Effect of two choline sources on the performance of postlarval Marsupenaeus japonicus bate

The present study was conducted to clarify the effect and the interaction between two choline sources [choline chloride (CC) and soybean phosphatidylcholine (SPC)] on the performances of postlarval shrimp, Marsupenaeus japonicus. A 30‐day feeding experiment was conducted as a 2 × 2 factorial design. The postlarval shrimp were fed with four κ‐carrageenan micro‐bound diets that contained two levels of CC (0.6 and 1.2 g kg⁻¹) and two levels of SPC (20 and 40 g kg⁻¹). A significant (P < 0.05) interaction was also detected between both choline sources in terms of the weight gain, apparent feed efficiency ratio, apparent protein efficiency ratio and total lipid, free choline and phosphatidylcholine contents of the shrimp whole body except for survival, moisture, and protein contents of the whole body. At the lower dietary SPC (20 g kg⁻¹) level, increasing of CC level from 0.6 to 1.2 g kg⁻¹ significantly enhanced the above parameters, whereas such positive effect of dietary CC was diminished at the higher dietary SPC (40 g kg⁻¹) level. Standing on the different viewpoint, the effect of supplemental SPC was also affected with the dietary levels of CC.     

Effect of choline chloride as an osmoregulator as well as its role in growth and the biochemical content of postlarval kuruma shrimp; Marsupenaeus japonicus (Bate)

A 45‐day feeding experiment was conducted to examine two levels of dietary choline chloride (CC) [0.6 and 1.2 g kg^?1 CC] against control (0.0 g kg^?1 CC) on the biological, biochemical composition and stress tolerance of postlarval (PL‐20) Marsupenaeus japonicus. The results showed improvements in some biochemical contents such as phosphatidylcholine (PC) and methionine (Met) as 0.6 and 1.2 g kg^?1 dietary CC significantly (P < 0.05) increased both PC and Met contents of shrimp carcass more than those of the control group. The results also showed that supplemental (0.6 g kg^?1) choline could improve (P < 0.05) PC/PE (phosphatidylethanolamine) ratio. Growth parameters of the shrimp group that received 0.6/1.2 g kg^?1 dietary CC showed a significant (P < 0.05) improvement. In case of osmotic stress test, 0.6 g kg^?1 supplemented CC level showed significantly (P < 0.05) longer LT‐50 (the lethal time needed to kill half of the population) than the other shrimp groups that received 0.0 and 1.2 g kg^?1 dietary CC levels. This study showed the efficacy of 0.6 g kg^?1 dietary choline to improve the osmotic tolerance of kuruma shrimp as well as growth, survival and biochemical contents of postlarval kuruma shrimp.     

Effects of water-soluble and fat-soluble choline sources on the performances of juvenile kuruma shrimp, Marsupenaeus japonicus Bate

The present study was undertaken to clarify the effect and interaction of choline chloride (CC) and phosphatidylcholine (PC), the water‐ and fat‐soluble sources of choline, on the performances of kuruma shrimp, Marsupenaeus japonicus juveniles using as response variables such as percent weight gain (%WG), specific growth rate (SGR), survival (SR%), feed efficiency ratio (FER), protein efficiency ratio (PER), proximate composition, fatty acids profile and free choline and PC contents in the whole body of kuruma shrimp. A 40‐day feeding trial was conducted as a 2 × 3 factorial experiment with six test diets containing three levels of CC (0.3, 0.6 and 1.2 g kg^?1) and two levels of soybean PC (SPC; 2 and 4 g kg^?1). Both of the choline sources (CC and SPC) showed a significant interaction (P<0.05) regarding all the evaluated response variables except for the proximate and fatty acid contents. Interestingly, there was a positive effect (P<0.05) of CC observed with increasing its level at the low level of SPC and vice versa. However, the magnitudes of the beneficial effect of CC in terms of the evaluated parameters were changed with the different dietary levels of SPC. Also, the inclusion of higher levels of SPC (4 g kg^?1) or CC (0.6 and 1.2 g kg^?1) diminished the effect of the other source.     

Effects of DL‐methionine supplementation on the success of fish meal replacement by plant proteins in practical diets for juvenile gibel carp (Carassius auratus gibelio)

A ten‐week feeding trail was conducted to investigate the effects of increasing DL‐methionine (Met) supplementation on the success of fish meal (FM) replacement with plant proteins in practical diets for juvenile gibel carp, Carassius auratus gibelio. Twelve isoenergetic diets were formulated including two 150 g kg^?1 FM diets (Diet 1—positive control 1 reflecting a commercial diet and Diet 2—positive control 2 reflecting a commercial diet but with balanced essential amino acid (EAA) profile) and ten 50 g kg^?1 FM diets (negative controls) supplemented with graded levels (0–3.0 g kg^?1) of DL‐Met (Diets 3–12). Each diet was fed to triplicate groups of gibel carp, near satiation four times daily for 10 weeks. Diet 2 with balanced EAA profile produced better final weight, specific growth rate (SGR) and feed conversion ratio (FCR) than the negative control diet containing no supplemental Met (Diet 3), but did not significantly differ from Diet 1. However, DL‐Met supplementation (0.5–3.0 g kg^?1) in the negative control diets (Diets 4–12) produced growth performances similar to those fed the positive control diets (Diets 1 and 2). Based on quadratic regression analysis, the optimal dietary Met level with 5.2 g kg^?1 of dietary cysteine (Cys) was found to be 7.1 g kg^?1 dry diet for SGR and FCR. The corresponding total sulphur amino acid requirements (Met + Cys) of this species were calculated to be 12.3 g kg^?1 dry diet for SGR and FCR. DL‐Met supplementation in 50 g kg^?1 FM diets showed a decreasing trend in plasma cholesterol contents (p < .05). No significant differences were observed in whole‐body composition, plasma protein, triglyceride and free EAA contents among dietary treatments, while plasma aspartate transaminase, albumin and ammonia contents were significantly influenced by dietary Met levels. Juvenile gibel carp grew equally well on 150 g kg^?1 FM diet or 50 g kg^?1 FM diets balanced for EAA profile with supplemental amino acids. The results of this study overall indicate that balancing dietary amino acid levels with DL‐Met supplementation is a key strategy in successfully reducing FM levels in the diets of gibel carp.     

Fishmeal levels can be successfully reduced in white shrimp (Litopenaeus vannamei) if supplemented with DL‐Methionine (DL‐Met) or DL‐Methionyl‐DL‐Methionine (Met‐Met)

The main objective of this study was to evaluate the effect of methionine supplementation when reducing fishmeal levels in diets for white shrimp (Litopenaeus vannamei). Tested diets consisted of a positive control with 260 g/kg fishmeal (D1), two negative controls with 100 g/kg fishmeal and no amino acid (AA) supplementation (D2) or supplemented with lysine but not methionine (D3), and four additional diets with 100g/kg fishmeal supplemented with increasing levels of DL‐Met (1.0, 2.0 or 3.0 g/kg) (D4, D5, D6) or Met‐Met (1.0 g/kg) (D7). Each diet was fed to four groups of 30 shrimp for 8 weeks at a daily rate of 70 g/kg body weight. Reduction in fishmeal from 260 g/kg down to 100 g/kg did not significantly affect survival rate, feed conversion ratio (FCR), protein efficiency ratio (PER) or protein retention efficiency (PR%) of white shrimp. However, growth performance (final body weight, FBW; weight gain, WG; specific growth rate, SGR) was reduced when dietary fishmeal level was reduced from 260 g/kg (D1) to 100 g/kg without methionine supplementation (D2). The growth performance (FBW, WG and SGR) of shrimp was significantly increased by supplementation of the 100 g/kg fishmeal diet with increasing levels of DL‐Met (p < .05). Same performance as positive control (D1) was achieved with diets containing 100 g/kg fishmeal and supplemented with 3.0 g/kg DL‐Met or 1.0 g/kg Met‐Met. The highest values of growth performance (FBW, WG and SGR) were found in shrimp fed D6 and D7 diets, which were significantly higher than those of shrimp fed D2 and D3 diets (p < .05) but without statistical differences with shrimp fed D1, D4 and D5 diets (p > .05). The highest values of whole‐body and muscle protein contents were found in shrimp fed D1 diet, which were significantly higher than those of shrimp fed all other diets (p < .05). The highest value of intestinal tract proteolytic enzyme activity was found in shrimp fed Met‐Met‐supplemented diet (D7) and followed by the positive control diet (D1) and 3 g/kg DL‐Met‐supplemented diet (D6) (p < .05). The highest values of apparent digestibility coefficients (ADCs) of dry matter and crude protein were found in Met‐Met‐supplemented diet (D7) and followed by the positive control diet (D1) (p < .05). Shrimp fed the D1 diet showed the highest value of total essential amino acid (EAA) and was significantly higher than shrimp fed D2–D3 (p < .05) but without significant difference with shrimp fed D4–D7 (p > .05). In conclusion, results showed that same performance can be achieved with diets containing 260 or 100 g/kg fishmeal supplemented with 3.0 g/kg DL‐Met or 1.0 g/kg Met‐Met. Moreover, supplementation of limiting methionine in low‐fishmeal diets seems to improve the digestive proteolytic activity, improving digestibility of dry matter and protein, and eventually to promote growth of juvenile white shrimp in fishmeal reduction diets.     

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.     

Supplementation with 2‐hydroxy‐4‐(methylthio)butanoic acid (HMTBa) in low fish meal diets for the white shrimp,Litopenaeus vannamei

This work evaluated the performance of Litopenaeus vannamei to low fish meal diets supplemented with 2‐hydroxy‐4‐(methylthio)butanoic acid (HMTBa). A basal diet with 150.0 g kg^?1 of anchovy fish meal was designed. Two positive control diets were formulated to reduce fish meal at 50% and 100% with 1.0 and 2.0 g kg^?1 of MERA? Met_Ca (calcium salt with 84% HMTBa activity), respectively. Two nearly equivalent diets acted as negative controls, without HMTBa supplementation. A total of 50 clear‐water tanks of 500 L were stocked with 2.22 ± 0.19 g shrimp under 70 animals m^?2. Shrimp survival (92.3 ± 5.1% and 81.4 ± 8.0%), yield (808 ± 12 and 946 ± 17 g m^?2) and FCR (2.17 ± 0.19 and 3.12 ± 0.37) showed no differences among diets after 72 or 96 days, respectively. A significantly higher shrimp body weight and weekly growth were observed for those fed with the basal diet or diets supplemented with HMTBa compared with non‐supplemented ones. This study has shown that L. vannamei growth, body weight, survival, yield and FCR were supported by HMTBa supplementation when 150.0 g kg^?1 of fish meal was replaced by soybean meal and other ingredients, at 50% and 100%.     

Physiological, metabolic and haematological responses in white shrimp Litopenaeus vannamei (Boone) juveniles fed diets supplemented with astaxanthin acclimated to low-salinity water

The effects of dietary astaxanthin supplemented at 0, 40, 80 or 150 mg astaxanthin kg⁻¹ on growth, survival, moult frequency, osmoregulatory capacity (OC) and selected metabolic and haematological variables in Litopenaeus vannamei acclimated to low‐salinity water (3 g L⁻¹) were evaluated. Supplemented astaxanthin at 80 mg kg⁻¹ improved growth, survival and moult frequency in shrimp. The lowest OC was also exhibited in shrimp fed with dietary astaxanthin at 80 mg kg⁻¹. Shrimp haemolymph concentrations of glucose, lactate, haemocyanin and total haemocyte count were all significantly enhanced by feeding the diet supplemented with 80 mg astaxanthin kg⁻¹ compared with shrimp fed with the other diets. On the basis of these results, dietary astaxanthin supplementation of 80 mg kg⁻¹ is recommended for juvenile L. vannamei cultured in low‐salinity water.     

Effects of supplementing bioactive compounds to a formulated diet on sensory compounds and growth of shrimp,Litopenaeus vannamei (Boone, 1931)

Experimental diets were processed at the Oceanic Institute by adding various bioactive compounds (lutein, fucoxanthin, astaxanthins (Ax), glucosamine, carotenoid mix, phytosterol mix, bromophenol (Bp) mix or their combination) to a formulated (control) diet to examine their effects on sensory composition and growth of shrimp. These diets and a commercial feed were fed to ～1.6 g shrimp (Litopenaeus vannamei) in four replicates in an indoor laboratory under flow‐through conditions for 8 weeks. Results indicated that all the supplementations of the bioactive compounds did not improve shrimp growth (0.79–0.97 g week^?1) compared with that (0.94 g week^?1) of the control diet (P>0.05). However, inclusion of lutein (200 mg kg^?1) or carotenoid mix (827 mg kg^?1) in the control diet (with supplemental Ax) resulted in much higher free Ax (48.3 or 46.5 mg kg^?1) and esterified Ax (6.2 or 3.9 mg kg^?1) content in shrimp tails than the control diet (28.4; 1.4 mg kg^?1 respectively) (P<0.05). Inclusion of Bp (2 mg kg^?1) in the control diet resulted in higher levels of Bp (160 μg kg^?1) in shrimp tail muscle than the control diet (81 μg kg^?1) (P<0.05). Three free amino acids, glycine, proline and alanine might be mainly responsible for the sweet taste of L. vannamei. The results suggest that the supplementation of the bioactive compounds may not affect shrimp growth performance, but some may affect the composition and taste of shrimp.     

Assessment of dietary lecithin and cholesterol requirements of mud crab, Scylla serrata, megalopa using semi-purified microbound diets

The effects of varying dietary lecithin and cholesterol levels on growth, development and survival of mud crab, Scylla serrata, megalopa were evaluated using six semi‐purified, microbound diets formulated to be iso‐energetic and containing three levels of supplemental lecithin (0, 20 and 40 g kg⁻¹ diet dry weight) and two levels of supplemental cholesterol (0 and 7 g kg⁻¹ diet dry weight). Fifteen megalopa were reared individually in each treatment and the nutritional value of diets was assessed on basis of mean dry weight and mean carapace width of newly settled first crab stage, as well as development time to the first crab stage and overall survival. A significant interaction between supplemental dietary lecithin and supplemental dietary cholesterol was found for final mean dry weight of newly settled crabs, and highest survival (60%) was recorded for megalopa fed diets containing the highest levels of dietary lecithin (39.7–44.1 g kg⁻¹) (diet 5 and 6) regardless of whether diets were supplemented with cholesterol; this rate of survival was identical to that of megalopa fed live Artemia nauplii. The results indicate that supplemental dietary cholesterol may not be essential for mud crab megalopa when fed diets containing sufficient levels of supplemental dietary phospholipids.     

The effect of dietary taurine supplementation on growth performance,feed utilization and taurine contents in tissues of juvenile white shrimp (Litopenaeus vannamei,Boone, 1931) fed with low‐fishmeal diets

An 8‐week feeding trial was conducted to investigate the effects of different taurine levels on the growth performance of juvenile white shrimp fed with low‐fishmeal diets. Six level diets of dietary taurine were prepared by the supplementation of taurine (0, 0.4 g kg^?1, 0.8 g kg^?1, 1.2 g kg^?1, 2.0 g kg^?1 and 4.0 g kg^?1) to a control diet (100 g kg^?1 fish meal). Each diet was randomly assigned to triplicate groups of 30 shrimps (0.48 ± 0.0 g), each three times daily. Shrimp fed the 0.4 g kg^?1 and 0.8 g kg^?1 taurine‐supplemented diets, showed significantly higher weight gain, protein efficiency ratio and protein retention efficiency than those of shrimp fed the other diets. The quadratic regression analysis (y = ?55.59x² + 187.1x + 750.2 R² = 0.587) indicated that a maximum weight gain occurring at 1.68 g kg^?1 of taurine level. The whole body and hepatopancreas taurine contents of the taurine‐supplemented diets were on the same level and higher than those of the control group. Total free amino acid content in the hepatopancreas was significantly affected by taurine supplementation. The results of the present study demonstrate that the white shrimps require taurine as an essential nutrient for growth performance.     

Effects of replacing fish meal with poultry by‐product meal and soybean meal and reduced protein level on the performance and immune status of pond‐grown sunshine bass (Morone chrysops × M. saxatilis)

Two primary ways to achieve low‐cost, nutritionally efficacious diets for sunshine bass (Morone chrysops × M. saxatilis) are to decrease crude protein (CP) levels and the use alternative animal or plant ingredients to partially, or totally, replace fish meal. A 459‐day feeding trial was conducted with juvenile (35 g) sunshine bass to evaluate growth, feed efficiency, size distribution at harvest, immune function status and body composition when fed diets containing soybean meal (SBM), feed‐grade poultry by‐product meal (PBM), and supplemental methionine as complete replacements for menhaden fish meal (MFM) at 300 g kg^?1 diet, while simultaneously reducing dietary crude protein (CP; 320, 360, and 400 g kg^?1). The feeding trial was conducted in 12, 0.04‐ha earthen ponds stocked at a rate of 300 per pond (3000/ac). At 400 g kg^?1 dietary protein, there were no differences in responses between fish fed the diet containing MFM or the diet in which MFM was completely replaced with PBM and supplemental methionine on a digestible protein basis. However, final mean weight, percentage weight gain, specific growth rate, and protein efficiency ratio were linearly related (P < 0.10) to dietary protein level in the diets while no significant differences were found in feed intake and feed conversion ratio. The expected odds of fish at harvest being classified into larger size categories (> 680 g) decreased as dietary protein level decreased based on ordinal logistic regression. There were no significant relationships between body compositional indices and dietary treatments. Body fat ranged from 56 g kg^?1 to 62 g kg^?1, single fillets ranged from 28% to 30%, and livers ranged from 2.45% to 2.62% of body weight across treatments. Fillet protein concentration was positively linear and quadratic for protein level in the diet but fillet moisture, lipid and ash did not differ among diets. Total serum protein, immunoglobulin and lysozyme activity decreased linearly with decreasing diet protein level. These results suggest that complete replacement of MFM with feed grade PBM and supplemental methionine is possible in diets for sunshine bass and that further reductions in dietary protein level may be possible with amino acid supplementation.     

The effect of dietary methionine concentrations on growth performance of juvenile Nile tilapia (Oreochromis niloticus) fed diets with two different digestible energy levels

A growth trial was conducted to examine the effect of dietary digestible energy (DE) content on methionine (Met) utilization and requirement in juvenile Nile tilapia (Oreochromis niloticus). Ten iso‐nitrogenous (288 g kg^?1 protein) practical diets, with two DE levels (10.9 MJ kg^?1; 12.4 MJ kg^?1) and five methionine supplementation levels (0, 1, 2, 4 and 6 g kg^?1), were hand‐fed twice daily to triplicate groups of Nile tilapia (initial body weight 8.95 ± 0.06 g) for 8 weeks. Weight gain (WG) and specific growth rate (SGR) increased significantly with increasing dietary methionine concentration at the same DE content (P < 0.001). At the same dietary methionine level, WG and SGR of fish fed high‐DE diets were significantly higher than that of fish fed low‐DE diets (P = 0.0001), although no interaction was found between dietary DE and methionine supplementation. Based on quadratic regression analysis between dietary methionine concentration and weight gain, optimal methionine requirement for maximum growth, expressed as g Met required kg^?1 diet (low‐ versus high‐DE diets), increased as diet DE concentration increased (7.34 versus 9.90 g kg^?1 diet, respectively; with cysteine 4.70 g kg^?1 diet). The results indicated that diet DE content affects methionine utilization and requirement in juvenile Nile tilapia, fish fed high‐DE diets required more methionine for maximum growth.     

Effects of dietary dl‐methionyl‐dl‐methionine (Met‐Met) on growth performance,body composition and haematological parameters of white shrimp (Litopenaeus vannamei) fed with plant protein–based diets

A 10‐week feeding trial was conducted to evaluate the effects of supplementing different levels of dl ‐methionyl‐dl ‐methionine (AQUAVI^® Met‐Met) in plant protein–based diets on Litopenaeus vannamei. The positive control (PC) and negative control (NC) diets were designed with 20% and 8% fishmeal respectively, and other six diets were formulated with graded levels of Met‐Met from 0.05% to 0.30% with a 0.05% increment on the basis of NC diet (MM 0.05–MM 0.3). Six replicates were randomly assigned to each diet with 50 shrimp each having initial weight of 0.98 ± 0.02 g. The variation of FM concentration from 20% to 8% and supplemented with graded levels of Met‐Met did not affect the survival rate, feed conversion ratio, protein efficiency ratio, whole body and muscle proximate compositions (p > 0.05). However, diets with ≤0.20% Met‐Met supplementation resulted in significantly increased weight gain and specific growth rate, after which both parameters reached plateau. Shrimp fed the NC diet showed significantly lower total essential amino acid (EAA) content in muscle (p < 0.05). Supplementation of Met‐Met significantly improved apparent digestibility coefficients of dry matter, crude protein, lipid, phosphorus and EAAs (p < 0.05). Based on broken‐line analysis, the methionine requirement for white shrimp was estimated to be 0.87% when using Met‐Met as methionine source.     

Comparative study on the utilization of crystalline methionine and methionine hydroxy analogue calcium by Pacific white shrimp (Litopenaeus vannamei Boone)

The objective of this study was to compare the supplemental effects of crystalline DL‐methionine (DL‐Met) and methionine hydroxy analogue calcium (MHA‐Ca) on growth performance of Pacific white shrimp. Eight isoproteinic (355.3 ± 2.0 g/kg diet) and isolipidic (70.0 ± 2.2 g/kg diet) diets were prepared as positive diet (20% fish meal), negative diet (15% fish meal) and DL‐Met, MHA‐Ca‐supplemented diets with the supplementation of 0.03%, 0.06%, 0.09% DL‐Met and 0.04%, 0.07%, 0.1% MHA‐Ca in negative diet respectively. Pacific white shrimp (0.92 ± 0.03 g) were fed one of the eight diets for 49 days. The results showed that dietary DL‐Met did not affect weight gain (WG) and feed conversion ratio (FCR) (p > 0.05), but the supplementation of 0.1% MHA‐Ca significantly increased WG, protein and lipid retention, and reduced FCR (p < 0.05) when compared to the negative group, and reached the similar levels as the positive control. The total free amino acids (TFAA) in haemolymph of MHA‐Ca groups and PC, NC group peaked at the 3rd hr after feeding, but the peaking time of DL‐Met groups was advanced to the 2nd hr. Activities of aspartate aminotransferase (AST) and alanine aminotransferase (ALT) in haemolymph of all MHA‐Ca groups peaked at the 2nd hr, but DL‐Met groups peaked at the 1st hr after feeding. The above results indicated that the supplementation of 0.1% MHA‐Ca in a low fish meal diet could improve the growth performance and feed utilization of Pacific white shrimp, but dietary DL‐Met did not significantly affect the growth.     

Use of marine by‐product meals in diets for juvenile longfin yellowtail Seriola rivoliana

A 60‐day feeding trial to determine the nutritional value of marine by‐product meals in diets for longfin yellowtail Seriola rivoliana juveniles (48.1 ± 0.6 g initial weight) was conducted. Five diets were evaluated: a reference diet (RD; 500 g kg^?1 CP, 130 g kg^?1 L), containing 500 g kg^?1 of fish meal (FM); three experimental diets with 125 g kg^?1 of shrimp head (SM), Catarina scallop viscera (CM) or Pen shell viscera (PM) meals; and one diet (SCP) containing 125 g kg^?1 of each of the experimental meals, to partially replace FM. Survival was not significantly affected by any treatment. Individual weight gain per day was high for the PM (5.3 ± 0.51 g d^?1) and SM (4.7 ± 0.32 g d^?1) diets, being significantly higher than the RD (3.5 ± 0.23 g d^?1) and the other treatments (<1.2 g d^?1). Feed intake was high in PM and SM diets, and very low in SCP and CM diets. Biochemical and haematological parameters were similar among treatments RD, PM and SM, while fish fed CM and SCP exhibited lower levels of total protein, cholesterol, haematocrit and haemoglobin. The results indicate that SM or PM can be used to partially replace FM in diets for yellowtail juveniles.     

Effects of lysine and methionine supplementation on growth,body composition and digestive function of grass carp (Ctenopharyngodon idella) fed plant protein diets using high‐level canola meal

A 76‐day feeding trial was carried out to evaluate the effects of Lysine and Methionine supplementation on growth and digestive capacity of grass carp (Ctenopharyngodon idella) fed plant protein diets using high‐level canola meal (CM). Fish with initial average weight 103.9 ± 0.6 g were fed three extruded diets. Fish meal (FM) diet was formulated as the normal control with 40 g kg^?1 FM and 300 g kg^?1 CM; CM diet was prepared by replacing all FM with CM (total 340 g kg^?1) without Lys or Met supplementation; CM supplement (CMS) diet was similar to CM diet but was supplemented with essential amino acids (EAA) to ensure the levels of Lys and Met similar to those in the FM diet. Feed intake, feed efficiency and specific growth rate of the grass carp fed CMS and FM diets were similar (P > 0.05), but higher than those of the grass carp fed CM diet (P < 0.05). The hepatosomatic index, relative gut length, intestosomatic index and intestinal folds height were significantly improved in fish fed FM and CMS diets as compared to CM diet (P < 0.05). Lower activities of trypsin, lipase and amylase in hepatopancreas were observed in fish fed CM diet (P < 0.05). Three hundred and forty gram per kilogram CM without Lys or Met supplementation significantly decreased trypsin, lipase and amylase mRNA levels in hepatopancreas (P < 0.05). These results indicated that the high supply of CM (340 g kg^?1) in plant protein (200 g kg^?1 soybean meal and 100 g kg^?1 cottonseed meal) diets decreased digestive ability through decreasing digestive enzyme activities and enzyme gene's expressions of grass carp, and these side effects can be reversed by supplementing Lys and Met. Therefore, CM could be high level used in a plant protein blend‐based extruded diet for grass carp as long as EAA were supplemented.     

Digestibility and performance of pacu (Piaractus mesopotamicus) juveniles — fed diets containing different protein, lipid and carbohydrate levels

Due to lack of information on the use of non‐protein energy sources in diets for pacu (Piaractus mesopotamicus), a 2 × 2 × 3 factorial experiment was conducted to evaluate the performance and digestibility of 12 diets containing approximately two crude protein (CP; 220 and 250 g kg⁻¹), two lipid (40 and 80 g kg⁻¹) and three carbohydrate levels (410, 460 and 500 g kg⁻¹). The pacu juveniles‐fed diets containing 220 g kg⁻¹ CP did not respond (P > 0.05) to increased dietary lipid and carbohydrate levels, but the fish‐fed diets containing 250 g kg⁻¹ CP showed a better feed conversion ratio. There were interactions in weight gain (WG), specific growth rate (SGR), crude protein intake (CPI) and feed conversion rate (FCR) dependent on dietary carbohydrate and lipid levels, showing positive effects of increasing carbohydrate levels only for fish‐fed diets containing 80 g kg⁻¹ lipid level. However, when the diets contained 40 g kg⁻¹ lipid, the best energy productive value (EPV) results were obtained at 460 g kg⁻¹ carbohydrate. A higher usage of lipids (80 g kg⁻¹) reduced CPI and was detrimental to protein [apparent digestibility coefficient (ADC)_CP] and energy (ADC_GE), but did not affect growth. The ADC_GE improved proportionally as dietary carbohydrate levels increased (P < 0.05), increasing the concentration of digestible energy. In addition, the WG, CPI, ADC_GE results showed best use of the energy from carbohydrates when dietary protein level was 250 g kg⁻¹ CP. The utilization of 250 g kg⁻¹ CP in feeds for juvenile pacu for optimal growth is suggested. Therefore, the optimum dietary lipid and carbohydrate levels depend on their combinations. It can be stated that pacu uses carbohydrates as effectively as lipids in the maximization of protein usage, as long as it is not lower than 250 g kg⁻¹ CP or approximately 230 g kg⁻¹ digestible protein.     

Single or combined effects of fructo‐ and mannan oligosaccharide supplements and Bacillus clausii on the growth,feed utilization,body composition,digestive enzyme activity,innate immune response and lipid metabolism of the Japanese flounder Paralichthys olivaceus

In this study, we examined the effects of the following eight experimental diets, which varied in fructo oligosaccharides (FOS), mannan oligosaccharides (MOS) and Bacillus clausii concentrations, on the Japanese flounder: control diet (no FOS, MOS and B. clausii), diet F (5 g kg⁻¹ FOS), diet M (5 g kg⁻¹ MOS), diet FM (2.5 g kg⁻¹ FOS + 2.5 g kg⁻¹ MOS), diet B (10⁷ cells g⁻¹B. clausii), diet FB (5 g kg⁻¹ FOS + 10⁷ cells g⁻¹B. clausii), diet MB (5 g kg⁻¹ MOS + 10⁷ cells g⁻¹B. clausii) and diet FMB (2.5 g kg⁻¹ FOS + 2.5 g kg⁻¹ MOS + 10⁷ cells g⁻¹B. clausii). Japanese flounder, initially weighing an average of 21 g, were distributed into 24 net cages at a stocking density of 20 fish per cage. Each diet was hand‐fed to three groups of fish twice daily for 56 days. The weight gain rate (WGR) in fish fed diets B, MB and FMB were significantly higher than in fish fed the control diet, where the fish fed diet FMB had the highest WGR. Fish fed any of the diets, except diets F and B, exhibited better feed conversion ratio than those fed the control diet. Diets MB and FMB significantly elevated intestinal protease activity compared with the control diet, but only the diet FMB promoted amylase activity. Feeding diets FB and FMB increased body protein deposition; additionally, feeding diets B, MB and FMB significantly reduced body lipid deposition. Lysozyme (LSZ) activity was significantly higher in fish fed diets B, FB, MB and FMB than in fish fed the control diet. All diets, except diet M, decreased triglyceride (TG) levels compared to the control diet. Low‐density lipoprotein cholesterol levels in fish fed diets F, FB and FMB were significantly lower than in fish fed the control diet. Without exception, no diets affected feeding rate, condition factor, body moisture, ash contents, phagocytic activity of leucocytes or cholesterol or high‐density lipoprotein cholesterol levels. Our results suggest that diets supplemented with FOS, MOS and B. clausii improved growth performance and health benefits of the Japanese flounder more than other diets or the control diet.     

Effects of dietary choline supplementation on growth performance,lipid deposition and intestinal enzyme activities of blunt snout bream Megalobrama amblycephal fed high‐lipid diet

This study aimed to investigate the effects of dietary choline supplementation on growth, lipid deposition and intestinal enzyme activities of Megalobrama amblycephala. Fish were fed four diets with two lipid levels (50 and 150 g kg^?1) and two choline supplementations (600 and 1600 mg kg^?1) for 8 weeks. Feed conversion ratio (FCR), viscerosomatic index (VSI), hepatosomatic index (HSI), intraperitoneal fat (IPF) ratio, whole‐body and muscle lipid contents, intestinal lipase activities and lipoprotein lipase (LPL) activities all increased significantly (P < 0.05) as lipid levels increased, whereas the opposite was true for whole‐body and muscle moisture contents and intestinal amylase activities. VSI, IPF ratio and whole‐body lipid contents all decreased significantly (P < 0.05) with increasing dietary choline supplementations. Weight gain, muscle moisture content all increased significantly (P < 0.05) with increasing dietary choline supplementations when dietary lipid levels reached 150 g kg^?1, whereas the opposite was true for FCR, IPF ratio, IPF and liver LPL activities. In addition, abnormal hepatocytes were found in the liver of fish fed 150 g kg^?1 lipid with 600 mg kg^?1 choline supplementation. The result of this study indicated that extra choline supplementation can improve growth performance, intestinal enzymes activities and reduce excessive lipid deposition of M. amblycephala fed high lipid.