Effects of dietary inorganic copper on growth performance and immune responses of juvenile beluga,Huso huso

A 12‐week feeding trial was conducted to evaluate the optimum dietary inorganic copper (copper sulphate) in juvenile beluga, Huso huso. Eight semi‐purified diets containing 1.1 (Cu_1.0), 3.5 (Cu_4.0), 7.1 (Cu_7.0), 9.7 (Cu₁₀), 13.1 (Cu₁₃), 25.1 (Cu₂₅), 49.9 (Cu₅₀) and 195 (Cu₁₉₅) mg Cu kg^?1 diet in the form of CuSO₄.5H₂O were fed to fish of initial body weight 8.49 ± 0.32 g and length 11.85 ± 0.66 cm (mean ± SD) in triplicate groups in a flow‐through system. Weight gain (WG) of fish fed Cu₁₀ and Cu₁₃ diets was significantly higher than that of fish fed Cu_1.0, Cu_4.0, Cu₂₅, Cu₅₀ and Cu₁₉₅ diets (P < 0.05). Whole‐body and muscle crude protein increased with dietary Cu up to the supplementation level of 13.1 mg kg^?1 diet and then decreased. Whole‐body lipid content was negatively correlated, while whole‐body ash was positively correlated with dietary copper concentration. Hepatic copper–zinc superoxide dismutase activity of fish fed Cu₁₀ and Cu₁₃ diets was significantly higher than that of fish fed Cu_1.0, Cu_4.0 and Cu₁₉₅ diets. Hepatic thiobarbituric acid‐reactive substances of fish fed Cu₁₃ diet was significantly lower than those of fish fed the other diets except for that of fish fed Cu₁₀ diet. Aspartate aminotransferase, alanine aminotransferase and copper accumulation in tissues increased with dietary copper. Broken‐line analysis of WG suggested that the optimum dietary Cu level was 10.3 mg Cu kg^?1 diet. Therefore, these results may indicate that the optimum dietary Cu levels could be greater than 10.3 mg Cu kg^?1 diet but less than 13.1 mg Cu kg^?1 diet in juvenile beluga, when copper sulphate is used as the dietary source of inorganic copper.     

Effects of different dietary levels of L-ascorbyl-2-polyphosphate on growth and tissue vitamin C concentrations in juvenile olive flounder, Paralichthys olivaceus (Temminck et Schlegel)

This experiment was conducted to study the effects of different dietary levels of vitamin C, L‐ascorbyl‐2‐polyphosphate (ASPP), on growth and tissue vitamin C concentrations in juvenile olive flounder, Paralichthys olivaceus (Temminck et Schlegel). Fish were fed one of six semi‐purified diets containing an equivalent of 0, 25, 50, 75, 150, or 1500 mg ascorbic acid (AA) kg^?1 diet (C₀, C₂₅, C₅₀, C₇₅, C₁₅₀ or C₁₅₀₀) in the form of ASPP for 12 weeks. Weight gain (WG) and protein efficiency ratio (PER) of fish fed the C₀ diet were significantly lower than those of fish fed the other diets (P < 0.05), and WG and PER of fish fed the C₂₅, C₅₀ and C₇₅ diets were significantly lower than those of fish fed the C₁₅₀₀ diet (P < 0.05). Fish fed the C₀ diet exhibited vitamin C deficiency symptoms such as anorexia, scoliosis, cataract, exophthalmia and fin hemorrhage at the end of the 12‐week test. After 12 weeks of the feeding trial, AA concentrations from gill, kidney, and liver of fish fed the C₀, C₂₅, C₅₀ and C₇₅ diets were significantly lower than those of fish fed the C₁₅₀ and C₁₅₀₀ diets (P < 0.05). Based on broken line analyses for WG and PER, the optimum dietary levels of vitamin C were 91 and 93 mg AA kg^?1 diet respectively. These findings suggest that the dietary vitamin C requirement could be 93 mg AA kg^?1 diet to support reasonable growth, and greater than 150 mg AA kg^?1 diet may be required for AA saturation of major tissues for juvenile olive flounder under experimental conditions.     

Effects of dietary copper sources on growth,tissue copper accumulation and physiological responses of Japanese sea bass (Lateolabrax japonicus) (Cuvier, 1828) fed semipurified or practical diets

An 8‐week trial was conducted to compare the efficacy of a chelated copper (Cu) with the inorganic Cu (CuSO₄), in the diet of Japanese sea bass (Lateolabrax japonicus). Six diets were prepared based on two basal diets (semi‐purified or practical) at two Cu inclusion levels (0 and 4 mg kg^?1 from or chelated‐Cu), accordingly named as S0, SI4, SM4, P0, PI4 and PM4 respectively. Each diet was fed to quadruplicate groups of Japanese sea bass (initial weight: 65.0 ± 0.03 g) during the trial. Fish fed practical diets had higher feed intake, specific growth rate, protein efficiency rate (PER), liver Cu accumulation, liver Na⁺K⁺‐ATPase and plasma alkaline phosphatase, but lower hepatosomatic index than the groups fed semi‐purified diets (P < 0.05). Higher PER was exhibited by fish fed chelated‐Cu diets than that of fish fed CuSO₄ diets (P < 0.05). Although liver Cu accumulation was significantly higher in fish fed practical diets,, liver Cu content increased significantly with increasing dietary copper levels only in fish fed semipurified diets. Chelated‐Cu has higher efficiency than CuSO₄ when fed in practical diets. Poor growth performance of fish fed semipurified diets might induce underestimating the nutrient requirement of Japanese sea bass.     

Synergistic effects of dietary vitamin E and selenomethionine on growth performance and tissue methylmercury accumulation on mercury‐induced toxicity in juvenile olive flounder,Paralichthys olivaceus (Temminck et Schlegel)

An 8‐week feeding trial was conducted to evaluate the synergistic effects of dietary vitamin E and selenomethionine (SeMet) on induced methylmercury (MeHg) toxicity in juvenile olive flounder Paralichthys olivaceus. Nine semi‐purified diets were formulated to contain three different vitamin E levels as DL‐α‐tocopheryl acetate (0, 100 and 200 mg TAkg^?1 diet) and three different selenium (Se) levels (0, 2 and 4 SeMet mg kg^?1 diet) on the constant mercury toxicity level (20 mg MeHgkg^?1 diet). Nine experimental diets, in a 3² factorial design (E₀Se₀, E₀Se₂, E₀Se₄, E₁₀₀Se₀, E₁₀₀Se₂, E₁₀₀Se₄, E₂₀₀Se₀, E₂₀₀Se₂ and E₂₀₀Se₄), were fed to triplicate groups of fish averaging 2.3 ± 0.04 g (mean ± SD) in the semi‐recirculation system. After 8 weeks of feeding trial, vitamin E and Se showed significant effects on weight gain (WG) of fish (P < 0.05). We found that there was a clear trend of increasing WG with elevating vitamin E and Se levels in the diets. Feed efficiency (FE), specific growth rate (SGR), protein efficiency ratio (PER) and survivability exhibited a similar trend with WG. Both antioxidants had significant interaction effects on FE and PER (P < 0.05). Methylmercury concentrations in fish muscle, liver and kidney decreases in a dose‐dependent manner as dietary vitamin E and Se levels increase. Interestingly, the most significant interactive effects of vitamin E and Se were found in liver tissue for depleting Hg concentrations (P < 0.05). These findings suggest that dietary vitamin E more than 100 mg TA kg^?1 diet with 2 or 4 mg SeMet kg^?1‐supplemented diets could have synergistic effects on growth and liver mercury bioaccumulation on MeHg‐induced toxicity in juvenile olive flounder.     

Reevaluation of the Phosphorus Requirement of Juvenile Olive Flounder Pavalichfhys olivaceus and the Bioavailability of Various Inorganic Phosphorus Sources

A 6‐wk feeding trial was conducted to reevaluate the phosphorus (P) requirement of juvenile olive flounder and the bioavailability of various inorganic phosphorus sources (IPS). Eight experimental diets were prepared such that all diets contained the same amount of calories, nitrogen, and calcium. Each diet included 0.33% total phosphorus (TP) and 0.60 % total calcium supplied by the basal diet. The eight experimental diets were: the basal diet without P supplementation (BD), three diets consisting of the BD supplemented with NaH,PO₄.2H₂O (NaP_0.45 NaP_0.57 or NaP_1.14) to supply 0.45, 0.57 or 1.14% TP, and four diets consisting of the BD supplemented with K₂HPO₄ (KP_0.57), Ca(H₂PO₄)_;H₂O (Cap_0.57), CaH₂PO_4;2H₂O (CaHP_0.57) or flounder bone meal (FBP_0.57) to supply 0.57% TP. Fish (N = 480)averaging 4.02 ± 0.03 g (Mean ± SD) were distributed randomly into 24 aquaria (20 fish per aquarium), and were fed one of the eight experimental diets in triplicate groups. The weight gain (WG), specific growth rate (SGR), protein efficiency ratio (PER) and feed efficiency (FE) of fish fed the NaP_0.57 diet were significantly higher than those of fish fed the BD, NaP_1.14, KP_0.57, CaHP_0.57 and FBP_0.57 diets (P > 0.05). There was no significant difference in WG, SGR, PER, and FER among fish fed the Nap_0.45, NaP_0.57 and Cap_0.57, diets. Whole body P retention (WBP_ret) in fish fed the Nap_0.57 diet was significantly higher than in fish fed the BD, NaP_1.14, KP_0.57 CaHP_0.57 and FBP_0.57diets (P > 0.05). There was no significant difference in WBP_ret among fish fed the NaP_0.47, NaP_0.57, and CaP_0.57, diets. The ability of the fish to digest the phosphorus in the NaP_0.45, Nap_0.57, NaP_1.14, and CaP_0.57 diets was significantly better than that of fish fed the other diets (P > 0.05). These results indicated that the dietary P requirement for juvenile olive flounder could be 0.45457%. Also, NaH,PO_; 2H₂O and Ca(H₂PO₄)_;H₂O appeared to have a better bioavailability than the other P sources in juvenile olive flounder.     

Evaluation of optimum dietary protein-to-energy ratio in juvenile olive flounder Paralichthys olivaceus (Temminck et Schlegel)

An 8‐week feeding trial was conducted to estimate the optimum dietary protein to energy (P/E) ratio in juvenile olive flounder Paralichthys olivaceus. Eight experimental diets were formulated with two energy levels and four protein levels at each energy level. Two energy levels of 12.5 and 16.7 kJ g^?1 diets were included at crude protein (CP) levels of 25%, 30%, 35% and 45% with 12.5 kJ g^?1, and CP levels of 35%, 45%, 50% and 60% with 16.7 kJ g^?1. After 1 week of the conditioning period, fish initially averaging 8.1±0.08 g (mean±SD) were randomly distributed into the aquarium as groups of 15 fish. Each diet was fed on a dry‐matter basis to fish in three randomly selected aquariums at a rate of 3–5% of total wet body weight per day for 8 weeks. After 8 weeks of the feeding trial, weight gain (WG), feed efficiency ratio and specific growth rate of fish fed 45% CP with 16.7 kJ g^?1 energy diet were significantly higher than those from the other dietary treatments (P<0.05). WG of fish fed 12.5 kJ g^?1 energy diets increased with the increase of dietary protein levels. However, WG of fish fed 16.7 kJ g^?1 energy diets increased with the increase of dietary protein levels up to 45% CP and then decreased when fish fed 50% and 60% CP diets. Both dietary protein and energy affected protein retention efficiency and energy retention efficiency. Haemoglobin (Hb) of fish fed 35% and 45% CP diets with 12.5 kJ g^?1 energy were significantly high and not different from Hb of fish fed 45% and 50% CP diets with 16.7 kJ g^?1 energy. Haematocrit of fish fed 45% CP diet with 16.7 kJ g^?1 energy was significantly higher than those from fish fed 25% and 30% CP diets with 12.5 kJ g^?1 energy (P< 0.05). Based on the results of this experiment, we concluded that the optimum dietary P/E ratio was 27.5 mg protein kJ^?1 with diet containing 45% CP and 16.7 kJ g^?1 energy in juvenile olive flounder.     

Evaluation of Fermented Soybean Curd Residues as an Energy Source in Diets for Juvenile Olive Flounder, Paralichthys olivaceus

A 10‐wk feeding experiment was conducted to evaluate the potential use of fermented soybean curd residues (FSCR) as an energy source in diets for juvenile olive flounder, Paralichthys olivaceus. Five isonitrogenous and isoenergetic diets were formulated to contain dry soybean curd residues to replace wheat meal (WM) at the levels of 0, 25, 50, 75, and 100% (FSCR₀, FSCR₂₅, FSCR₅₀, FSCR₇₅, and FSCR₁₀₀, respectively). Fish averaging 6.00 ± 0.07 g (mean ± SD) were randomly distributed into 15 aquaria as groups of 15 fish and fed the experimental diets in triplicate at a rate of 4–5% of wet body weight per day twice daily on dry matter basis. At the conclusion of the feeding trial, weight gain (WG) and specific growth rate (SGR) of fish fed diet FSCR₂₅ were significantly higher than those of fish fed diets FSCR₅₀, FSCR₇₅, and FSCR₁₀₀ (P < 0.05); however, there were no significant differences in WG and SGR among fish fed diets FSCR₀ and FSCR₂₅ and among those fed diets FSCR₀ and FSCR₅₀. Feed efficiency and protein efficiency ratio of olive flounder fed diet FSCR₂₅ were significantly higher than those of fish fed diets FSCR₅₀, FSCR₇₅, and FSCR₁₀₀ (P < 0.05); however, there were no significant differences in these parameters among fish fed diets FSCR₀ and FSCR₂₅ and among those fed diets FSCR₀, FSCR₅₀, FSCR₇₅, and FSCR₁₀₀. Hematological characteristics, condition factor, hepatosomatic index, and survival rate of fish fed FSCR₀ were not significantly different from those of fish fed the other diets. These results indicated that FSCR could replace up to 50% WM as an energy source in juvenile olive flounder diets based on ANOVA test.     

Effect of dietary protein reduction with lysine and methionnine supplementation on growth performance,body composition and total ammonia nitrogen excretion of juvenile grass carp,Ctenopharyngodon idella

A 63‐day growth trial was undertaken to estimate the effects of supplemented lysine and methionine with different dietary protein levels on growth performance and feed utilization in Grass Carp (Ctenopharyngodon idella). Six plant‐based practical diets were prepared, and 32CP, 30CP and 28CP diets were formulated to contain 320 g kg^?1, 300 g kg^?1 and 280 g kg^?1 crude protein without lysine and methionine supplementation. In the supplementary group, lysine and methionine were added to formulate 32AA, 30AA and 28AA diets with 320 g kg^?1, 300 g kg^?1 and 280 g kg^?1 dietary crude protein, respectively, according to the whole body amino acid composition of Grass Carp. In the groups without lysine and methionine supplementation, weight gain (WG, %) and specific growth rate (SGR, % day^?1) of the fish fed 32CP diet were significantly higher than that of fish fed 30CP and 28CP diets, but no significant differences were found between 30CP‐ and 28CP‐diet treatments. WG and SGR of the fish fed 32AA and 30AA diets were significantly higher than that of fish fed 28AA diets, and the performance of grass carp was also significantly improved when fed diets with lysine and methionine supplementation (P < 0.05), and the interaction between dietary protein level and amino acid supplementation was noted between WG and SGR (P < 0.05). Feed intake (FI) was significantly increased with the increase in dietary protein level and the supplementation of lysine and methionine (P < 0.05), but feed conversion ratio (FCR) showed a significant decreasing trend (P < 0.05). Two days after total ammonia nitrogen (TAN) concentration test, the values of TAN discharged by the fish 8 h after feeding were 207.1, 187.5, 170.6, 157.3, 141.3 and 128.9 mg kg^?1 body weight for fish fed 32CP, 32AA, 30CP, 30AA, 28CP and 28AA diets, respectively. TAN excretion by grass carp was reduced in plant‐based practical diets with the increase in dietary protein level and the supplementation of lysine and methionine (P < 0.05). The results indicated that lysine and methionine supplementation to the plant protein sources‐based practical diets can improve growth performance and feed utilization of grass carp, and the dietary crude protein can be reduced from 320 g kg^?1 to 300 g kg^?1 through balancing amino acids profile. The positive effect was not observed at 280 g kg^?1 crude protein level.     

Evaluation of dietary yellow loess as an antibiotic replacer on growth,immune responses,serological characteristics and disease resistance in rainbow trout,Oncorhynchus mykiss

A 12 weeks of feeding trial was conducted to evaluate the effects of different levels of dietary yellow loess as an antibiotic (oxytetracycline) replacer in rainbow trout, Oncorhynchus mykiss. Five experimental diets were formulated to contain no antibiotics or yellow loess (control/CON), three graded levels of yellow loess 5 (YL₅), 10 (YL₁₀) and 20 g YL kg^?1 diet (YL₂₀) and oxytetracycline at 5 g OTC kg^?1 diet. Forty‐five fish averaging 39.4 ± 1.6 g (mean ± SD) were randomly distributed in to 15 aquaria. Triplicate groups of fish were fed one of the experimental diets at 1.5 ~ 1.9% of wet body weight per day. At the end of the feeding trial, average weight gain (WG) and specific growth rate (SGR) from fish fed CON diet were significantly lower than those from fish fed YL₁₀, YL₂₀ or OTC diets (P < 0.05). Lysozyme activity from fish fed YL₂₀ was detected to be significantly higher than that from fish fed CON diet (P < 0.05). While, superoxide dismutase (SOD) activity from fish fed YL₁₀ and YL₂₀ was recorded to be significantly higher than that from fish fed CON diet (P < 0.05). Fourteen days of challenge test with bacteria A. salmonicida showed significantly lower survival rate for CON than those of fish fed other experimental diets. Therefore, these results indicated that dietary yellow loess at 10–20 g kg^?1 could be a promising alternative of oxytetracycline in rainbow trout.     

Optimum dietary protein level for maximum growth of juvenile olive flounder Paralichthys olivaceus (Temminck et Schlegel)

This experiment was conducted to determine the optimum dietary protein level for juvenile olive flounder Paralichthys olivaceus (Temminck et Schlegel) fed a white fish meal and casein‐based diets for 8 weeks. Olive flounder with an initial body weight of 4.1 ± 0.02 g (mean ± SD) were fed one of the six isocaloric diets containing 35%, 45%, 50%, 55% and 65% crude protein (CP) at a feeding rate of 4–5% of wet body weight on a dry‐matter basis to triplicate groups of 20 fish per aquarium. After 8 weeks of feeding, per cent weight gain (WG) and feed efficiency ratios of fish fed the 55% CP diet were not significantly higher than those from fish fed the 50% and 65% CP diets, but significantly higher than those from fish fed the 35% and 45% CP diets. Fish fed the 50%, 55% and 65% CP diets had significant higher specific growth rates than did fish fed the 35% and 45% CP diets; however, there was no significant difference among fish fed the 50%, 55% and 65% CP diets. The protein efficiency ratio was inversely related to the dietary protein level; that is, maximum efficiency occurred at the lowest dietary protein level. Broken‐line model analysis indicated that the optimum dietary protein level was 51.2 ± 1.8% for maximum weight gain in juvenile olive flounder. The second‐order polynomial regression analysis showed that the maximum WG occurred at 57.7% and it revealed that the minimum range of protein requirement was between 44.2% and 46.4%. These findings suggest that the optimum dietary protein level for maximum growth could be greater than 46.4%, but less than 51.2% CP in fish meal and casein‐based diets containing 17.0 kJ g^?1 energy for juvenile olive flounder.     

Effects of the Dietary Fermented Tuna By‐product Meal on Growth,Blood Parameters,Nonspecific Immune Response,and Disease Resistance in Juvenile Olive Flounder,Paralichthys olivaceus

This study evaluated the effects of dietary fermented tuna by‐product meal (FTBM) in juvenile olive flounder, Paralichthys olivaceus. Five diets were formulated to replace fishmeal (FM) with FTBM at 0% (FTBM₀), 12.5% (FTBM_12.5), 25.0% (FTBM₂₅), 37.5% (FTBM_37.5), or 50% (FTBM₅₀). After 8 wk, weight gain, specific growth rate, and feed efficiency of fish fed FTBM₀ and FTBM_12.5 diets were significantly higher than fish fed the other diets (P < 0.05). Also, mean cumulative survival rates (%) of fish fed the FTBM₀ and FTBM_12.5 diets were significantly higher than those fed FTBM₅₀ diet at Day 9 postchallenge with Edwardsiella tarda (P < 0.05). Protein efficiency ratio of fish fed FTBM₀ and FTBM_12.5 diets was significantly higher (P < 0.05) than fish fed diets FTBM_37.5 and FTBM₅₀. Broken‐line regression analysis of weight gain showed an optimal FM replacement level of 10.65% with FTBM. Therefore, the optimal dietary inclusion of FTBM in juvenile olive flounder diets could be greater than 10.65% but less than 12.5% without any adverse physiological effects on fish health.     

Organic acids blend as dietary antibiotic replacer in marine fish olive flounder,Paralichthys olivaceus

The present study was conducted to evaluate the efficacy of organic acid blends as dietary antibiotic replacer in marine fish olive flounder, Paralichthys olivaceus. Fish averaging 3.5 ± 0.05 g (mean ± SD) were fed one of the four experimental diets: (1) without antibiotic or organic acid (Control/CON); (2) with antibiotic—50 mg oxytetracycline per kg body weight per day (OTC); (3) with organic acid blend A—4 g/kg diet (OA_A); and (4) with organic acid blend B—4 g/kg diet (OA_B), for 10 weeks. At the end of the experiment, total intestinal bacterial counts in fish‐fed OA_A, OA_B and OTC were significantly lower than that of fish‐fed CON diet (p < 0.05). Further, the group of fish‐fed organic acid blends (OA_A, OA_B) or antibiotic (OTC)‐supplemented diets exhibited lower intestinal Vibrio sp. counts compared with fish‐fed CON diet. Disease challenge test with bacteria Edwardsiella tarda showed significantly lower cumulative mortality rates for the group of fish‐fed OA_A, OA_B or OTC than that of fish‐fed CON diet (p < 0.05). There were no negative effects on the growth, serological characteristics and proximate composition among the group of fish‐fed different experimental diets. Therefore, the present experiment demonstrates that blends of organic acid could be a promising alternative to dietary antibiotics for the preventive and/or curative health management in marine fish olive flounder aquaculture.     

Dietary copper requirement of juvenile yellow catfish Pelteobagrus fulvidraco

The present experiment was conducted to quantify dietary copper (Cu) requirement for juvenile yellow catfish Pelteobagrus fulvidraco. The six experimental diets were formulated to contain the graded levels of CuSO₄·5H₂O (0, 0.005, 0.01, 0.02, 0.04 and 0.08 g kg^?1 diet respectively) providing the actual dietary copper values of 2.14 (control), 3.24, 4.57, 7.06, 12.22 and 22.25 mg Cu kg^?1 diet respectively. Each diet was fed to triplicate groups of yellow catfish (initial body weight: 3.13 ± 0.09 g, means ± SD) in an indoor static rearing system for 7 weeks. Fish fed the diet containing 3.24 mg Cu kg^?1 diet had the highest weight gain and specific growth rate, but they were not significantly different from that of fish fed the 4.57 and 7.06 mg Cu kg^?1 diets (P > 0.05). The poorest feed conversion rate, the lowest protein efficiency ratio, the lowest hepatosomatic index and viscerosomatic index were observed in fish fed the diet containing the highest Cu content diet (P < 0.05). Condition factor showed no significant differences among the treatments (P > 0.05). Proximate composition of fish body was significantly affected by dietary copper level (P < 0.05). Cu contents of whole body and liver increased with dietary Cu levels (P < 0.05), but muscle Cu content remained relatively stable (P > 0.05). Analysis by the second‐order regression of SGR and linear regression of whole‐body Cu retention of the fish indicated that dietary Cu requirements in juvenile yellow catfish were 3.13–4.24 mg Cu kg^?1 diet.     

Effects of dietary propolis supplementation on growth performance, immune responses, disease resistance and body composition of juvenile eel, Anguilla japonica

This study was conducted to investigate the effects of dietary propolis supplementation on growth performance, immune responses, disease resistance and body composition of juvenile eel, Anguilla japonica, in order to evaluate its bioavailability as a feed additive for this species. A total of 540 fish averaging 7.7?±?0.22?g (mean?±?SD) were randomly distributed into 18 tanks in groups of 30, and each tank was then randomly assigned to one of three replicates of six diets containing 0 (P₀), 0.25 (P_0.25), 0.5 (P_0.5), 1.0 (P₁), 2.0 (P₂) and 4.0 (P₄) % dietary propolis. At the end of 12?weeks of feeding trial, weight gain (WG), specific growth rate (SGR), feed efficiency (FE) and protein efficiency ratio (PER) of fish fed P_0.5 diet were significantly higher than those of fish fed P₀, P₁, P₂ and P₄ diets (P?<?0.05). These parameters were 148.9%, 0.72% day^?1, 94.4% and 2.9, respectively for fish fed P_0.5 diet. Serum lysozyme activity of fish fed P_0.5 (105.7 units mL^?1) and P₁ (106.0 units mL^?1) diets were significantly higher than those of fish fed P₀, P_0.25, P₂ and P₄ diets. Mucus lysozyme activity of fish fed P₁ (8.4 units 10?cm^?2) diet was significantly higher than those of fish fed P₀, P₂ and P₄ diets. Results indicated that the optimum dietary propolis supplementation levels could be 0.25?C0.5% for optimum growth and feed efficiency, and 0.5?C1% for enhanced immune responses and disease resistance in eel, A. japonica. This study may suggest that the dietary propolis level for the optimum immune responses could be higher than the level for the optimum growth of eel.     

Dietary ascorbic acid requirement of juvenile ayu (Plecoglossus altivelis)

To investigate dietary ascorbic acid (AA) requirement of juvenile ayu (Plecoglossus altivelis) weighing 1.27 ± 0.02 g, eight diets were formulated with graded levels (0, 20, 40, 80, 160, 320, 640 and 1280 mg AA kg^?1) of AA supplied as ascorbyl polyphosphate. Each experimental diet was fed to four‐replicate groups to apparent satiation three times a day for 8 weeks. At the end of the feeding trial, fish fed AA‐deficient diet showed visible AA deficiency signs and low survival. Based on the four‐parameter saturation kinetics model, the calculated AA requirement levels for each dose‐dependent response [weight gain, hepatic AA concentration, hydroxyproline (HyPro) concentration in skin and HyPro concentration in backbone] were 116, 226, 47 and 35 mg kg^?1, respectively. Based on the maximal growth performance, a level of 116 mg AA kg^?1 was recommended for commercial diet of juvenile ayu. To maintain tissue HyPro saturation and avoid AA deficiency symptoms, the minimum required dietary AA level was 47 mg kg^?1. Hepatic AA saturation was considered as the most stringent criterion for determination of AA requirement.     

Effects of dietary L‐carnitine level on growth performance,body composition and antioxidant status in beluga (Huso huso L. 1758)

A 17‐week feeding trial was carried out to evaluate the effects of dietary L‐carnitine level in beluga, Huso huso. A total of fish averaging 1247 ± 15.6 g (mean ± SD) were randomly distributed into 18 fibreglass tanks, and each tank holding 10 fish was then randomly assigned to one of three replicates of six diets with 50, 150, 350, 650, 950 and 1250 mg L‐carnitine kg^?1 diet. At the end of 17 weeks of feeding trial, average weight gain (WG), feed efficiency (FE), protein efficiency ratio (PER) and condition factor (CF) of fish fed 350 mg kg^?1 diet were significantly (P < 0.05) higher than those of fish fed 50, 150, 950 and 1250 mg kg^?1 diets. WG, FE, PER and CF of beluga fed 650 mg kg^?1 diet were also significantly higher than those of fish fed 50, 950 and 1250 mg kg^?1 diets. Whole body and muscle protein were significantly improved by the elevation of dietary L‐carnitine level up to 350 mg kg^?1. Liver superoxide dismutase and glutathione peroxidase activities of fish fed 350 and 650 mg kg^?1 diets were significantly higher than those of fish fed 50, 950 and 1250 mg kg^?1 diets. The dietary L‐carnitine level of 350–650 mg kg^?1 diet could improve growth performance, feed utilization, protein‐sparing effects of lipid, antioxidant defence system and reproductive success. Polynomial regression of WG suggested that the optimum dietary L‐carnitine level was 480 mg kg^?1 diet. Therefore, these results may indicate that the optimum dietary L‐carnitine could be higher than 350 but <650 mg kg^?1 diet in beluga reared in intensive culture conditions.     

Effects of Dietary β-1,3 Glucan and Feed Stimulants in Juvenile Olive Flounder, Paralichthys olivaceus

Abstract.— The present study was conducted to investigate the effects of dietary supplementation of β‐1,3 glucan and a laboratory developed feed stimulant, BAISM, as feed additives for juvenile olive flounder, Paralichthys olivaceus. Eight experimental diets were formulated to be isonitrogenous and isocaloric and to contain 50.0% crude protein and 16.4 kJ of available energy/g with or without dietary β‐1,3 glucan and BAISM supplementation. β‐1,3 glucan (G) and BAISM (B) were provided at 0% in the control diet (G₀B₀) and at 0.05% G + 0.45% B (G_0.05B_0.45), 0.05% G + 0.95% B (G_0.05B_0.95), 0.1% G + 0.90% B (G_0.1B_0.9), 0.10% G + 1.90% B (G_0.1B_1.9), 0.15% G + 1.35% B (G_0.15B_1.35), 0.15% G + 2.85% B (G_0.15B_2.85), and 0.30% G + 2.70% B (G_0.3B_2.7) in experimental diets. After the feeding trial, fish fed G_0.1B_0.9, G_0.1B_1.9, and G_0.15B_1.35 diets had higher percent weight gain (WG), feed efficiency ratio (FER), specific growth rate (SGR), protein efficiency ratio (PER), and condition factor (CF) than those fed G₀B₀, G_0.05B_0.45, G_0.05B_0.95, G_0.15B_2.85, and G_0.3B_2.7 diets (P < 0.05); however, there was no significant differences among fish fed G_0.1B_0.9, G_0.1B_1.9, and G_0.15B_1.35 diets. Fish fed G_0.1B_0.9 and G_0.1B_1.9 diets had higher chemiluminescent responses (CL) than those fed the other diets (P < 0.05). Lysozyme activity of fish fed G_0.1B_0.9 diet was significantly higher than that of fish fed the other diets (P < 0.05). These results indicated that the optimum dietary supplementation level of β‐1,3 glucan and BAISM could be approximately 0.10% β‐1,3 glucan + 0.90% BAISM (G_0.1B_0.9) of diet based on WG, FER, SGR, PER, CF, CL, and lysozyme activity in juvenile olive flounder, P. olivaceus.     

Effects of inorganic and chelated trace mineral (Cu,Zn, Mn and Fe) premixes in marine rockfish,Sebastes schlegeli (Hilgendorf), fed diets containing phytic acid

The present experiment was conducted to evaluate the effects of trace mineral (Cu, Zn, Mn and Fe) premixes from inorganic and chelated (chelated to 2‐hydroxy‐4‐methylthiobutanoic acid or hydroxy analog of methionine; Mintrex?, Novus International Inc., St. Charles, MO, USA) sources, in rockfish, (Sebastes schlegeli). fed diets containing mineral inhibitor phytic acid. Seven isonitrogenous (46% crude protein/CP) and isocaloric (16.63 KJ available energy per g diet) semi‐purified diets comprising of a Basal control and diets supplemented either with the inorganic (I) or chelated premix (M) at three different levels of 0.75 (I_0.75/M_0.75), 1.5 (I_1.5/M_1.5) and 3 (I₃/M₃) g kg^?1 diets were formulated. Twenty‐four fish averaging individual wet body weight of 9 ± 0.2 g (Mean ± SD) were fed one of the experimental diets in quadratic group for 16 weeks. Average weight gain (WG) of fish fed M₃ was significantly higher than that of fish fed Basal control and I_1.5 diets (P < 0.05). Whereas, data for the liver and whole body trace mineral contents showed a higher Cu and Zn saturation among fish fed M₃ and M_1.5 diets (P < 0.05). Furthermore, hepatic Cu‐Zn super oxide dismutase (Cu‐Zn SOD) activity was recorded to be highest for fish fed M₃ diet. Whereas, hepatic thiobarbituric acid‐reactive substance (TBARS) value was lowest in fish fed M₃ diet (P < 0.05). Challenge test with E. tarda showed an improved disease resistance among the fish fed different levels of trace mineral premixes. Therefore, these results demonstrated a higher efficiency of chelated compared to inorganic source of trace mineral premixes in marine rockfish.     

Effect of dietary vitamin C on the growth performance,antioxidant ability and innate immunity of juvenile yellow catfish (Pelteobagrus fulvidraco Richardson)

A 12‐week feeding trial was conducted to evaluate the effects of dietary vitamin C on growth performance, antioxidant status and innate immune responses in juvenile yellow catfish, Pelteobagrus fulvidraco. Six isonitrogenous and isolipidic diets (44% crude protein and 7% lipid) were formulated to contain six graded dietary vitamin C (ascorbate‐2‐poly‐ phosphate, ROVIMIX^® STAY‐C^® 35) levels ranging from 1.9 to 316.0 mg kg^?1 diet. The results of present study indicated that fish fed the lowest vitamin C diet had lower weight gain (WG) and specific growth rate (SGR) than those fed the diets supplemented vitamin C. WG and SGR did significantly increase with dietary vitamin C levels increasing from 1.9 to 156.5 mg kg^?1. However, no significant increase was observed with further dietary vitamin C levels increasing from 156.5 to 316 mg kg^?1. Survival, protein efficiency ratio and feed efficiency were not significantly affected by the dietary vitamin C levels. The activities of serum superoxide dismutase, catalase and glutathione peroxidase significantly increased when dietary vitamin C levels increased from 1.9 to 156.5 mg kg^?1, fish fed the lowest vitamin C diet had higher serum malondialdehyde content than those fed the diets supplemented with vitamin C. Fish fed the diet containing 156.5 mg kg^?1 vitamin C had the highest lysozyme, total complement activity, phagocytosis index and respiratory burst of head kidney among all treatments. The challenge test with Aeromonas hydrophila indicated that lower cumulative survival was observed in fish fed the lowest vitamin C diet. Analysis by broken‐line regression of SGR and lysozyme activity indicated that the dietary vitamin C requirement of juvenile yellow catfish was estimated to be 114.5 and 102.5 mg kg^?1 diet, respectively.     

Evaluation of dietary natural mineral materials as an antibiotic replacer on growth performance,non‐specific immune responses and disease resistance in rainbow trout,Oncorhynchus mykiss

We evaluated the effects of some dietary natural mineral materials as an antibiotic replacer based on growth performance, non‐specific immune responses and disease resistance in juvenile and subadult rainbow trout, Oncorhynchus mykiss. First experiment, juvenile rainbow trout averaging 2.7 ± 0.02 g (mean ± SD) were fed one of the six experimental diets; a basal commercial diet as a control (CON), CON with oxytetracycline (OTC), with yellow loess (YL), with Macsumsuk^® (MS), with Song‐Gang^® stone (SG) and with barley stone (BS) at 0.4% of each diet. At the end of 8‐week feeding trial, weight gain (WG), specific growth rate (SGR), feed efficiency (FE) and protein efficiency ratio (PER) of fish fed YL diet were significantly higher than those of fish fed CON diet. Non‐specific immune responses such as superoxide dismutase (SOD), myeloperoxidase (MPO), lysozyme (LYS) activity and oxidative radical production of fish fed YL diet were higher than those of fish fed CON diet. At the end of 15 days of challenge test with Aeromonas salmonicida, average cumulative survival rate of fish fed YL diet was significantly higher than that of fish fed BS and CON diets. However, there were no significant differences among fish fed YL, SG and OTC diets. Second experiment, subadult rainbow trout averaging 261.5 ± 3.5 g (mean ± SD) were fed one of the four experimental diets for 22 weeks: CON, and CON with OTC, YL or SG at 0.4% of each diet. At the end of feeding, growth performance of fish fed SG and YL diets was significantly higher than that of fish fed CON diet. Non‐specific immune responses in terms of SOD, MPO, LYS and NBT of fish fed SG and YL diets were significantly higher than those of fish fed CON diet. However, there were no significant differences among the fish fed YL, SG and OTC diets. The results indicate that dietary yellow loess or Song‐gang^® stone at 0.4% of diet could replace oxytetracycline in juvenile and subadult rainbow trout.