Dietary supplementation of red alga Pyropia spheroplasts on growth,feed utilization and body composition of sea cucumber,Apostichopus japonicus (Selenka)

A feeding experiment was conducted in a closed recirculating system to evaluate the effects of freeze‐dried spheroplasts prepared from Pyropia yezoensis (Ueda) on feed intake, growth and biochemical composition of sea cucumber, Apostichopus japonicus (Selenka). Pyropea spheroplasts (PS) were prepared through enzymatic treatment to break down the complex mixture of polysaccharides cell walls that might be easier for growth energy partitioning. Sea cucumbers were fed‐formulated diets with 10 (Diet 1), 30 (Diet 2) and 50 g/kg (Diet 3) inclusion level of PS. A diet without PS was used as a control (Diet 4). The experiment was conducted for 6 weeks maintaining water temperature 15 ± 1°C, photoperiod 18:06 hours (D:L). Feed was supplied ad‐libitum at 16.00 h once in a day, and the remaining feed and faeces were removed in the next day. Results showed that the highest growth was observed in the 50 g/kg PS diet compared to other treatments. Total weight gain, mean weight gain, net yield, protein efficiency ratio (PER) and protein gain (%) were significantly higher in the 50 g/kg PS diet (p < .05). A significantly higher percentage of energy was allocated for growth in the 50 g/kg PS diet. The highest specific growth rate and feed conversion efficiency (p < .05) were observed in the higher percentage of PS diet. Both the growth performance and biochemical analysis showed that superior growth was observed with increasing levels of PS in the diet. We infer that PS can be used as a new, cheaper feed ingredient in the formulated diet of A. japonicus.     

Assessing feasibility of replacement of fishmeal with enzyme‐treated feather meal in the diet of juvenile turbot (Scophthalmus maximus L.)

A feeding trial was conducted to examine the potential of enzyme‐treated feather meal (EFM) as a fishmeal substitute in the diet of turbot. Fishmeal (650 g/kg) was incrementally replaced (0, 160, 320, 480, 640 and 800 g/kg) by EFM (0, 80, 160, 240, 320, 400 g/kg) to prepare six experimental diets (Control, EFM8, EFM16, EFM24, EFM32 and EFM40). Diet EFM24 was supplemented with lysine and methionine to form seventh diet (EFM24 + AA). The eighth diet was formulated with 240 g/kg steam‐processed feather meal to replace 480 g/kg fishmeal (SFM24). Eight diets were each fed to triplicate groups of juvenile turbot (37.47 g) in a recirculating aquaculture system for 7 weeks. The results showed that fish fed diet EFM24 grew better than those fed SFM24 (p < .05). The growth performance, body composition and serum biochemical indices of fish fed diet EFM8 were not statistically different compared to the control treatment (p > .05). However, further increase in fishmeal replacement (32%–80%) affected negatively growth, nutrients digestibility, serum biochemical indices and body composition (p < .05). Supplementation of lysine and methionine (EFM24 + AA) significantly improved growth performance and diet utilization compared to EFM24 (p < .05). Altogether results suggested that the EFM could comprise 80 g/kg in a diet for juvenile turbot by concurrent reduction of the fishmeal content by 160 g/kg without lysine and methionine supplementation.     

The effect of ultrafiltered fish protein hydrolysate level on growth performance,protein digestibility and mRNA expression of PepT1 in juvenile turbot (Scophthalmus maximus L.)

The intention of the study was to investigate the effect of ultrafiltered fish protein hydrolysate (UF) level on growth, feed utilization, apparent digestibility coefficients and proximal intestine peptide transporter 1 (PepT1) mRNA level for juvenile turbot (Scophthalmus maximus L.). Experimental diets (UF‐0, UF‐5, UF‐10, UF‐15 and UF‐20) were prepared containing about 68% plant protein, and fish meal protein was, respectively, replaced by 0%, 5%, 10%, 15% and 20% UF of dietary protein. Diet PP contained about 78% plant protein, and diet CAA contained about 10% crystalline amino acid mixture. All diets were fed to seven triplicate groups of turbot (initial weight 16.05 ± 0.03 g) for 68 days. Fish fed diet UF‐10 had an increasing tendency in growth compared with diets contained UF, while dietary UF level was not significantly correlated with specific growth rate and feed intake. Feed efficiency, protein efficiency ratio and protein productive value significantly correlated with dietary UF level, and fish fed diets contained low‐level UF had higher digestibility than that diets UF‐0, PP and CAA. There was a decreasing tendency in PepT1 expression level with dietary UF level. The results indicated that low‐level UF showed a positive effect on growth and feed utilization in juvenile turbot.     

Effects of dietary chitosan oligosaccharide complex with rare earth on growth performance and innate immune response of turbot,Scophthalmus maximus L.

An 8‐week‐feeding trial was conducted to investigate the effect of dietary chitosan oligosaccharide complex with rare earth (COS‐REE) on growth performance and innate immune response of turbot, Scophthalmus maximus L. (Initial average weight was (12.1 ± 0.1) g) as well as disease resistance against Edwardsiella tarda. Six practical diets (approximately 53.01% protein and 12.57% lipid) were formulated to contain graded levels (0, 75, 150, 300, 600 and 1200 mg kg^?1) of COS‐REE. Results of the present study showed that, compared to the control group (0 mg kg^?1), the specific growth rate (SGR) was significantly higher in fish fed the diet with 300 mg kg^?1 COS‐REE (P < 0.05), while the feed conversion ratio (FCR) significantly decreased (P < 0.05). The phagocytic index (PI) and the activity of super oxide dismutase (SOD) of serum in fish fed the diet with 300 mg kg^?1 COS‐REE was significantly higher than fish fed the control diet (P < 0.05), but no significant differences were observed in malondialdehyde (MDA) and hepatic metallothionein (MT) concentrations. After 8 weeks, fish were challenged by intraperitoneal injection with E. tarda, and COS‐REE‐treated fish demonstrated increased protection capability. These results suggested that COS‐REE could enhance growth, innate immunity and disease resistance in turbot, and the optimum dose was approximately 300 mg kg^?1.     

Growth and economic analysis of freshwater prawn,Macrobrachium rosenbergii (de Man), produced with feeds substituting sunflower cake for fish meal,soya bean meal and mustard oil cake

A feeding trial with Macrobrachium rosenbergii was carried out to test the effectiveness of sunflower cake (SFC) as a replacement for conventional protein sources. Four isonitrogenous (~30% crude protein) and isocaloric (388–402 kcal) diets were formulated. Diet‐1 was a control made with conventional ingredients including fish meal, soya bean meal and mustard oil cake. Diet‐2, Diet‐3 and Diet‐4 were made with 30%, 40% and 50% SFC, respectively, replacing the usual protein sources used in Diet‐1. After 100 days, diets with SFC inclusion showed favourable growth and economic performance trends compared to control diet‐1, but without significant differences (p > .05). Better production (572.89 ± 62.99 kg/ha) was observed with Diet‐4 followed by Diet‐2, Diet‐3 and Diet‐1. Diet‐4 revealed the best feed conversion ratio (2.56 ± 0.24), specific growth rate (1.18 ± 0.05) and protein efficiency ratio (1.14 ± 0.10) among these diets. Whole carcass composition analysis revealed highest crude protein (18.19%) and lipid (4.43%) content in prawns fed Diet‐3 followed by Diet‐4. Highest total income, gross margin and benefit cost ratio (BCR) per hectare from prawns were US$5,759, US$2,623 and 1.84, respectively, found in Diet‐4. This study demonstrates that 30%–50% inclusion of SFC has favourable impacts on productivity and profitability compared with controls, with 50% SFC inclusion as the most cost‐effective diet for prawns without apparent compromise in growth, flesh quality or economics. The performances of the diets suggest that SFC may be a suitable substitute for fishmeal, soya bean meal and mustard oil cake in prawn feed. The effectiveness of higher SFC concentrations should also be investigated.     

Effect of dietary Yucca schidigera extract on growth,total ammonia–nitrogen excretion and haematological parameters of juvenile striped catfish Pangasianodon hypophthalmus

A feeding trial with striped catfish, Pangasianodon hypophthalmus was performed to determine the effect of Yucca schidigera in practical diet on the growth, feed utilization, body composition, total ammonia–nitrogen (TAN) excretion and haematological parameters. A diet with fish meal as the main protein source without yucca extract was used as the control diet (Diet 1). Four diets were formulated with 0.075 (Diet 2), 0.1 (Diet 3) and 0.15 (Diet 4)% of yucca extract respectively. Fifteen fish per tank (initial mean weight 1.78 ± 0.05 g) were randomly allocated to 15 fibreglass tanks (80‐L) connected to a freshwater closed recirculation system (temperature 29.7 ± 1.0°C). The experimental diets were tested in triplicates for 12 weeks. The specific growth rate of fish fed Diet 4 was significantly higher when compared with fish fed Diet 1. The growth of fish fed diets Diet 2 and Diet 3 were not significantly different compared with fish fed the Diet 1. Striped catfish fed Diet 4 had significantly lower feed conversion ratio compared with fish fed Diet 1 and Diet 2 (P < 0.05).The incorporation of high level Yucca schidigera extract in the diets reduced TAN compared with Diet 1. Dietary inclusion of Yucca extract levels did not significantly affect the biometric parameters or whole body proximate composition of the striped catfish (P > 0.05). The PCV (%) in fish significantly increased with high levels of Yucca inclusion (Diet 4) compared with control diet. Fish fed Diet 4 showed significantly higher haemoglobin levels than Diet 1 (P < 0.05). The results indicate that dietary inclusion of Yucca schidigera extract is promising as a feed additive that could improve growth performance and some haematological parameters and the best Yucca schidigera level was 0.15%.     

Effects of dietary soy isoflavones on growth,antioxidant status,immune response and resistance of juvenile grass carp (Ctenopharyngodon idella) to Aeromonas hydrophila challenge

The current study was conducted to evaluate the effect of dietary soy isoflavones (SI) on growth performance, antioxidant status, immune response and resistance to Aeromonas hydrophila in juvenile grass carp (Ctenopharyngodon idella). Six diets were formulated to contain 0 (control), 10, 50, 100, 500 or 1,000 mg SI per kg feed. Each diet was randomly allotted to triplicate net cages, and each net cage was stocked with 30 fish. The fish were fed one of the experimental diets to satiation twice per day for 60 days. The results showed that the WGR and DGC of the 500 mg/kg SI‐supplemented group were significantly higher than those of the non‐SI‐supplemented group (p < .05). Serum LZM and IgM activities in the SI‐supplemented groups were improved compared to the control group. SOD and GSH‐Px levels of fish fed the diet containing 500 mg/kg SI were significantly enhanced compared to those of fish fed the control diet (p < .05). Additionally, serum CAT, GSH‐Px and AKP activities in 50, 100 and 500 mg/kg SI‐supplemented groups were significantly higher than that in the control group (p < .05). The expression of most immune‐related genes (including IFN‐γ2, TNF‐α, M‐CSF2, IL‐6, IL‐12p40 and IL‐4) was significantly affected by dietary supplementation of SI. The group fed with 500 mg/kg SI had the highest 7‐day cumulative survival rate after challenge test (p < .05). The current results revealed that dietary inclusion of SI could improve the immune response and resistance against A. hydrophila and the supplementation level is suggested to be 500 mg/kg diet.     

Effects of dietary lysolecithin on growth performance,feed utilization,intestinal morphology and metabolic responses of channel catfish (Ictalurus punctatus)

This study investigated the effects of dietary lysolecithin on growth performance, feed utilization and metabolic responses of channel catfish (Ictalurus punctatus). Fish (initial weight: 14.77 ± 0.45 g) were randomly fed one of five practical diets supplemented with graded levels of lysolecithin (0, 125, 250, 375 and 500 mg/kg) in quadruplicate groups for 10 weeks. Results showed that no significant differences in weight gain, condition factor and viscerosomatic index among all the treatments. Fish fed diet supplemented with 250 mg/kg lysolecithin had significantly decreased feed conversion ratio and significantly increased protein efficiency ratio compared to that fed the control diet. The group with 250 mg/kg of dietary lysolecithin had higher protein and lower lipid contents in the whole body, and lower lipid content in the liver than those in the control group. Groups supplemented with 250–500 mg/kg of dietary lysolecithin had significantly higher gastric and intestinal lipase activities than the control group. Dietary lysolecithin at the level of 250 mg/kg significantly increased the activities of Na⁺, K⁺‐ATPase, alkaline phosphatase, total antioxidative capacity, total superoxide dismutase, glutathione peroxidase and catalase and significantly decreased the content of malondialdehyde compared to the control diet. In conclusion, dietary supplementation of lysolecithin could confer benefits of feed utilization, body composition and antioxidative capacity of channel catfish.     

Effect of Artemia enrichment on the growth and survival of Pacific bluefin tuna Thunnus orientalis (Temminck & Schlegel) larvae

This study was carried out to investigate the suitability of Artemia enriched with docosahexaenoic acid (DHA) and choline as live food on the growth and survival rate of the Pacific bluefin tuna (PBT; Thunnus orientalis) larvae. The PBT larvae were fed either Artemia enriched with oleic acid (Diet 1), DHA (Diet 2), DHA+choline 1.0 mg L^?1 (Diet 3) and DHA+choline 2.0 mg L^?1 (Diet 4) or striped knifejaw larvae (Diet 5, reference diet), in duplicate for 12 days. Enrichment of Artemia with DHA significantly increased the DHA levels to 13.9, 13.8 and 12.5 mg g^?1 on a dry matter basis in Diets 2, 3 and 4 respectively; however, the levels were significantly lower than the reference diet (26.9 mg g^?1 dry matter basis; Diet 5). Although growth and survival rate were significantly improved by the enrichment of Artemia with DHA and choline, the improvement was negligible compared with the enhanced growth and survival rate of the fish larvae‐fed group (P<0.05). The results demonstrated that enriched Artemia does not seem to be the right choice to feed the PBT larvae perhaps because of the difficulties in achieving the correct balance of fatty acid with higher DHA/EPA from Artemia nauplii.     

The effects of dietary Eucommia ulmoides Oliver on growth,feed utilization,antioxidant activity and immune responses of turbot (Scophthalmus maximus L.)

The present study was conducted to evaluate the effects of dietary Eucommia ulmoides (EU) on growth, feed utilization, antioxidant activity and immune responses of turbot fed a basal diet (CON) or EU‐supplemented diets with 5.0 g/kg (EU1), 10.0 g/kg (EU2) and 20.0 g/kg (EU3) EU leaf powder. After 70‐day trial, EU supplementation did not affect nutrient utilization, but reduced feed intake (FI) and specific growth rate (SGR) of fish at doses above 5.0 g/kg. Superoxide dismutase (SOD), catalase (CAT) and total antioxidant capacity (T‐AOC) activities in the EU‐supplemented groups were significantly higher than those in the control group at a dose of 20.0 g/kg. Significantly reduced malondialdehyde (MDA) contents were observed in EU‐supplemented groups at doses over 5.0 g/kg. Furthermore, fish fed 20.0 g/kg EU showed the highest lysozyme (LZM) activity among groups. The EU‐supplemented diets with doses above 5.0 g/kg significantly enhanced the mRNA expressions of cytokines. The expression level of major histocompatibility complex II alpha (MHC IIα) was significantly upregulated compared to that of the control fish when the supplemental level was at 20.0 g/kg. Taken together, the present study indicated that the EU could remarkably enhance the antioxidant activity, non‐specific immunity and maintain an active immune response in turbot.     

Fishmeal alternative from renewable CO2 for rainbow trout feed

The rapid global growth in fish farming and limited supply of fish meal (FM) has consequently reduced FM inclusion levels in compound feeds leading to a higher reliance on alternative protein sources. Sasya is a single cell protein (SCP) product that has a similar amino acid profile as FM. The aim of this study was to evaluate the effects of replacing FM with SCP on in vivo digestibility, growth, feed efficiency, whole‐body proximate/amino acid composition and gene expression levels of various hepatic enzymes in rainbow trout (Oncorhynchus mykiss). Three isonitrogenous (470 g/kg crude protein) and isolipidic (18 g/kg crude lipid) diets were formulated as follows: Diet 1: control (30% FM); Diet 2:24% FM + 6% SCP and Diet 3:18% FM + 12% SCP. Each diet was hand‐fed to triplicate tanks containing 30 rainbow trout fingerlings (4.99 ± 0.20 g) for 9 weeks. Apparent digestibility coefficients of SCP for dry matter, crude protein, lipid and energy were 60, 80, 93 and 74% respectively. Growth performance (final weight: 69–71 g), feed conversion ratios (0.91–0.94) as well as whole‐body protein and amino acid composition were unaffected by diets. However, Diet 3 significantly increased whole‐body crude fat and energy. Fish fed the SCP‐based diets had significantly higher expression for carnitine palmitoyltransferase‐1b (CPT1b), fatty acid delta 6 desaturase (FADS6) and fatty acid elongase 5 compared to the control. Overall, the quality of the SCP was similar as FM. Therefore, this product could enlarge the portfolio of alternative protein sources that can be used in fish diets and thus open a new market opportunity for use of a new feed resource in the feed industry.     

Dietary pantothenic acid requirement of fingerling Channa punctatus (Bloch) based on growth,feed conversion,liver pantothenic acid concentration and carcass composition

A 16‐week feeding trial was conducted to determine the dietary pantothenic acid requirement of fingerling Channa punctatus. Six casein–gelatin‐based diets (450 g/kg CP; 18.39 kJ/g GE) with graded levels of pantothenic acid (0, 10, 20, 30, 40 and 50 mg/kg diet) were fed to triplicate groups of fish (6.2 ± 0.71 cm; 4.26 ± 0.37 g) near to apparent satiation. The growth evaluation in terms of absolute weight gain (AWG), feed conversion ratio (FCR) and protein retention efficiency (PRE) indicated the best performance (p < .05) in fish fed diet containing 30 mg/kg pantothenic acid. Highest haemoglobin, haematocrit and RBCs counts were also obtained in fish fed diet with 30 mg/kg pantothenic acid. Mean cell haemoglobin and mean cell volume were found to be lowest in fish fed pantothenic acid‐free diet indicating the anaemia in this group of fish. Superoxidase dismutase and catalase activities of liver tissue were found to improve (p < .05) with the increasing levels of dietary pantothenic acid from 0 to 30 mg/kg. However, liver pantothenic acid concentration responded positively with the increasing levels of pantothenic acid up to 40 mg/kg diet and then stagnation in liver pantothenic acid concentration with the further inclusion of pantothenic acid was recorded. Second‐degree polynomial regression analysis of AWG, FCR and PRE exhibited the pantothenic acid requirement at 36.4, 32.8 and 34.7 mg/kg diet, respectively. Data generated during this study would be useful in formulating pantothenic acid‐balanced commercial feeds for the intensive culture of this fish.     

Dietary administration of astaxanthin improves feed utilization,growth performance and survival of Asian seabass,Lates calcarifer (Bloch, 1790)

This study was undertaken to assess the impacts of dietary astaxanthin supplementation on growth performance, feed utilization, survival, and serum growth hormone (GH) availability of Asian seabass, Lates calcarifer, with special reference to dose–response relationships and variations during different feeding phases (short‐term, medium‐term and long‐term). Fish were fed the following diets in triplicate for 90 days: the control (CD), AX50 (50 mg astaxanthin/kg diet), AX100 (100 mg astaxanthin/kg diet) and AX150 (150 mg astaxanthin/kg diet). The findings revealed that fish exhibited significant linear increments (p < .05) in specific growth rate (SGR), weight gain, feed utilization efficiency and survival when fed various diets with escalating levels of astaxanthin. Supplementation with dietary astaxanthin significantly augmented (p < .05) GH levels in fish. Significant positive associations (p < .05) were observed between circulating serum GH levels and SGR of fish from all groups following three consecutive feeding phases, denoting a robust cause‐and‐effect relationship. Circulating GH concentrations were considered as a sensitive biomarker of growth performance in Asian seabass. This study illustrated that supplemental astaxanthin could be administered in culture protocols to improve the growth rate and commercial hatchery production of Asian seabass, and possibly other teleost species.     

Effects of dietary chlorogenic acid on growth,flesh quality and serum biochemical indices of grass carp (Ctenopharyngodon idella)

The study was to investigate effects of dietary chlorogenic acid (CGA) on growth performance, flesh quality and serum biochemical indices of grass carp (95.1 ± 0.3 g) (Ctenopharyngodon idella) fed seven different diets, including control diet, Eucommia ulmoides (EU)‐supplemented diet (20 g kg^–1) and CGA‐supplemented diets containing 100, 200, 400, 600 and 800 mg/kg CGA. Contents of collagen and alkaline‐insoluble collagen in muscle and skin were significantly increased by dietary CGA and EU (p < .05). Total essential amino acids (TEAA) and total amino acids (TAA) in muscle of grass carp fed EU diet or 400, 600 and 800 mg/kg CGA diet were significantly higher than those of fish fed control diet and 100 and 200 mg/kg CGA diet (p < .05). Fish fed 200–800 mg/kg CGA showed significantly lower muscle crude lipid content than EU, control and 100 mg/kg CGA groups (p < .05). Fish fed CGA‐supplemented diets (100–800 mg/kg) had significantly higher muscle fibre density and lower muscle fibre diameter than control group (p < .05). In conclusion, supplementation of CGA improved flesh quality of grass carp, and supplemental level of CGA for improving flesh quality and growth was estimated to be 400 mg/kg diet.     

Comparative study on the effects of chelated or inorganic manganese in diets containing tricalcium phosphate and phytate on the growth performance and physiological responses of turbot Scophthalmus maximus

A growth trial was conducted to evaluate the effects of chelated (Mintrex^? Mn, Mn‐M) or inorganic (MnSO₄·H₂O, Mn‐S) manganese (Mn) on growth, feed utilization, tissue Mn deposition and liver superoxide dismutase (SOD) activity in turbot Scophthalmus maximus. A semi‐purified basal diet was formulated to be deficient in Mn (3.7 mg kg^?1) and contained tricalcium phosphate and sodium phytate at levels of 20 and 5 g kg^?1, respectively. Ten other diets were made by adding five levels (5, 10, 20, 35 and 55 mg Mn kg^?1 diet) of either the Mn‐M or Mn‐S to the basal diet, respectively. The 11 experimental diets were fed to groups of turbot (mean initial weight: 4.6 g) for 8 weeks. Results showed that the specific growth rate (SGR), feed intake, whole body Mn/vertebra Mn concentration and Mn‐SOD activity in liver were significantly improved by Mn supplementation (P < 0.05). On the basis of SGR, vertebra Mn concentration or liver Mn‐SOD activity data, dietary Mn requirement was estimated to be 10.5, 46.3 or 12.9 mg kg^?1 for turbot fed Mn‐S, and the same was estimated to be 7.6, 43.0 or 22.5 mg kg^?1 for turbot fed Mn‐M, respectively. There was no significant difference in growth, feed intake, whole body Mn concentration or vertebra Mn concentration between the two dietary Mn sources (P > 0.05).     

The optimum dietary isoleucine requirement of juvenile hybrid grouper (Epinephelus fuscoguttatus ♀ × Epinephelus lanceolatus ♂)

A six‐week growth trial was conducted to evaluate the optimum dietary isoleucine requirement of juvenile hybrid grouper (Epinephelus fuscoguttatus ♀ × Epinephelus lanceolatus ♂). Seven isoenergetic (3,400 kcal/kg of dry matter), isoproteic (496 g/kg of dry matter) and isolipidic (70 g/kg of dry matter) diets were formulated to contain graded Ile levels (7.3, 11.3, 15.7, 19.6, 23.5, 26.8 and 30.8 g/kg, dry‐matter basis). Each experimental diet was fed to triplicate groups of 12 hybrid grouper juveniles (average initial body weight: 6.00 ± 0.01 g/fish). Experimental fish were randomly distributed into 21 glass tanks (L 60 × W 45 × H 50 cm) connected to mechanical and biological water filters as a recycling system. Fish were fed twice daily (08:00 and 16:00) to apparent satiation. After the sampling of the growth trial, the remaining fish in each group were fed their corresponding diets for 2 d and then exposed to 4 mg Cu²⁺ · L^?1 water for 24 hr. Results showed that growth performance and feed utilization were significantly affected by different dietary Ile levels (p < .05). Weight gain percentage (WG%), protein productive value (PPV), protein efficiency ratio (PER) and feed efficiency (FE) were increased as dietary Ile level increased, reaching a peak value at 19.6 g/kg dietary Ile, and thereafter, these four parameters declined as dietary Ile level continued to increase. Daily feed intake (DFI) showed an opposite tendency of variations as FE. The quadratic regression analysis of WG%, PPV, PER and FE against dietary Ile levels indicated that the optimum dietary Ile requirement for hybrid grouper was estimated to be 19.8, 20.8, 19.4 and 19.1 g/kg dry matter, respectively. Among all experimental treatments, fish fed 19.6 g/kg dietary Ile had the highest expression of growth and protein synthesis‐related genes, including growth hormone (GH) in pituitary, insulin‐like growth factor 1 (IGF‐1), growth hormone receptor 1 (GHR1), target of rapamycin (TOR) and S6‐kinase 1 (S6K1) in liver. Gut micromorphology was significantly influenced by dietary Ile levels. After the exposure to 4 mg Cu²⁺ · L^?1 water for 24 hr, fish fed 19.6 g/kg dietary Ile had the highest survival and the best immunologic manifestation among all experimental treatments. Generally, the optimum dietary Ile requirement for maximum growth of hybrid grouper was estimated to be 19.8 g/kg dry matter, corresponding to 39.9 g/kg dietary protein.     

Effect of DL‐methionine supplementation on the success of almost total replacement of fish meal with soybean meal in diets for hybrid tilapia (Oreochromis niloticus × Oreochromis mossambicus)

This study evaluated the effects of increasing levels of methionine (Met) supplementation on the success of almost total replacement of fish meal (FM) with soybean meal (SBM) in diets for hybrid tilapia (Oreochromis niloticus × Oreochromis mossambicus). Fish were fed for 70 days a FM‐based diet (Diet1‐positive control) or SBM‐based diets supplemented with graded levels of DL‐methionine (Diet2 to Diet7). Contrast in dietary Met, concentration was created by supplementing Diet2‐negative control with 1.2 (Diet3), 2.4 (Diet4), 3.6 (Diet5), 4.8 (Diet6) or 6.0 g kg^?1 (Diet7) of DL‐Met. Specific growth rate (SGR), feed conversion ratio (FCR), and protein gain and retention efficiency (PER) improved significantly with increasing levels of dietary DL‐Met supplementation. Moreover, nonlinear regression analysis of the effects of supplementing SBM‐based diet with graded levels of DL‐Met indicated that a dietary Met + Cys level of 15.7 and 12.5 g kg^?1 diet (as fed) was required to reach 95% of maximum weight and protein gain, respectively. Supplementation of SBM‐based diet with graded levels of DL‐Met proved an effective strategy in reducing FM content in practical diets for hybrid tilapia. Data also indicate that adjustment of dietary formulas according to currently recommended Met or Met + Cys dietary concentrations is probably limiting maximum growth potential of hybrid tilapia.     

Effect of dietary chitosan oligosaccharide complex with Ce (IV) on growth,immunity and disease resistance against Vibrio splendidus of sea cucumber,Apostichopus japonicas

An 8‐week feeding trial was conducted to investigate the effects of dietary chitosan oligosaccharide complex with cerium (Ce IV) (COS‐Ce) on growth performance, nonspecific immunity and disease resistance of sea cucumber, Apostichopus japonicas. Five isonitrogenous (18.6%) and isolipidic (1.1%) practical diets were formulated with graded level of COS‐Ce (0, 150, 300, 600 and 1200 mg kg^?1 dry feed), which were named as COS‐Ce/0, COS‐Ce/150, COS‐Ce/300, COS‐Ce/600, COS‐Ce/1200 respectively. Each diet was allocated to four replicates of sea cucumbers (Initial weight: 6.72 ± 0.02 g). Sea cucumbers were fed to apparent satiation once daily (19:00 hours) for 56 days. During the experiment, water temperature was kept at 16 ± 0.5°C, pH 7.8–8.2, dissolved oxygen beyond 5 mg L^?1, ammonia nitrogen below 0.5 mg L^?1 and salinity from 30‰ to 31‰. Results showed that the specific growth rate of sea cucumbers was significantly higher in COS‐Ce/600 than that in other four treatments. Activities of phagocytosis, respiratory burst, acid phosphatase and alkaline phosphatase in COS‐Ce/600 were significantly higher than that in COS‐Ce/0 (P < 0.05) respectively. On the contrary, cumulative mortality was the lowest in COS‐Ce/600 following 14 days exposure to Vibrio splendidus (P < 0.05). In conclusion, these results confirmed that dietary COS‐Ce had beneficial effects on growth performance, nonspecific immunity and disease resistance of sea cucumber.     

Nutritional evaluation of distiller's dried grain with soluble as replacement to soybean meal in diets of milkfish,Chanos chanos and its effect on fish performance and intestinal morphology

A 90‐day feeding trial was conducted on milkfish, Chanos chanos with an initial mean body weight of 3.07 ± 0.17 g (mean ± standard error of mean). Six treatment diets were formulated to contain 0 g/kg (Diet 1), 150 g/kg (Diet 2), 25 g/kg (Diet 3), 300 g/kg (Diet 4), 350 g/kg (Diet 5) and 450 g/kg (Diet 6) distiller's dried grain with soluble (DDGS). All the dietary treatments were isonitrogenous (350 g/kg crude protein) and isolipidic (6% crude lipid). Result of the feeding trial indicated that growth rates, feed intake and feed efficiency were not significantly (p > .05) affected by inclusion levels of DDGS by up to 450 g/kg in the feed. Proximate body composition (crude protein, crude lipid, ash, fibre) in fish fed the dietary treatments were not significantly (p > .05) affected as well. The DDGS when used as a milkfish ingredient has a protein digestibility of 910 g/kg, fat disgetsibility of 850 g/kg, carbohydrate digestibility of 750 g/kg and a dry matter digestibility of 520 g/kg Results from the intestinal morphology displayed no apparent pathological changes in the digestive tract of fish fed all dietary treatments. These results indicate that DDGS can be efficiently utilized by milkfish by up to 450 g/kg without negatively affecting performance parameters and intestinal morphology.     

Effects of dietary vitamin C and vitamin E on the growth,antioxidant defence and digestive enzyme activities of juvenile discus fish (Symphysodon haraldi)

A 56‐day experiment was carried out to investigate the effects of dietary vitamin C and vitamin E on the growth, antioxidant status and digestive enzyme activities of discus fish (Symphysodon haraldi; initial body weight: 7.96 ± 0.61 g and body length: 5.45 ± 0.65 cm). Animals were fed with 13 different diets including one control diet and 12 treatment diets containing four levels of vitamin C (magnesium‐L‐ascorbyl‐2‐phosphate; 40, 80, 120 and 160 mg/kg) crossed with three levels of vitamin E (DL‐α‐tocopheryl acetate; 40, 80 and 120 mg/kg). The results showed that the fish fed diets containing additional vitamin C (40 mg/kg) and vitamin E (80 mg/kg) showed higher specific growth rate, length growth rate, total antioxidant capacity and protease activity but had lower feed conversion ratio and total superoxide dismutase activity than those fed the control diet. Collectively, these findings suggest that the inclusion of additional 40 mg/kg of vitamin C and 80 mg/kg of vitamin E in the basal diet could have beneficial effect on the growth, antioxidant defence and digestion of S. haraldi.