Periodical changes of plasma free amino acid levels and feed digesta in yellowtail after feeding non-fishmeal diets with or without supplemental crystalline amino acids

ABSTRACT: Postprandial changes of free amino acid (FAA) concentrations in plasma and feed digesta contents were examined in yellowtail, Seriola quinqueradiata (220–280 g bodyweight) fed non-fishmeal diets either with or without supplemental crystalline amino acids (lysine, methionine, threonine, and tryptophan) in order to evaluate the availability of supplemental amino acids. Non-fishmeal diets containing 30% soy protein concentrate as the major protein source were prepared in three diet forms: soft dry pellet, extruded pellet, and single moist pellet. The level of plasma FAA and feed digesta content were determined at 0, 3, 6, 9, 12, 18, and 24 h after feeding. Plasma levels of four supplemental amino acids in fish fed the non-fishmeal diets with EAA were higher than those of fish fed diets without EAA, suggesting that yellowtail can efficiently absorb supplemental crystalline amino acids irrespective of diet form. However, a remarkable difference was observed in the periodical patterns of these four amino acids between FAA derived from supplements and those from feed protein. Moreover, FAA patterns in fish fed the non-fishmeal diets with EAA were different from those of the control fishmeal diet. Of note, methionine concentration was markedly high during the whole experimental period, resulting in an amino acid imbalance that may have caused lower feed performances in fish fed the non-fishmeal diets with EAA compared to the control fishmeal diet.     

The problem of meeting dietary protein requirements in intensive aquaculture of marine fish larvae, with emphasis on Atlantic halibut (Hippoglossus hippoglossus L.)

Atlantic halibut (Hippoglossus hippoglossus) achieve a mature gastrointestinal tract approximately 2 months after first feeding (12 °C). The immature digestion may be the reason that compound diets fail to sustain growth and survival in first feeding halibut larvae and in larvae of other marine fish species. On the other hand, larvae fed with live feeds are capable of extraction of sufficient quantities of nutrients to sustain high growth rates. A lower availability of the protein in formulated diets compared with live prey is considered to be an important reason for the low performance of formulated diets. One approach to increase dietary protein availability is supplementation of pre‐digested proteins. Experiments using tube fed individual larvae show that halibut larvae are able to utilize hydrolysed protein more efficiently than intact protein. However, Atlantic halibut in culture did not respond well to dietary supplementation of hydrolysed protein, in contrast to some other species. One reason may be extensive leaching of pre‐hydrolysed proteins from the microparticulate feed. Atlantic halibut are slow feeders and may thus suffer more from nutrient leaching than species eating more rapidly. Feed formulation techniques affect dietary protein leaching, and in this paper, different techniques and their impact on feed properties are described. Microbound diets are most widely used in larval rearing, but show high rates of nutrient leaching. Lipid‐based capsules seem to have the best potential to prevent leaching, however, they are not able to deliver a complete diet. The high need for improvements in larval feed formulation techniques are clearly stated, and some suggestions are given. Among these are production of complex particles, where small lipid‐based capsules or liposomes containing the low molecular weight water‐soluble nutrients are embedded. In such feed particles the water‐soluble molecules are protected from leaching. Techniques for delivery of water‐soluble nutrients that are needed in large quantities, i.e. free amino acids or hydrolysed and water‐soluble protein, remain to be developed.     

Evaluation of hydrolysed rubber seed meal as a dietary protein source for Nile tilapia Oreochromis niloticus L.

This study evaluated the use of hydrolysed rubber seed meal as a locally grown alternative feed ingredient to reduce the use of fishmeal within formulated feeds for tilapia. Five experimental diets were prepared by formulating different inclusion levels of hydrolysed rubber seed meal (0%, 25%, 50%, 75% and 100% of plant‐based protein contribution). Dried and defatted rubber seed meal was hydrolysed by adding rumen digesta liquid to the ingredient. For digestibility measurement, chromic oxide was added to each diet as an inert marker. The digestibility trial was conducted over a 14‐day period by collecting faecal matter from the rearing tanks. In addition, a growth trial was conducted over a period of 50 days using four replicates per dietary treatment. In both experiments, all fish were fed three times daily to apparent satiation. At the end of growth trial, the inclusion level of hydrolysed rubber seed meal up to 50% of plant‐based protein contribution did not give any significant difference compared to the control diet in terms of feed efficiency, specific growth rate and protein retention parameters. In the digestibility study, fish fed diets containing hydrolysed rubber seed meal up to a 50% of plant‐based protein inclusion level did not give any significant difference compared to the control diet in terms of protein and dry matter apparent digestibility. Based on the result of this growth and digestibility study, up to a 50% of plant‐based protein contribution of hydrolysed rubber seed meal can be used within formulated tilapia feeds without any adverse effect.     

Digestibility and growth performance of juvenile rainbow trout (Oncorhynchus mykiss) fed with pea and canola products

A digestibility experiment and subsequent 84-day feeding experiment evaluated the use of pea and canola meal products in diets for rainbow trout. The effect of milling and heat treatment on nutrient, dry matter and energy digestibility of raw/whole peas, raw/dehulled peas, extruded/dehulled peas and autoclaved air-classified pea protein was determined. Digestibility of the protein component was uniformly high for all pea ingredients (90.9–94.6%), regardless of the processing treatment. Autoclaving or extrusion increased starch digestibility by 41–75% ( P  ≤ 0.05), which consequently increased energy and dry matter digestibility of whole and dehulled peas. Autoclaved air-classified pea protein had superior protein (94.6%), energy (87.0%) and dry matter (84.0%) digestibility ( P  ≤ 0.05). It was demonstrated that inclusion of 25% dehulled peas, 20% air-classified pea protein or 20% canola meal fines was feasible in trout diets allowing for replacement of soya bean meal. The data showed no difference ( P  ≥ 0.05) in feed intake, final weight and specific growth rate (SGR) measurements, and feed utilization was not compromised with inclusion of pea or canola meal products as the primary plant ingredient. It was concluded that dehulled peas, air-classified pea protein and canola meal fines are suitable ingredients for use in trout diet formulation at a level of 20%.     

Apparent digestibility of crude protein and apparent availability of individual amino acids in tilapia (Oreochromis niloticus) fed phytase pretreated soybean meal diets

Soybeans contain phytates, the anionic forms of 1,2,3,5/4,6-hexakis (dihydrogen phosphate) myoinositol, with the potential to reduce amino acid (AA) availability. Tilapia lack the intestinal enzyme phytase to hydrolyze phytates. Oreochromis niloticus (approximately 68 g) were fed diets containing either phytase pretreated or untreated soybean meal (SBM) incorporated at 0, 25, 50, 75, or 100% of the crude protein (CP) in a 33% CP diet to determine whether phytates reduce CP digestibility and AA availability. There were no differences in apparent CP digestibility. Dietary and available methionine (Met), and available lysine (Lys), decreased with increasing incorporation of phytase pretreated SBM. Reduced availability of Met and Lys from the phytase pretreated diets was likely due to removal of phytates. Phytates may reduce the effect of other antinutritional factors, protect amino acids from degradation, or decrease leaching of water soluble components. This revised version was published online in August 2006 with corrections to the Cover Date.     

Evaluation of feed protein quality by measuring plasma free amino acids in Atlantic salmon (Salmo salar L.) after dorsal aorta cannulation

Two successive experiments were conducted in order to assess plasma free amino acid (FAA) profiles as a method for evaluating protein quality of fish feeds for Atlantic salmon, Salmo salar (L.). In experiment 1, the importance of meal size and inter‐fish variation was assessed by using dorsal aorta cannulated fish and diets that contained different sources of fishmeal (menhaden versus herring) which in the case of herring, had been dried at either 70 or 100 °C. In experiment 2, an attempt was made to mimic a production situation by comparing the FAA profiles in salmon fed diets containing two commercially available fishmeals that had been produced in accordance with industrial standards (Norse‐LT94® and NorSeaMink®; Norsildmel AL, Fyllingsdalen, Norway). FAA profiles in plasma 6 h after feeding were compared with feed true protein digestibility as determined in mink. Cannulated fish, held in individual tanks, were hand‐fed twice daily to pellet rejection (satiety) and daily records of the actual rations consumed were maintained. A total of 24 different amino acids and other amino‐containing compounds were detected using high‐pressure liquid chromatography. Morning and evening meal size showed significant correlations. Meal size had a significant effect on blood levels of the majority of essential free amino acids (EAA) as well as the total sum of FAA (TFAA). In experiment 1, a marked inter‐individual effect was found, possibly because of incipient sexual maturation. FAA profiles were therefore corrected for meal size by linear regression while repeated sampling via the permanently implanted cannula allowed paired comparisons of the different test diets, minimizing inter‐individual variation. Significant differences in plasma FAA profile, EAA and TFAA were detected between fish fed all diets in both experiments. The preceding parameters for fish ingesting each feed were directly related to their respective mink protein digestibility in experiment 1, but not in experiment 2. Our results show that dietary protein quality can be differentiated by the aforementioned protocol, and by using fish with a low metabolic rate feed qualities could be ranked correctly as in experiment 1.     

Apparent digestibility of protein, energy, and amino acids in some selected feed ingredients for pacu Piaractus mesopotamicus

The apparent digestibility coefficients (ADCs) of amino acids (AA), protein, and energy in six feed ingredients (Brazilian fish meal, soybean meal, corn gluten meal, alcoholic yeast, corn, and wheat bran) we evaluated for pacu juveniles. In general, all ingredients showed high digestibility values for all AA, and differences among ADCs of individual amino acid were detected ( P  < 0.01). Corn gluten, soybean, and fish meals had the highest ADCs of AA. The ADCs of protein in fish meal, yeast, and corn gluten meal should not be used as AA digestibility indicators, because those showed differences up to 6.7% between the ADCs of protein and AA. All ingredients had lower ADCs of energy than corn gluten meal ( P  < 0.01). Lysine was the first limiting amino acid in fish meal, corn gluten meal, wheat bran, and corn, and the second limiting amino acid in soybean meal, as methionine was the first limiting amino acid in soybean meal and yeast. However, the soybean meal was the best quality protein source, as it had the highest digestible essential amino acid index. This demonstrated that digestible amino acid values can be used to formulate practical diets for pacu, preventing potential deficiencies or excess that might cause environmental and economic losses.     

Growth and protein utilization in Atlantic salmon (Salmo salar L.) given a protease inhibitor in the diet

In a series of experiments the effects of dietary protease inhibitor inclusions on growth and amino acid absorption rate were investigated in Atlantic salmon ( Salmo salar L.). An optimal inclusion of inhibitor was found by conducting dose–response studies with specific growth rate as the main response variable. No negative effects on feed conversion ratio or nitrogen digestibility were observed at this level. In protein sources studies the addition of potato protease inhibitor to a fishmeal based diet increased specific growth rate by 14%. When a proportion of the fishmeal was replaced with hydrolysed protein (fish silage) the addition of the inhibitor resulted in a 31% increase in specific growth rate. Absorption of amino acids from the gastrointestinal tract into the blood was investigated in two experiments using ¹⁴C-labelled algal ( Synechoccus leopoliensis ) protein. The absorption pattern of ¹⁴C-labelled amino acids was altered by adding potato protease inhibitor when the algal protein was supplied in intact form, but not when the algal protein was hydrolysed. The absorption of amino acids from a hydrolysed protein was significantly faster than from intact protein. The enzymatic activity of pepsin in the stomach and of trypsin, chymotrypsin, carboxypeptidases A and B in the different segments of the intestine changed significantly with increasing inclusion of potato protease inhibitors in the diet.     

Evaluation of flash dried yeast as a nutritional supplement in plant‐based practical diets for Pacific white shrimp Litopenaeus vannamei

Growth and digestibility trials were conducted to evaluate the use of flash dried yeast (FDY) as a supplement in practical shrimp feeds. The six‐week growth trial evaluated the effects of FDY supplementation (0, 10, 20, 40 and 60 g kg^–1) in the plant‐based practical diet on the performances and proximate compositions of juvenile Pacific white shrimp, Litopenaeus vannamei. Final biomass, final mean weight, per cent weight gain (WG), feed conversion (FCR) and protein retention efficiency (PRE) of Pacific white shrimp were not significantly influenced when FDY was added up to 40 g kg^–1 of the diet. However, 60 g kg^–1 FDY supplementation significantly reduced growth, feed utilization and protein retention. Supplementation of FDY in the practical diets of Pacific white shrimp did not affect protein, moisture, lipid, crude fibre, and ash content of whole shrimp body. Apparent digestibility coefficients of energy, protein, and amino acid (AA) for FDY were determined using chromic oxide as an inert marker and the 70:30 replacement technique. The energy and protein digestibility of FDY were 38.20% and 53.47%, respectively, which were significantly lower than fishmeal (FM) and soybean meal (SBM) that were run at the same time. Most amino acid digestibility of FDY was lowest among the three ingredients tested. Results of this work indicated that energy, protein and amino acid digestibility of FDY are lower compared to SBM and FM, and high levels supplementation (≥60 g kg^–1) of FDY can cause negative effects to the growth response of Pacific white shrimp. Based on these results, further research regarding the effects of the low level inclusion of FDY in practical diets on immune responses of Pacific white shrimp is warranted.     

Growth performance of juvenile pacu (Piaractus mesopotamicus) and dourado (Salminus brasiliensis) fed with lyophilized bovine colostrum

Growth performance was evaluated in juvenile pacu (Piaractus mesopotamicus) and dourado (Salminus brasiliensis) fed diets containing 0%, 10% and 20% of lyophilized bovine colostrum for 60 days. The performance variables of weight gain, relative weight gain, feed intake, feed conversion ratio, specific growth rate, total protein intake and protein efficiency ratio were evaluated as well as apparent digestibility coefficients of protein and energy in the diets. Inclusion of bovine colostrum did not induce differences in the performance of pacu and dourado (P > 0.05), indicating that the diets were adequate and met the nutritional needs of the juveniles. The protein digestibility in both species was improved with the inclusion of the bovine lacteal secretion. Based on the variables studied, the diets with lyophilized bovine colostrum inclusion were nutritionally suitable for both pacu and dourado indicating the possibility to use this lacteal secretion as a partial substitute of dietary protein.     

Partial replacement of fish meal by porcine meat meal in practical diets for Pacific white shrimp (Litopenaeus vannamei)

In this study, it evaluated the growth performance of the Pacific white shrimp Litopenaeus vannamei in response to the replacement of fish meal with rendered porcine meat meal (PMM) in its diet. Six isolipidic and isonitrogenous diets were formulated with 0, 25, 35, 45, 55 or 65% replacement of fish meal with PMM on a protein basis. Shrimp grew from 0.55 g to > 3.6 g during the 41-day experimental period. Specific growth rate (SGR) was significantly lower when PMM inclusion was 26.18% or greater, replacing more than 45% fish meal protein. A significant negative relationship was observed between growth response and the level of fish meal protein replacement with PMM protein. Methionine content decreased as PMM inclusion levels increased, consequently compromising growth performance. Dry feed intake (DFI) and the feed conversion ratio (FCR) were unaffected by fish meal replacement levels. The protein efficiency ratio (PER) was highest at the lowest PMM inclusion level. Apparent protein digestibility coefficient (APDC) for PPM was 66.2%. Experimental diets D-0 and D-25 had apparent dry matter digestibility (ADMDs) ranging from 77–81% and ADPs from 82–85%, while the diets with higher PMM inclusion (D-35 to D-65) had a significantly lower ADMD range (70–72%) and APD range (73–78%). It is concluded that porcine meat meal is an acceptable alternative animal protein source that can replace up to 35% of fish meal protein in shrimp diets without significant adverse effects on growth, survival, FCR, PER and body composition.     

不同蛋白水平下添加晶体氨基酸对罗非鱼生长和饲料利用的影响

实验主要研究不同蛋白水平下添加晶体氨基酸(CAA)对罗非鱼生长和饲料利用的影响。实验饲料为全植物蛋白实用饲料,通过调整豆粕含量,设置出4个蛋白梯度(蛋白含量:34%、32%、30%和28%),每个蛋白水平下设置不添加CAA组(34CP-28CP)和添加CAA组(34AA-28AA),后者通过添加赖氨酸、蛋氨酸和苏氨酸,使之在饲料中的水平分别达到1.43%、0.75%和1.05%,满足罗非鱼的必需氨基酸需要量。实验结果显示,34AA、30AA和28AA组的增重率和特定生长率(1074.75%、951.60%、815.12%和4.11%、3.92%、3.69%)显著高于相应的不添加组(869.85%、641.25%、523.75%和3.79%、3.33%、3.05%),32AA与32CP之间则没有显著差异(917.45%对882.27%、3.87%对3.81%)。从增重率的增长幅度来看,30%和28%蛋白水平下添加CAA的效果更为明显(48.4%、55.6%对23.6%、4%)。饲料效率、蛋白质效率、蛋白质保留率和能量保留率方面,34CP、34AA、32CP和32AA4组间没有显著差异;30CP和28CP组显著低...     

Replacement of fishmeal with rice protein concentrate in practical diets for European sea bass Dicentrarchus labrax reared at winter temperatures

As no information is available regarding the efficacy of using rice protein concentrate (RPC) to replace fishmeal (FM) in diets for European sea bass (Dicentrarchus labrax), a trial was conducted to determine the optimum inclusion for European sea bass juveniles. Diets were formulated to replace 25%, 50% and 75% of fishmeal with RPC. Additional high level inclusion diets (50% and 75%) were supplemented with lysine and methionine to determine if these were limiting factors. Fish (18.0 ± 0.06 g) were fed the experimental diets for 12 weeks. The final mean weight and specific growth rate (SGR) were significantly higher in fish fed the control diet (diet FM) and low level RPC (diet RPC25) than in fish fed the other diets. The supplementation of the amino acids had a positive effect on growth, elevating the final weight of the high level RPC (RPC75 + AA) group above that of the non‐supplemented group (RPC75). However, this was still not comparable to fish fed FM and RPC25 diets. No significant differences in body composition were observed. A digestibility study demonstrated an inverse relationship between elevating inclusion levels of RPC and apparent digestibility coefficients (ADCs) for dry matter and lipid, with significantly lower values than the control being observed with RPC inclusions above 25%. The mesenteric fat index followed this trend. Circulating leucocyte levels, leucocyte ratios and serum lysozyme activity remained unaffected by dietary treatment. However, compared with the control group, fish fed RPC75, RPC50 + AA RPC75 + AA displayed significantly lower haematocrit values. The present study demonstrates that the inclusion of RPC at 140 g kg^?1 (effectively replacing 25% of FM content) does not compromise European sea bass growth performance, body quality or basic haematological parameters. It is suggested that future studies including higher levels test the efficacy of additional amino acid supplementation (e.g. tryptophan).     

Evaluation of a novel bacterial biomass as a substitution for soybean meal in plant‐based practical diets for Pacific white shrimp Litopenaeus vannamei

Three growth trials and a digestibility trial were designed to evaluate the efficacy of a novel bacterial biomass (BB) in commercial‐type feed formulation for Pacific white shrimp, Litopenaeus vannamei. In trial 1, the basal diet was supplemented with 0, 60 and 120 g/kg BB to replace soybean meal (SBM). Significant improvement was observed in the survival when BB was incorporated in the diets. However, shrimp fed diets containing 120 g/kg BB exhibited significantly lower weight gain (WG) and higher feed conversion ratio (FCR). To confirm the results from trial 1 and explore the effects of BB supplementation at low levels, the basal diet was incorporated with 0, 10, 20, 40, 60 and 120 g/kg BB to replace SBM in trial 2. Significant reductions in WG, FCR, lipid content of whole body, protein retention efficiency and most amino acids retention efficiency were detected in shrimp fed with diet containing 120 g/kg BB. Trial 3 was designed to elucidate whether the digestible protein is the cause of reduced growth. No improvements in terms of growth performance and FCR were detected in the treatments balanced for digestible protein. Apparent digestibility coefficients of energy, protein and amino acid (AA) for BB were determined using chromic oxide as an inert marker and the 70:30 replacement technique. The energy, protein and individual amino acid digestibility coefficients of BB were significantly lower than those of fish meal (FM) and SBM that were given at the same time. Results of this study indicated that BB can be utilized up to 40 g/kg in shrimp feed without causing a decrease in growth. However, supplementations (≥60 g/kg) of BB can result in negative effects on growth response, FCR and protein as well as amino acids retention efficiency. At the lower levels of inclusion, shrimp performance was improved when BB was supplemented on a digestibility basis; however, at the higher level of inclusion, there was no improvement, indicating there may be other nutrients limiting. Based on enhanced survival in the treatment with BB supplementation in trial 1, further research regarding the immune effects of BB in practical shrimp feed will be necessary.     

Digestibility of plant protein-based diets by largemouth bass Micropterus salmoides

Commercial farming of carnivorous fish demands the reduction of environmental impact of feeds; that requires minimal use of dietary animal protein. This study investigated the digestibility of diets formulated exclusively out of plant protein, added feed attractants, by the carnivore largemouth bass, Micropterus salmoides . Juvenile largemouth bass (14.0 ± 1.0 cm) conditioned to accept artificial, dry feed were confined in polypropylene cages and fed ad libitum in three daily meals, seven experimental diets containing varying levels of vegetable and animal protein sources, added of different feed stimulants. After last daily meal, cages were transferred to cylindrical–conical-bottomed, 200-L aquaria, where faeces were collected by sedimentation into refrigerated containers, preserved and later analysed for chemical composition. Soybean meal can be used as partial substitute of animal protein in diets for largemouth bass; the poultry by-product meal shows as a good option as animal protein source in these rations. Control treatment – 50PP : 50AP – yielded best performances; the need for the use of fish meal in the formulation for carnivorous diets is, at least, questionable. Results of the digestibility trials demonstrated the importance of determining the diet digestibility, if precision in the formulation of least-cost feeds for carnivorous fish is the ultimate goal.     

Preliminary evaluation of pea seed meal in diets for gilthead sea bream (Sparus aurata) juveniles

Juvenile gilthead sea bream with a mean initial body weight of 5 g were fed for 12 weeks with experimental diets containing 10% and 20% fishmeal protein (sole protein source in the control diet) replaced by processed pea seed meals. The processed pea seed meals were dehulled, defibred, extruded and microground pea seed meal (PSM1) or whole pea treated by infrared radiation and ground (PSM2). Apparent digestibility coefficients of the experimental diets were determined in a separate trial. At the end of the growth trial there were no significant differences in growth performance, feed utilization or whole-body composition among experimental groups. There were no differences in apparent protein digestibility among experimental groups (except for fish fed PSM1 at the lowest inclusion level). Both dry matter and energy digestibility of the diets, including PSM2 and with the highest inclusion level of PSM1, were significantly lower than those of the control diet. The results of this study suggest that pea seed meal may replace up to 20% fishmeal protein in diets for gilthead sea bream juveniles without affecting fish performance. Further studies should focus on technological treatments to increase utilization of pea seed meal carbohydrate, as both apparent dry matter and energy digestibility were affected by dietary inclusion level and by pea seed meal processing method.     

The effect of dietary protein replacement by crystalline amino acid on growth and nitrogen utilization of turbot Scophthalmus maximus juveniles

A study was conducted to evaluate the effect of partial replacement of dietary fish meal by crystalline amino acids on growth performance, feed utilization, body composition and nitrogen utilization of turbot juveniles.

Four diets were formulated to be isolipidic (12% DM) and isonitrogenous (8% DM). A fish meal based diet was used as control. In the experimental diets, a crystalline amino acid (AA) mixture was used to partially replace fish meal, corresponding to a non-protein nitrogen content of 19, 37 and 56%, respectively (diets 19AA, 37AA and 56AA, respectively). The overall amino acid profile of the experimental diets resembled that of the whole-body protein of turbot. Each experimental diet was fed to triplicate groups of 20 fish (initial body weight of 31.8 g) twice daily to apparent satiation for 42 days. During the trial water temperature averaged 18 °C.

Final body weight, weight gain (g kg ABW^− 1 day^− 1) and specific growth rate were not different between the control and 19AA diet but significantly decreased with the increase of crystalline-AA inclusion from 19 to 56%. Feed intake and feed efficiency of fish fed the control and diet 19AA were similar and significantly higher than those of fish fed the 56AA diet. At the end of the growth trial, there were no significant differences in whole-body composition among groups. Hepatosomatic index was also unaffected by dietary treatments.

Nitrogen retention (g kg ABW^− 1 day^− 1) of fish fed the control and the 19AA diets were similar and significantly higher than that of fish fed the other diets. Expressed as a percentage of the nitrogen intake, N retention was significantly higher with the control than with the 37AA and 56AA diets.

Daily ammonia excretion (mg kg ABW^− 1 day^− 1) of fish fed the control diet was significantly higher than that of fish fed the 37AA and 56AA diets, while daily urea excretion (mg kg ABW^− 1 day^− 1) did not significantly differ among treatments. Non-fecal nitrogen (ammonia + urea) excretion (mg kg ABW^− 1 day^− 1) was significantly higher for fish fed the control diet than in those fed the 37AA and 56AA diets. However, as percent of N intake, ammonia excretion and non-fecal N excretion were significantly higher in fish fed the 56AA diet than in those fed the control and 19AA diets.

Specific activity of glutamate dehydrogenase, alanine and aspartate aminotransferases did not significantly differ among experimental groups.

In conclusion, in diets with an overall amino acid profile resembling that of the whole-body protein of turbot, crystalline-AA may replace 19% of dietary protein without negatively affecting growth performances or feed utilization efficiency. However, higher protein replacement levels of protein-bound-AA by crystalline-AA severely depressed growth performance.     

Apparent digestibility coefficients of several protein sources,and replacement of fishmeal by porcine meal in diets of Japanese seabass,Lateolabrax japonicus,are affected by dietary protein levels

A digestibility and a growth trial were conducted in this study respectively. Firstly, the apparent digestibility coefficients (ADC) of nutrients and energy in meat and bone meal, porcine meal (PM), hydrolysed feather meal, poultry by‐products meal, fishmeal (FM), soybean meal and spray‐dried blood meal were determined. In experiment 2, an 8‐week growth trial was conducted to evaluate the effects of the substitution of FM by PM under the digestible ideal protein concept at two protein levels in the diets of Japanese seabass, Lateolabrax japonicus. A FM‐based control diet (FM diet; FM: 320 g kg^?1, crude protein: 434.9 g kg^?1, crude lipid: 124.6 g kg^?1) and three other diets were formulated to contain 115 g kg^?1 PM and only 160 g kg^?1 FM. Two diets were formulated on a crude protein basis without (PM diet) or with (PMA diet) essential amino acid (EAA) supplementation respectively. A low‐protein diet was designed (LPMA diet, crude protein: 400.9 g kg^?1, crude lipid: 96.3 g kg^?1) with the same level of FM and PM but with the same digestible protein/ digestible energy and EAA profile as the FM diet. The results showed that nitrogen and total amino acid digestibility of the tested ingredients were ranged from 85.6% to 95.5% and from 87.6% to 95.5% respectively. Apparent digestibility coefficients of protein for FM and PM were 91.2% and 95.9% respectively. In the growth trial, the weight gain rate and feed conversion ratio of fish fed the PMA diet did not show a significant difference from those of the control group, but were significantly higher than those of the PM and LPMA groups (P<0.05). Growth was related linearly to lysine and methionine intakes. It was shown that PM could be utilized in the Japanese seabass diet up to 115 g kg^?1 to replace about 160 g kg^?1 of FM protein under an ideal protein profile. Essential amino acid deficiency (diet PM) or a lower protein level despite having an ideal amino acid profile (diet LPMA) could not support the optimal growth of Japanese seabass.     

Free amino acid distribution in plasma and liver of juvenile cobia (Rachycentron canadum) fed increased levels of lizardfish silage

Juvenile cobia (Rachycentron canadum) (100 g) were fed four moist diets (447–476 g kg^?1 dry wt) where 0, 130, 260 or 390 g kg^?1 of concentrated lizardfish (Saurida undosquamis) silage replaced fresh lizardfish, respectively. Blood and livers were sampled at 0, 6, 12, 24 and 48 h postfeeding at the end of the 3‐week experiment. At 6 h postfeeding in all groups, maximum concentrations of most plasma essential amino acids were observed, while significantly lower levels of most non‐essential amino acid levels were recorded compared to the other sampled times. At 6 and 12 h after feeding, the concentration of most plasma free amino acid (FAA) increased with an increase in dietary fish silage levels. Most FAA in livers of all groups peaked at 12 and 24 h postfeeding. However, at 48 h postfeeding, concentrations of most plasma FAA were significantly higher in fish fed 0% silage‐based diet than in fish fed the other diets (4999 versus 3390–4339 nmol AA mL^?1 plasma). Growth rates and feed utilization were significantly lower in cobia fed 26% or 39% silage‐based diets than in fish fed 0% or 13% silage‐based diets. Different levels of silage protein thus seemed to have effects on growth and feed utilization efficiency of juvenile cobia. Results from this study support the premise that fish silage can be included until 130 g kg^?1 in cobia diets.     

Effect of predigested protein on growth and survival of Atlantic halibut larvae (Hippoglossus hippoglossus L.)

In this study Atlantic halibut (Hippoglossus hippoglossus L.) larvae (0.12 ± 0.04 g) were, from day 40 post first feeding, offered six diets in which 10% or 30% of the dietary protein was hydrolysed with (a) pepsin (P), (b) pepsin + trypsin (PT) or (c) pepsin + trypsin + chymotrypsin (PTC). In addition, a diet without hydrolysed protein was offered, and enriched Artemia was fed as control. The amount of soluble protein increased progressively with the enzyme treatments P, PT and PTC and with higher inclusion levels of hydrolysed protein. Survival was highest among the larvae offered Artemia (83 ± 0%) or the diet 10P (10% pepsin hydrolysed protein; 67 ± 4%). The diet 10P supported survival significantly better than the more hydrolysed diets 10PTC, 30P, 30PT and 30PTC, but not significantly better than the non‐hydrolysed diet and 10PT. Specific growth rate (SGR) was 1.76 ± 0.20 in average for all groups of larvae and was not significantly affected by the diets. Still, the larvae offered pepsin hydrolysed diets tended to have better growth (2.10 ± 0.05 SGR; P < 0.06) than the larvae offered the other hydrolysed diets. The larvae offered the formulated diets did not differ in chemical composition.