch dietary group having a significantly higher FE value than fish fed trash fish. The whole-body energy retention (ER) of fish fed the diet containing 22 % starch had the highest ER, significantly higher than those fed 16 % starch and trash fish. The moisture in whole-body tissues of fish fed trash fish was significantly higher than the formulated dietary groups. On the other hand, whole-body protein and lipid contents of fish fed the 22 % starch diet was significantly higher than the other dietary treatments. The whole-body lipid level of fish fed trash fish was significantly lower than the other dietary groups. The body condition indices were significantly higher for fish fed formulated diets compared to those fed trash fish. The viscerosomatic index (VSI) was decreased with increasing dietary starch levels. Hexokinase (HK) activity significantly increased with increasing dietary starch levels, whereas pyruvate kinase (PK) activity had an opposite trend. The liver and muscle glycogen contents were generally increased with increasing dietary starch levels. In addition, the intestinal microbial communities of fish fed the formulated diets and trash fish was distinctly different. The results shown that formulated diet had advantages in performance and feed utilization efficiency over trash fish. Corn starch can be used as a suitable dietary carbohydrate. Evaluated on growth and FE, the optimal dietary corn starch level for T. ovatus is 22–24 % of diet.

Beneficial contribution of the microalga Odontella aurita to the growth, immune response, antioxidant capacity, and hepatic health of juvenile golden pompano (Trachinotus ovatus)

Under specific culture conditions, the marine diatom Odontella aurita can accumulate chrysolaminarin, which has antioxidant and anti-inflammatory functions, to improve immunity and regulating lipid metabolism. The current study investigated the use of chrysolaminarin-rich O. aurita as an immunostimulant in the diet of juvenile golden pompano Trachinotus ovatus. Three experimental diets containing 0%, 1% and 5% O. aurita were used to feed T. ovatus for 6-week. The results indicated that diet supplementation with O. aurita powder boosted the growth of T. ovatus by decreasing the feed conversion ratio, increasing the activities of lipase and pepsin in the intestine, and improving intestinal villi structure. Supplementation with 5% O. aurita promoted its antioxidant capacity by stimulating the Nrf2-ARE signal pathway and enhancing the total antioxidant capacity and activities of catalase, superoxide dismutase, and glutathione peroxidase. It also exerted hepatoprotective effects by inhibiting lipid deposition and downregulating the expression of proinflammatory cytokines and apoptosis-related genes, as well as improving the nonspecific immune response by increasing the expression levels of c-type lysozyme and complement 4. Therefore, a diet supplemented with 5% O. aurita is recommended to enhance the growth, antioxidant ability, and immunity of T. ovatus.

Effects of dietary leucine on glucose metabolism, lipogenesis and insulin pathway in juvenile golden pompano Trachinotus ovatus

The aim of the study was to evaluate the effects of dietary leucine on the insulin signaling pathway, glucose metabolism and lipogenesis in juvenile golden pompano T. ovatus. A total of 300 juvenile golden pompano (9.15 ± 0.04 g) were fed four isonitrogenous diets with graded levels of leucine (1.25 %, 2.77 %, 5.84 and 8.73 %) for 8 weeks. They were randomly distributed to 12 cages (1.0 m × 1.0 m × 1.5 m; three cages per treatment) at an equal stocking rate of 25 fish per cage. Results indicated that compared with 1.25 % (the control), 2.77 % dietary leucine upregulated the relative expressions of IRS-1, PI3K, AKT and TOR, while 8.73 % dietary leucine lowered the relative expression of IRS-1. Compared with 1.25 % (the control), 5.84 % and 8.73 % dietary leucine significantly upregulated the relative expression of S6K1. Compared with 1.25 % (the control), 2.77 % dietary leucine led to the increment of the expression levels of GK, PK, GS and GLUT2, and the plasma insulin level, while led to inhibition of PEPCK. Compared with 1.25 % (the control), 8.73 % dietary leucine significantly decreased the relative expressions of PK and GLUT2, and plasma insulin level, while increase the relative expressions of G6Pase and PEPCK, plasma glucose level. Compared with 1.25 % (the control), 2.77 % dietary leucine significantly upregulated the relative expression of G6PDH, FAS, ACC SREBP1, plasma triglyceride level. Furthermore, 8.73 % dietary leucine resulted in low plasma triglyceride content. Our results suggest that the PI3K/AKT/TOR insulin signaling pathway mediates chronic leucine supplementation induced hepatic glucose metabolism and lipogenesis in juvenile T. ovatus. Optimal level of leucine could activate insulin signaling pathway, thus enhance the glycolysis and fatty acid synthesis in juvenile T. ovatus, while dietary excess leucine resulted in hyperglyceria by reducing the insulin signaling pathway and improving gluconeogenesis.

Effects of different dietary oil sources on growth performance, antioxidant capacity and lipid deposition of juvenile golden pompano Trachinotus ovatus

Vegetable oils (VO) that are used to substitute fish oil in aquafeeds may affect, not only the fatty acid composition, but also lipid metabolism and distribution. The present study was designed to investigate this issue in juvenile golden pompano Trachinotus ovatus fed eight diets formulated with typical VO with widely varying fatty acid compositions including coconut oil (CO), palm oil (PO), oil-tea camellia seed oil (OTO), olive oil (OO), canola oil (CNO), peanut oil (PNO), linseed oil (LO) and perilla oil (PFO), in comparison with fish fed fish oil (FO). After the 8-week feeding trial, fish fed the CO diet had the highest growth performance, and higher general antioxidant capacities in serum and liver than in fish fed the other VO. The crude lipid content in whole body and expression levels of fas were lower in fish fed the FO, PFO and LO diets, while lipid contents and expression levels of scd were higher in fish fed the OTO and PNO diets. Other than fish fed the PFO diet, the total lipid contents of liver in other fish fed the other VO diets were higher than that in fish fed the FO diet, with the highest contents in fish fed the OTO and OO diets. The expression levels of genes involved in fatty acid catabolism and transport, namely pparα, cpt1 and apoB100, were higher in fish fed diet PFO than in fish fed the other diets. Comparing the fatty acid compositions of tissues and diets showed that 18:1n-9, 18:3n-3 (ALA) and 22:6n-3 (DHA) were preferentially deposited in tissues of pompano, with DHA preferentially deposited in polar lipids rather than neutral lipids. However, excessive dietary ALA in PFO did not lead to increased deposition of ALA, but increased liver lipid content. The present study showed that dietary lipid sources had significant influences on growth performance and antioxidant capacity, as well as on lipid deposition. Low dietary 18:1n-9, high n-3 long-chain polyunsaturated fatty acids and an appropriate ratio of ALA/LNA (18,2n-6) could reduce lipid deposition in pompano tissues, especially liver.

Effects of dietary n-3 highly unsaturated fatty acids levels on growth, lipid metabolism and innate immunity in juvenile golden pompano (Trachinotus ovatus)

To investigate the effects of dietary n-3 highly unsaturated fatty acids (HUFA) levels on growth, lipid metabolism and innate immunity in juvenile golden pompano Trachinotus ovatus, a marine carnivorous teleost, a total of 450 fish (average body weight: 14.84 g) were randomly distributed into 18 cages at sea, each dietary group with three cages and respectively fed six diets (D1-D6) with 2.30% (D1), 0.64% (D2), 1.00% (D3), 1.24% (D4), 1.73% (D5), or 2.10% (D6) n-3 HUFA. Here, D1 with fish oil as lipid source was set as control, while D2-D6 used a mixed vegetable oil as lipid source and supplemented with docosahexaenoic acid- (DHA) and eicosapentaenoic acid- (EPA) enriched oils to adjust the n-3 HUFA levels. After 8 weeks feeding, the daily growth coefficient (DGC), specific growth rate (SGR) and feed efficiency ratio (FER) showed no significant difference among the six dietary groups (P > 0.05). The levels of EPA and DHA in serum and liver increased with the dietary n-3 HUFA levels. The activity of total superoxide disumutase (T-SOD) in serum of fish fed D4 and D5 were significantly higher than that of the other groups, whereas the opposite was true for serum IL-1β and IL-6 levels as well as liver malondialdehyde (MDA) content. The mRNA levels of genes related to hepatic lipid metabolism including sterol regulatory element-binding protein-1 (srebp-1), fatty acid binding protein 1 (fabp1), peroxisome proliferators-activated receptor alpha (pparα), elongase of very long-chain fatty acids 5 (elovl5) and fatty acyl desaturase 2 (fads2) were down-regulated in fish fed the diets with high n-3 HUFA levels, while those of apolipoprotein b 100 (aprob 100) and carnitine palmitoyl transferase 1 (cpt1) increased significantly as increasing n-3 HUFA levels up to 1.73% (D2-D5), but decreased in the 2.10% n-3 HUFA group (D6). In addition, the expression levels of genes related to innate immunity including interleukin-10 (il-10) and transforming growth factor β1 (tgf-β1) increased significantly when dietary n-3 HUFA increased from 0.64% to 1.73%, whereas the opposite was true for the expression levels of nuclear factor kappa-B (nf-κb), interleukin-1β (il-1β), interleukin-6 (il-6) and interleukin-8 (il-8). Overall, the results indicated that dietary n-3 HUFA at 1.24–1.73% (D4-D5) can effectively improve fatty acid profiles, lipid metabolism, antioxidant capacity and immune response of golden pompano.

Effects of stocking density on the growth performance, serum biochemistry, muscle composition and HSP70 gene expression of juvenile golden pompano Trachinotus ovatus (Linnaeus, 1758)

Golden pompano (Trachinotus ovatus) is one of the most important cultured marine fish in Southeast Asia. Stocking density affects the growth performance and welfare of fish in aquaculture. A 70-day rearing experiment was performed to evaluate the effect of different stocking densities on the growth performance, feed conversion ratio, serum biochemistry, muscle quality, antioxidant capacity and HSP70 mRNA expression of juvenile golden pompano cultured in off-shore sea cages. The experimental design was completely randomized using three replications with three treatments: low (100 fish/m3), medium (200 fish/m3), and high (300 fish/m3) stocking densities. Fish growth decreased significantly, and the feed conversion ratio increased significantly with increasing stocking density (P < .05). The serum glucose concentration increased significantly (P < .05), and the total protein, total triglyceride and total cholesterol concentrations were significantly reduced with increasing stocking density (P < .05). High stocking density led to elevated serum cortisol levels and decreased thyroxine levels. There was a significant decrease in the muscular crude fat content with increasing stocking density (P < .05), while the moisture, ash and protein contents did not significantly differ among the groups (P > .05). In this experiment, superoxide dismutase, glutamine transaminase and total antioxidant capacity increased significantly with increasing stocking density (P < .05). The expression levels of heat shock protein 70 were significantly up-regulated in the liver, kidney and brain as stocking density increased (P < .05); however, there was no significant difference in the spleen (P > .05). Overall, high stocking density was a chronic stressor in this experiment and had a negative effect on the growth, feed conversion ratio and animal welfare of T. ovatus.

Effects of dietary vitamin C on growth, flesh quality and antioxidant capacity of juvenile golden pompanoTrachinotus ovatus

To investigate the effects of dietary vitamin C on growth, flesh quality and antioxidant capacity of juvenile golden pompano Trachinotus ovatus, a 56-day feeding trial with five graded levels of dietary VC (D1: 11.69, D2: 34.89, D3: 59.10, D4: 114.26 and D5: 227.93 mg VC per kg of diet) was performed on 375 fish (triplicate groups of 25 fish per diet, initial weight 13.57 ± 0.09 g). Results showed that fish of D3 group exhibited the maximum specific growth rate (SGR) and the highest liver enzymatic activities of catalase (CAT) and glutathione peroxidase (GSH-PX), which were consistent with the expression levels of cat and gsh-px. Besides, the D3 group also showed higher contents of protein and lipid, and lower cooking loss, drip loss and malondialdehyde content in muscle than D1 group. The docosahexaenoic acid proportion in muscle increased with increasing dietary VC levels. Furthermore, the lowest expression levels of carnitine palmitoyltransferase1 (cpt1) and peroxisome proliferator-activated receptor α (pparα) were detected in livers of D3 group. The optimum dietary VC level was 49.73 mg/kg from the broken-line analysis based on the SGR, in which better growth performance, antioxidative ability and flesh quality were observed in T. ovatus juveniles.

Effect of dietary sodium butyrate on growth performance, enzyme activities and intestinal proliferation‐related gene expression of juvenile golden pompanoTrachinotus ovatus

The present study was conducted to investigate the effects of dietary sodium butyrate on growth performance, intestine enzyme activities and intestinal proliferation‐related gene expression of juvenile golden pompano Trachinotus ovatus. A basal diet was supplemented with sodium butyrate at 0.0 (control), 0.25, 0.5, 1, 2 and 4 g/kg feed for 8 weeks. The final body weight, weight gain (WG), specific growth rate (SGR) and condition factor (CF) increased with increasing dietary sodium butyrate up to 2.0 g/kg, and thereafter declined, while feed conversion ratio exhibited an opposite trend. Compared with the control, the 2.0 g/kg sodium butyrate group had higher condition factor (CF) significantly (p < 0.05). Whole body ash decreased with increasing dietary sodium butyrate level, with the lowest whole body ash content in 4.0 g/kg sodium butyrate (p < 0.05). Compared with the control, the 2.0 g/kg sodium butyrate group had significantly increased plasma glucose, cholesterol, albumin level, A/G ratio, ALT and AST contents (p < 0.05), while significantly decreased plasma ALT/AST ratio (p < 0.05). As for the intestinal digestive and brush border enzymes activities, compared with the control, the 2.0 and 4.0 g/kg sodium butyrate groups had significantly increased intestinal protease, amylase, AKP and Na⁺‐K⁺‐ATPase activities (p < 0.05), respectively. The relative level of intestinal CDX2 mRNA of fish significantly increased with dietary sodium butyrate level. Compared with the control, the 2.0 g/kg sodium butyrate groups had significantly increased the expression of intestinal CDX2 and CREB mRNA (p < 0.05), respectively. In conclusion, these results suggested that the optimum sodium butyrate level for juvenile golden pompano could be 2.0 g/kg of the diet.

Molecular characterization of G-type lysozyme from juvenile golden pompano Trachinotus ovatus and the regulation of its activity and expression by dietary sodium butyrate levels

The G-type lysozyme gene, non-specific immune molecule, was cloned from intestine of golden pompano (Trachinotus ovatus) by degenerate oligonucleotide primed PCR, including a complete open reading frame (ORF) of 804 bp. Homological protein analysis showed that the To-lysG in golden pompano shared a high degree of sequence identity with other known lysG sequences. In addition, tissue distribution analysis showed that To-lysG was expressed in nine tissues and had relatively high expression in spleen, head kidney and intestine. Then triplicate groups of golden pompano (18 cages) were fed twice daily to satiation with 0.0 (control), 0.25, 0.5, 1.0, 2.0 or 4.0 g kg−1 sodium butyrate (SB) diets for 8 weeks, respectively. Compared to the control group, 2.0 and 4.0 g kg−1 SB groups had higher lysozyme activities and the expression levels of To-lysG gene. After ammonia challenge, fish fed 1.0 g kg−1 SB group showed the highest survival rate (P < 0.05). Overall, these results suggest that the intestinal lysozyme activity and mRNA expression of T. ovatus were up-regulated significantly as dietary SB levels increased. These results indicated that To-lysG plays a crucial role in the regulation of intestinal immune function of dietary graded levels of SB in T. ovatus.

Effects of different dietary ratios of docosahexaenoic to eicosapentaenoic acid (DHA/EPA) on the growth, non-specific immune indices, tissue fatty acid compositions and expression of genes related to LC-PUFA biosynthesis in juvenile golden pompano Trachinotus ovatus

The n-3 long chain polyunsaturated fatty acid (n-3 LC-PUFA) such as docosahexaenoic and eicosapentaenoic acids (DHA and EPA) are essential fatty acids for marine carnivorous fish. Thus, the determination of optimal dietary DHA/EPA ratio is essential for the development of better feed formulation. In the present study, a marine carnivorous fish species, golden pompano (Trachinotus ovatus) juveniles were subjected to six isoproteic and isolipidic diets contained differential ratios of DHA/EPA (0.53, 0.81, 1.17, 1.48, 1.69, and 2.12) and a constant level of n-3 LC-PUFA (1.20% of the dry weight). After the 10-week feeding trial, fish fed the diet with DHA/EPA ratios of 1.17 and 1.48 achieved the best growth performance, with significantly higher weight gain (WG) and specific growth rate (SGR) than that fish fed the other diets (P < .05). At the DHA/EPA ratio of 1.48 group, non-specific immune indices, including the activities of lysozyme (LZM), catalase (CAT) and superoxide dismutase (SOD) in serum were significantly higher than those of other groups (P < .05). Fatty acid compositions of T. ovatus muscle, liver, eye and brain were significantly affected by the diets. The content of DHA and DHA/EPA in muscle, eye and brain both markedly increased with increasing dietary DHA/EPA ratios, and the concentration of DHA in brain was much higher than other tissues. Both the expression of elovl5-like and Δ6 fad in liver and the expression of elovl4-like and Δ6 fad in brain significantly increased with increasing dietary DHA/EPA ratios (P < .05). When subjecting the WG to the second-order polynomial regression analysis, the maximal growth was achieved at 1.40 of DHA/EPA ratio for the juvenile T. ovatus, which was thought as the recommended optimum requirement of dietary DHA/EPA ratio in the current study.

Effects of dietary dandelion extracts on growth performance, body composition, plasma biochemical parameters, immune responses and disease resistance of juvenile golden pompano Trachinotus ovatus

The present study was conducted to investigate the effects of dietary dandelion extracts (DE) supplementation on growth performance, feed utilization, body composition, plasma biochemical indices, immune responses, hepatic antioxidant abilities, and resistance to the pathogen Vibrio harveyi in Trachinotus ovatus. A basal diet supplemented with DE at 0, 0.50, 1.00, 2.00, 4.00 and 10.00 g kg−1 were fed to golden pompano for 8 weeks. The study indicated that dietary supplementation with DE could significantly improve final body weight (FBW), weight gain rate (WGR), specific growth rate (SGR), feed efficiency ratio (FER), feed intake (FI), protein efficiency ratio (PER) and protein deposit rate (PDR) (P < 0.05). The highest FBW, WGR, SGR, FI and PDR were observed in fish fed 1.00 g kg−1 dietary DE (P < 0.05). The highest FER and PER were recorded at 0.50 g kg−1 dietary DE (P < 0.05). Condition factor, viscerosomatic index, hepatosomatic index and survival were not significantly different among all groups. Fish fed 1.00 g kg−1 dietary DE showed significant increase in plasma total protein, complement 4 content and alkaline phosphatase, lysozyme, glutathione reductase (GSR) activity, but significant decrease in triglyceride, low density lipoprotein cholesterol, malondialdehyde (MDA) content and aspartate aminotransferase activities compared to the control group (P < 0.05). Hepatic antioxidant enzymes (SOD, T-AOC, CAT, GSH-Px, GSR) significantly increased whereas MDA content significantly decreased in fish fed 1.00 g kg−1 DE supplement (P < 0.05). After challenge with Vibrio harveyi, significant higher post-challenge survival was observed in fish fed DE supplement (P < 0.05). These results indicated that golden pompano fed a diet supplemented with DE (especially at 1.00 g kg−1 of fed supplement) could significantly promote its growth performance, feed utilization, body protein deposit, immune ability, hepatic and plasma antioxidative enzyme activities and improve its resistance to infection by Vibrio harveyi.

Effects of dietary leucine on growth performance, feed utilization, non-specific immune responses and gut morphology of juvenile golden pompano Trachinotus ovatus

The effects of dietary leucine on growth performance, feed utilization, non-specific immune responses and gut morphology were studied in juvenile golden pompano (Trachinotus ovatus) using 8-week feeding trials. Six isonitrogenous and isolipidic diets were formulated to contain six graded levels of dietary leucine (16.2, 20.9, 26.0, 30.7, 35.9 and 41.0gkg−1 leucine of dry diet). Each diet was randomly assigned to triplicate groups of 20 juvenile fish (5.76±0.06g). Maximum weight gain rate (WG), specific growth rate (SGR), feed intake (FI), protein efficiency ratio (PER), microvilli numbers and microvilli length in foregut and midgut were recorded at 30.7gkg−1 dietary leucine. Protein deposition ratio (PDR), hemoglobin (HGB) and hematocrit (HCT) were found to be optimal in fish fed with 35.9gkg−1 leucine of diet. Dietary leucine levels had a significant effect on serum superoxide dismutase (SOD), malondialdehyde (MDA), lysozyme (LZY) and total antioxidant capacity (T-AOC) (P<0.05). Intestinal microstructures were positively affected by dietary leucine at the optimal levels of 26.0 and 30.7gkg−1, significantly (P<0.05) increasing microvilli numbers and microvilli length in foregut and midgut. Based on the growth performance, feed utilization, proximate composition, serum enzyme activities and gut morphology, the optimum dietary leucine level for optimal growth of juvenile golden pompano was 29.3–32.9gkg−1 of the dry diet, corresponding to 71.5–80.2gkg−1 of dietary protein. Statement of relevanceThe study indicated low or excess amount of dietary leucine decreased growth performance, serum total antioxidant capacity and had a significantly negative effect on gut morphology. The optimum dietary leucine level for juvenile golden pompano was 2.93–3.29% of the dry diet. The results provide a theoretical basis for the designing of feed formulation for golden pompano (T. ovatus).

Effect of Dietary Marine Red Yeast Rhodotorula mucilaginosa on the Growth Performance, and also Non-Specific Immune Responses of Juvenile Golden Pompano Trachinotus Ovatus when Challenged with Vibrio Harveyi

The present study was conducted to investigate the effects of dietary marine red yeast Rhodotorula mucilaginosa supplementation on the growth performance, non-specific immune responses, and resistance to the pathogen Vibrio harveyi in Golden Pompano Trachinotus ovatus. A basal diet was supplemented with R. mucilaginosa at 0‰ (control), 1‰, 2‰, 3‰, 4‰, and 5‰ for 8 weeks. After the 8-week feeding trial, weight gain (WG) and specific growth rate (SGR) were significantly affected by the R. mucilaginosa levels, with the highest WG and SGR occurring at the 1‰ R. mucilaginosa level (P&lt;0.05). Compared to the control, the 4 and 5‰ R. mucilaginosa groups had significantly increased lysozyme (LYZ) and alkaline phosphatase (AKP) activity, but a decrease in nitric oxide synthase (NOS) was noted (P&lt;0.05). Compared to the control, the 2, 3 and 4‰ R. mucilaginosa groups had significantly increased hepatic superoxide dismutase (SOD) activity (P&lt;0.05), while hepatic malondialdehyde (MDA) content decreased significantly (P&lt;0.05). After challenge with V. harveyi, the group supplemented with 1‰ R. mucilaginosa had 100% survival rate. In addition, compared to the control group prior to challenge, the serum C3 level significantly increased in the group supplemented with 2‰ R. Mucilaginosa (P &lt; 0.05). Compared to the control 12 h and 48h after challenge, serum C4 levels in the 4‰ R. Mucilaginosa group increased significantly (P&lt;0.05). Our results suggest that ingestion of a basal diet supplemented with 1-3‰ R. mucilaginosa in T. ovatus could enhance resistance against the pathogen Vibrio harveyi.

Effects of Dietary Arachidonic Acid Levels on Growth Performance, Whole-Body Proximate Composition, Digestive Enzyme Activities and Gut Morphology of Juvenile Golden Pompano Trachinotus

The effects of dietary arachidonic acid (ARA) levels on growth performance, whole-body proximate composition, digestive enzyme activities, and gut morphology were studied in juvenile golden pompano Trachinotus ovatus. Six diets were formulated with six levels of ARA. Fish were fed twice daily to apparent satiation for 56 days (8 weeks). Weight gain (WG), specific growth rate (SGR), protein efficiency ratio (PER), feed conversion ratio (FCR), and viscerosomatic index (VSI) were significantly affected by dietary ARA levels (P &lt; 0.05). WG, SGR and PER increased with the increasing levels of ARA (P &lt; 0.05), and thereafter slightly declined (P &gt; 0.05); they were highest in fish fed the diet with 0.51% ARA and the lowest in fish fed the diet containing 0.15% ARA. Linear regression analysis on SGR indicated that the recommended optimum dietary ARA level for optimal growth of juvenile golden pompano was 0.53%. Whole body protein significantly declined when dietary ARA levels increased from 0.15% to 0.88% (P &lt; 0.05), and were lowest in fish fed the diet containing 0.88% ARA. The whole body lipid content showed an opposite trend compared with whole body protein. Pepsin activities showed no significant differences among treatments (P &gt; 0.05), while lipase activities of fish were significantly influenced by dietary ARA levels (P &lt; 0.05). The number of goblet cells and intestinal villus length increased with increasing levels of ARA from 0.15% to 0.51% (P &lt; 0.05), and decreased thereafter. Goblet cells of fish fed diets with 0.36%, 0.51%, 0.71% ARA were higher than in the other groups (P &lt; 0.05).

Effects of dietary soybean isoflavones on non-specific immune responses and hepatic antioxidant abilities and mRNA expression of two heat shock proteins (HSPs) in juvenile golden pompano Trachinotus ovatus under pH stress.

This study determined the effect of dietary soybean isoflavones on non-specific immunity and on mRNA expression of two HSPs in juvenile golden pompano Trachinotus ovatus under pH stress. Six diets were formulated to contain 0, 10, 20, 40, 60 and 80 mg/kg of soybean isoflavones. Each diet was fed to triplicate groups of fish in cylindrical tanks. After 56 days of feeding, 15 fish per tank were exposed to pH stress (pH ≈ 9.2) for 24 h. Serum total protein (TP), respiratory burst activity (RBA), alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (AKP), lysozyme (LYZ), complement 3 (C3), complement 4 (C4), cortisol, hepatic total antioxidant capacity (T-AOC), superoxide dismutase (SOD), malondialdehyde (MDA), catalase (CAT) and the relative mRNA expression of heat shock protein 70 (HSP70) and 90 (HSP90) were investigated. The results showed that after pH stress, serum TP, RBA, LYZ, C4, hepatic T-AOC and CAT levels were significantly reduced (P < 0.05) while serum ALT, hepatic MDA and HSP70 and HSP90 mRNA expression levels were significantly increased (P < 0.05). On the other hand, supplementation with soybean isoflavones significantly reduced levels of serum ALT (20, 40, 60 mg/kg soybean isoflavones groups) and hepatic MDA (40, 60 and 80 mg/kg soybean isoflavones groups). Supplemented groups had increased serum TP content (40 mg/kg soybean isoflavones groups), RBA (20 and 40 mg/kg soybean isoflavones groups), LYZ (40 and 60 mg/kg soybean isoflavones groups), C3(20, 40, 60 and 80 mg/kg soybean isoflavones groups), hepatic SOD activity (40, 60 and 80 mg/kg soybean isoflavones groups) as well as increased relative mRNA expression of hepatic HSP70 (40, 60 and 80 mg/kg soybean isoflavones groups) and HSP90 (40 and 60 mg/kg soybean isoflavones groups) (P < 0.05). These results indicate that ingestion of a basal diet supplemented with 40-60 mg/kg soybean isoflavones could enhance resistance against pH stress in T. Ovatus to some degree.

The Effects of dietary soybean isoflavones on growth, innate immune responses, hepatic antioxidant abilities and disease resistance of juvenile golden pompano Trachinotus ovatus

The present study was conducted to investigate the effects of dietary soybean isoflavones (SI) supplementation on growth performance, innate immune responses, hepatic antioxidant abilities, heat shock protein 70 (HSP70) gene expression and resistance to the pathogen Vibrio harveyi in Trachinotus ovatus. A basal diet was supplemented with SI at 0, 10, 20, 40, 60, 80 mg kg−1 feed for 8 weeks. Significantly maximum weight gain (WG) and specific growth rate (SGR) were observed in treatment with 40 mg kg−1 SI supplement (P < 0.05). Feed conversion ratio (FCR), feeding rate (FR) and survival rate were not significantly different among treatments. Fish fed a diet with 40 mg kg−1 SI showed significant increase in plasma total protein content, complement 3 content, lysozyme activity as well as respiratory burst activity, but decrease in alanine aminotransferase and aspartate aminotransferase activities (P < 0.05). Increased plasma alkaline phosphatase activity, hepatic total antioxidative capacity, catalase activity and superoxide dismutase activity were also noticed in fish fed SI at 40 or 60 mg kg−1 (P < 0.05). On the contrary, the lowest hepatic malondialdehyde (MDA) content was observed in fish fed SI at 40 mg kg−1 (P < 0.05). Compared with the control, the relative level of HSP70 mRNA in fish fed SI at 40–80 mg kg−1 were significantly increased, respectively (P < 0.05). After challenge with V. harveyi, significant higher post-challenge survival was observed in fish fed diets with 40–80 mg kg−1 SI supplement than that in control group (P < 0.05). These results indicated that dietary intake containing SI could enhance the immune ability of fish and improve its resistance to infection by V. harveyi. Especially supplementation with 40 mg kg−1 SI to the fish for 8 weeks showed remarkable improvement in the growth, non-specific immune responses, hepatic antioxidant abilities and HSP70 gene expression.

Effect of dietary arginine levels on the growth performance, feed utilization, non-specific immune response and disease resistance of juvenile golden pompano Trachinotus ovatus

In order to assess dietary arginine requirement for juvenile golden pompano, an experiment of six different diets with six dietary arginine levels (2.05%, 2.38%, 2.65%, 2.98%, 3.25% and 3.58%) was conducted. The results showed that the content of dietary arginine had a significant effect on weight gain (WG), specific growth rate (SGR), feed conversion rate (FCR) and protein efficiency ratio (PER) of golden pompano (P 0.05). Dietary arginine content had a significant effect on serum and hepatic total nitric oxide synthase and lysozyme activities as well as survival rate in a Vibrio harveyi challenge experiment (P < 0.05). Quadratic regression analysis on WG, SGR, FCR and PER indicated that the recommended optimum dietary arginine level for optimal growth of juvenile pompano was 2.73–2.74% of the dry diet, corresponding to 6.32–6.35% of dietary protein.

Effect of salinity on the rearing performance of juvenile golden pompanoTrachinotus ovatus(Linnaeus 1758)

Effect of rearing salinity on the performance of juvenile golden pompano Trachinotus ovatus (Linnaeus 1758) was studied under a laboratory condition. Fish growth, survival, RNA/DNA ratio, pepsin activity, α-amylase activity and FCR were used as evaluation criteria. The growth and RNA/DNA ratio were significantly affected by the rearing salinity. High growth rate and RNA/DNA ratio were observed when fish were reared at the salinity of 34‰. The pepsin activity of fish was not significantly affected by the rearing salinity. However, the α-amylase activity of fish was significantly affected by the rearing salinity. The α-amylase activity of fish reared at the salinity of 10‰ was significantly lower than fish cultured at the salinity of 34‰. Rearing salinity can significantly affect the FCR of juvenile golden pompano. The FCR of fish cultured at the salinity of 10‰ was 5-times higher than the FCR of fish reared at 34‰. Results from the present study indicate that juvenile golden pompano can be reared above 26‰ without affecting fish performance, and the salinity of 10‰ may be too low to rear juvenile golden pompano as fish growth, RNA/DNA ratio and α-amylase activity were reduced.

Salinity regulates antioxidant enzyme and Na+K+-ATPase activities of juvenile golden pompanoTrachinotus ovatus(Linnaeus 1758)

Effects of salinity on the growth, survival, superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPX) and sodium-potassium adenosine triphosphatase (Na+K+-ATPase) activities of juvenile golden pompano Trachinotus ovatus were studied under a laboratory condition. Experimental fish were reared at the salinities of 10‰, 18‰, 26‰ and 34‰ for 30 days. Growth and survival of juvenile golden pompano were significantly affected by the rearing salinity. Fish reared at 34‰ achieved the highest specific growth rate, while the highest survival was obtained when fish were cultured at the salinity of 26‰. The highest GPX activity was obtained when fish were cultured at 26‰, and the lowest GPX activity was observed when fish reared at 34‰ salinity. The SOD activities of fish reared at 18‰ and 34‰ were significantly higher than those reared at 10‰ and 26‰. The lowest of Na+K+-ATPase activity was obtained in fish reared at 34‰, while the highest Na+K+-ATPase activity was obtained when fish reared at 18‰. Results from present study indicate that juvenile golden pompano can be reared above 18‰ without sacrificing fish survival, and the best growth can be achieved when fish is reared at the salinity of 34‰. The salinity of 10‰ may be too low for juvenile golden pompano as the growth, survival and SOD activity were reduced.