Predicting dietary essential amino acid requirements for hybrid striped bass

Three experiments were conducted that were designed to evaluate our ability to predict essential amino acid (EAA) needs of hybrid striped bass using the quantified lysine requirement and whole‐body amino acid concentrations. In the first experiment, six diets containing various amino acid profiles were fed to triplicate groups of fish initially weighing 7.7 g per fish. At the end of the 8‐week experiment, no significant differences were detected in growth rates or feed efficiencies (FE) between fish fed a practical diet containing 510 g kg^?1 herring fish meal (FM) and fish fed a purified diet containing the amino acid profile of herring fish meal (CAA‐FM). Growth responses of fish fed purified diets containing 100 (HSB), 110 (HSB110), 120 (HSB120) or 140 g 100 g^?1 (HSB140) of the amino acid profile of hybrid striped bass whole‐bodies were significantly lower than those of fish fed diet FM. In the second experiment, triplicate groups of fish (5.6 g per fish) were fed diets containing various energy : protein (E : P) ratios (34.8, 41.2, 47.5 and 53.9 kJ g^?1 protein) and one of two amino acid profiles (CAA‐FM and HSB120) in a 4 × 2 factorial design. Carbohydrate concentration was varied to achieve the desired energy concentrations. At the end of the 8‐week experiment, weight gain and FE were significantly higher in fish fed diets formulated to simulate the amino acid profile of herring fish meal (CAA‐FM) compared with fish fed diets formulated to contain 120 g 100 g^?1 of the amino acid profile of hybrid striped bass whole‐bodies (HSB120). Weight gain, FE and survival data indicated the optimum dietary E : P was 41.2 kJ g^?1 protein. Dietary treatments in the final experiment included three amino acid profiles and four levels of lipid in a 3 × 4 incomplete factorial design. Dietary amino acid treatments included the amino acid profile of herring fish meal (CAA‐FM) or 120 g 100 g^?1 of the predicted EAA requirement profile for hybrid striped bass (HSB120). The amino acid profile of the remaining dietary treatment (PRED+) was similar to that of the HSB120 treatment, but contained additional threonine, isoleucine and tryptophan. Diets CAA‐FM and HSB120 contained either 90, 130, 170 or 210 g kg^?1 lipid, whereas diet PRED+ contained 130 g kg^?1 lipid. Dietary treatments were fed for 10 weeks to triplicate groups of fish initially weighing 81.0 g per fish. Weight gain and FE were not significantly affected by dietary amino acid profile. Feed efficiency was significantly reduced in fish fed diets containing 210 g kg^?1 lipid compared with fish fed diets containing 90–170 g kg^?1 lipid. Intraperitoneal fat (IPF) ratio and hepatosomatic index (HSI) values generally increased as dietary lipid concentrations increased. Total liver lipid concentrations were significantly reduced in fish fed diets containing 210 g kg^?1 lipid compared with those of fish fed 90–130 g kg^?1 lipid. Results of this study indicate an appropriate dietary amino acid profile can be predicted for hybrid striped bass using the quantified lysine requirement and whole‐body amino acid concentrations. Further, the optimum E : P appears to be 40 kJ g^?1 protein.     

Establishing the optimum dietary essential amino acid pattern for silvery‐black porgy (Sparidentex hasta) juveniles by deletion method

A 6‐week feeding trial was conducted to estimate the optimum dietary essential amino acid (EAA) pattern for silvery‐black porgy juvenile based on the AA deletion method. Eleven isonitrogenous and isoenergetic diets were formulated containing 60% of fish meal nitrogen and 40% of crystalline AA nitrogen. In the control diet, the EAA profile was made similar to fish meal protein. Ten other diets were formulated similar to the control diet but replacing 40% of each EAA by a mixture of non‐essential amino acids. Triplicate groups of fish (initial body weight of 4.7 g) were handfed with the experimental diets, three times a day, to visual satiation, for 42 days. At the end of the trial, final body weight of all EAA‐deficient groups was lower than that of control group, ranging from 6.3% of reduction with arginine‐deficient diet to 39.4% of reduction with lysine‐deficient diet, relatively to the control group. Based on the relationship between nitrogen retention and EAA intake of the control and EAA‐deficient diets, the optimal dietary EAA profile for silvery‐black porgy juveniles was estimated to be (g 16/g N): arginine 5.3, lysine 6.0, threonine 5.2, histidine 2.5, isoleucine 4.6, leucine 5.4, methionine + cysteine 4.0 (in a diet containing 0.6 cysteine), phenylalanine + tyrosine 5.6 (in a diet containing 1.9 tyrosine), tryptophan 1.0 and valine 4.6.     

Whole-body amino acid pattern of juvenile,preadult, and adult pacu,Piaractus mesopotamicus,with an estimation of its dietary essential amino acid requirements

In the present study, juvenile (live body weight, 54.3 ± 8.2 g), preadult (live body weight, 822.5 ± 33.9 g), and adult (live body weight, 1,562.8 ± 41.8 g) pacu, Piaractus mesopotamicus, were used to estimate their dietary essential amino acid (EAA) requirements using the whole-body amino acid (AA) pattern. The results showed that whole-body moisture, crude protein, total lipid, and ash contents expressed on a wet weight basis (%) were significantly different among the studied growth phases. No significant differences were observed in the dietary EAA requirements estimated for the three growth phases of pacu. These dietary EAA requirements were found to be different than those previously estimated for the same fish through its muscle AA pattern. Based on whole-body EAA to total EAA ratios {A/E ratios; [(each EAA/total EAA) × 1,000]}, EAA requirements were estimated to be histidine (0.42%), arginine (1.36%), threonine (0.82%), valine (0.90%), methionine (0.45%), isoleucine (0.83%), leucine (1.29%), phenylalanine (0.74%), lysine (1.64%), and tryptophan (0.14%) for pacu. These estimated requirements may serve as a reference line in the formulation of practical and experimental diets until dose–response-based optimum EAA requirements are available for pacu.     

Effects of dietary essential amino acid deficiencies on the growth performance and humoral immune response in silvery‐black porgy (Sparidentex hasta) juveniles

A 6‐week feeding trial was conducted for determining the effects of dietary essential amino acids (EAA) deficiencies on growth performance and non‐specific immune responses in silvery‐black porgy juveniles (4.7 ± 0.1 g initial weight). Eleven isoproteic (ca. 47%) diets were formulated including a control diet containing the optimum quantity of EAA, and ten EAA‐deficient diets. All diets contained 36% fish meal and 18.5% crystalline EAA and non‐essential amino acids (NEAA) as the main source of dietary proteins. All the EAA and NEAA incorporated in the crystalline amino acids mixture of the control diet simulated the amino acids profile of the fish meal. The other 10 EAA‐deficient diets were formulated by the deletion of each of the 10 EAA (crystalline form) from the control diet and replaced by a mixture of NEAA for the adjustment of dietary nitrogen contents. At the end of the experiment, fish fed with threonine‐deficient diet showed the lowest survival rate (p < .05), whereas growth performance decreased in fish fed all EAA‐deficient diets, although the reduction in body growth varied depending on the EAA considered. Plasma total protein decreased in all experimental groups except for fish fed the phenylalanine‐deficient diet. Fish fed with arginine‐ and lysine‐deficient diets had the lowest plasma C3, C4, lysozyme, total immunoglobulin and total superoxide dismutase activity (p < .05). Present results indicated that lysine, methionine and threonine were the most limiting EAA in terms of growth performance; however, arginine, threonine and lysine were the most limiting EAA for innate immunity responses in silvery‐black porgy juveniles.     

Assessment of the ideal ratios of digestible essential amino acids for pacu,Piaractus mesopotamicus,juveniles by the amino acid deletion method

The present study aimed to determine the ideal ratios of digestible essential amino acids (EAAs) for pacu (Piaractus mesopotamicus) juveniles by the amino acid (AA) deletion method. A completely randomized design which consisted of 11 treatments and three replicates each was used. The treatments included a control diet (CD) containing 55% of nonpurified natural ingredients and 45% of purified synthetic amino acids and ingredients, and other ten isonitrogenous and isoenergetic EAA limiting diets (LDs), each being deficient in 44.4 ± 0.02% of the respective EAA. Pacu juveniles with initial average body weight of 6.22 ± 0.09 g were distributed among 33 fiber glass tanks. Fish were fed with semipurified and extruded diets for 113 days two times a day until apparent satiation. The ideal ratio of each dietary EAA was calculated on the basis of the relationship between body N retention and amount of EAA deleted from the respective EAA LD. Based on the AA deletion method, the ideal ratios of digestible EAAs for pacu juveniles, relative to lysine requirement of 100% were estimated as: methionine 14.6%, threonine 35.0%, tryptophan 6.6%, arginine 62.8%, histidine 13.6%, isoleucine 26.3%, leucine 43.7%, phenylalanine 27.2%, and valine 35.8%.     

Assessment of requirement values for essential amino acids in the prawn, Marsupenaeus japonicus (Bate)

The requirements of juvenile prawn, Marsupenaeus japonicus (Bate), 0.79 g initial body weight, for essential amino acids (EAA) were evaluated based on the daily increase of each EAA in the whole body when the prawn was maintained on a diet with a high nutritive value (a casein‐squid protein‐based diet). The quantities of each EAA needed daily for growth and maintenance of prawn are conceived to correspond to the daily requirements of this prawn species for EAA. Therefore, these requirement values of respective EAA should be supplied from dietary proteins. To determine these values, protein and amino acids of the whole body of the prawn were quantified before and after feeding experiments, and the quantities of respective EAA needed to meet the requirements were estimated based on the EAA profile of the whole body protein of prawn. As a result, the contents of EAA in dietary proteins (%) needed to meet the requirements of the prawn for EAA were assessed to be: threonine (2.3), methionine (1.3), valine (2.4), isoleucine (2.3), leucine (3.4), phenylalanine (2.6), lysine (3.2), histidine (1.1), arginine (2.9) and tryptophan (0.6), respectively, when the prawn are fed 50% protein diet with 90% protein digestibility at a ration size of 2% (% of body weight).     

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.     

Total sulphur amino acid requirement and cystine replacement value for fingerling rohu,Labeo rohita: effects on growth,nutrient retention and body composition

Two feeding experiments were conducted to quantify the total sulphur amino acid (TSAA) requirement and replacement value of cystine for methionine for fingerling Labeo rohita. In Experiment I, isonitrogenous (380 g kg^?1 CP) and isocaloric (17.90 kJ g^?1 GE) amino acid test diets with graded levels of methionine (4, 6, 8, 10, 12, 14 g kg^?1 dry diet) and 0.4 g kg^?1 cystine were fed to fish (4.62 ± 0.2 cm; 0.66 ± 0.1 g) and methionine requirement determined by analysing absolute weight gain (AWG) (5.48), feed conversion ratio (FCR) (1.26), protein retention efficiency (PRE%) (39%) and energy retention efficiency (ERE%) (85%) data which were best at 10 g kg^?1 methionine of dry diet. In Experiment II, six diets with different ratios of L‐cystine and L‐methionine on equimolar sulphur basis were fed to fish (4.71 ± 0.1 cm; 0.69 ± 0.2 g) under identical conditions. Maximum AWG (5.58), best FCR (1.24), PRE (41%) and ERE (86%) in fish fed Diet IV indicated cystine replacement value to be 40%. On the basis of the broken‐line and second‐degree polynomial regression analyses of results obtained in Experiments I and II, it is concluded that inclusion of TSAA in the range of 25.2–31.31 g kg^?1 of protein is optimum of which 33–39% could be spared by cystine.     

Influence of multiple amino acid supplementation on the performance of rainbow trout, Oncorhynchus mykiss (Walbaum), fed soya based diets

Using rainbow trout, Oncorhynchus mykiss (Walbaum), of approximately 50 g, a 63 day feeding trial was undertaken to evaluate the efficacy of individual and multiple amino acid supplements in diets where soyabean meal was used as the principle protein source. Iso-nitrogenous diets (45% crude protein) were formulated where the control diet (F) contained fishmeal as the reference protein and a solvent extracted soyabean meal (S) replaced approximately 66% of this protein source. The soyabean containing diets were then supplemented with crystalline amino acids thus; methionine only, dual supplemented with two methionine and lysine levels and finally, a supplement comprising methionine, lysine, tryptophan, threonine, arginine and histidine. The results showed that soyabean meal (SBM) was inferior to the reference protein when SBM was used to replace 66% of the fishmeal and that no significant restoration in growth, feed efficiency and apparent net protein utilization was obtained by either methionine only or dual methionine and lysine supplementation. However, by comparison with the fish fed the unsupplemented, single and dual supplemented diets, multiple amino acid incorporation was associated with significantly improved percentage weight gain, specific growth rate and marginal improvements in apparent net protein utilization. However, performance was not equal to that of the fish fed the fishmeal based control diet. The results are discussed with respect to the level of each of the essential amino acids (EAA) as a proportion of the total EAAs (A/E index) of test diets by reference to the whole body tissue amino acid profile of rainbow trout.     

Total sulphur amino acid requirement and maximum cysteine replacement value for methionine for fingerling Catla catla (Hamilton)

Two separate 12 weeks feeding trials were performed to quantify the total sulphur amino acid (TSAA) requirement (experiment I) and cysteine replacement value for methionine (experiment II) of fingerling Catla catla. In experiment I, six casein–gelatin based (33% crude protein; 16.72 kJ g^?1 gross energy) diets with graded levels of TSAA (0.56%, 0.81%, 1.06%, 1.31%, 1.56%, 1.81% dry diet) were fed to triplicate groups of fish (3.55 ± 0.06 cm; 0.65 ± 0.02 g) near to satiation. The TSAA requirement was determined by quadratic regression analysis of absolute weight gain (AWG), protein efficiency ratio (PER), feed efficiency (FE), protein gain (PG) and TSAA gain (TSAAG) against dietary TSAA concentrations at 95% maximum response. Above analysis revealed that inclusion of TSAA at 1.28% dry diet (1.22% methionine + 0.06% cysteine), corresponding to 3.87% of dietary protein is optimum. In experiment II, to determine the replacement value of cysteine for methionine, six diets containing 1.28% TSAA determined in experiment I with different ratios of l ‐methionine and l ‐cysteine (80:20, 70:30, 60:40, 50:50, 40:60, 30:70) on equimolar sulphur basis were fed to fish (3.65 ± 0.08 cm; 0.67 ± 0.04 g). Broken‐line regression analysis of AWG, PER, FE, PG and TSAAG against varying methionine to cysteine ratios yielded the optimum cysteine replacement value at 40.3%. Based on above analysis, it is recommended that inclusion of 1.28% dietary TSAA, corresponding to 3.87% of dietary protein is optimum of which 40.3% could be spared by cysteine. Data generated during this study would be useful in formulating TSAA balanced, cost‐effective feeds for the intensive culture of this fish.     

Methionine Requirement in Practical Diets of Juvenile Nile Tilapia,Oreochromis niloticus

Two feeding experiments were conducted to confirm methionine requirement in practical diets of juvenile Nile tilapia, Oreochromis niloticus. Test diets used in both experiments contained 414 kcal gross energy, 28 g protein, and 5 g lipid per 100 g diet. In the first experiment, seven diets were made using cottonseed meal (CSM), dehulled solvent‐extracted soybean meal (DSESM), and gelatin as intact protein sources. Methionine was added to five of these diets at 0.03 or 0.06% increments to produce methionine levels ranging from 0.33 to 0.57% of the diet. Each diet was fed to four replicate groups of male juvenile Nile tilapia (5.62 ± 0.13 g) in a recirculation system for 8 wk. Broken‐line regression analysis of weight gain indicated that methionine requirement of juvenile Nile tilapia was 0.49% of the diet or 1.75% of dietary protein at cystine level of 0.45% of the diet. The second experiment was designed based on methionine requirement determined in the first experiment and also contained seven test diets. The first six diets contained CSM and DSESM as protein sources. Methionine was added to five of these diets at an increasing rate of 0.06% to produce methionine levels ranging from 0.49 to 0.79% of the diet. In the last diet (Diet 7), a portion of DSESM was replaced by gelatin to reduce methionine level to 0.33% of the diet in order to test whether methionine is limited. Each diet was also fed to four replicate groups of male juvenile Nile tilapia (2.32 ± 0.06 g) in a recirculation system for 9 wk. At the termination of the second experiment, there were no significant differences in terms of weight gain, survival, and feed efficiency ratio (FER) among the fish fed the first six diets. However, weight gain and FER of the fish fed these diets were significantly better than those fed Diet 7, confirming the methionine requirement value as has been determined in the first experiment.     

The optimum dietary essential: nonessential amino acid ratio for rainbow trout (Oncorhynchus mykiss), which maximizes nitrogen retention and minimizes nitrogen excretion

Although the ratio of essential to nonessential amino acids (EAA:NEAA ratio) in dietary protein has important effects on protein utilization by fish, there has thus far been little research aimed at quantifying these effects. In this study, we investigated the effect of dietary EAA:NEAA ratio on nitrogen (N) utilization and excretion of rainbow trout (Oncorhynchus mykiss). A 6-week dose-response experiment was conducted, with 6 levels of dietary EAA:NEAA ratio, ranging from 23:77 to 66:34. Protein content of all diets was 350 g kg^?1. Each experimental diet was fed to four replicate tanks of fish (35 fish per tank). Fish were fed a limited ration on the first two feedings of each day, and were fed to apparent satiation on the third feeding of each day. Response variables included feed intake, weight gain, lipid deposition, thermal-unit growth coefficient (TGC), feed efficiency ratio (FER), N retention, and N excretion (g kg^?1 gain). Mean feed intake, weight gain, TGC, FER and N retention all increased as EAA:NEAA ratio increased up to 57:43, and then decreased slightly as EAA:NEAA ratio increased further to 66:34. Maximum mean N retention of 46% and minimum mean N excretion of 29 g N kg^?1 gain was achieved by fish fed the diet containing an EAA:NEAA ratio of 57:43. Non-linear regression using a 2^nd order polynomial equation showed that 95% of the maximum N retention could be achieved with an EAA:NEAA ratio of 46:54, and 98% with an EAA:NEAA ratio ranging from 49:51 to 62:38.     

Estimating the quantitative essential amino acid requirements of striped bass Morone saxatilis, using fillet A/E ratios

In order to determine the essential amino acid requirements (EAA) of striped bass Morone saxatilis , fillets were analysed to ascertain the relative amino acid concentrations for determining A/E ratios ((EAA/total EAA) × 1000)). Analysis of the striped bass fillets yielded the following concentrations of essential amino acids (g kg^–1) and A/E ratios, respectively: arginine, 12.5, 115; histidine, 5.1, 47; isoleucine, 8.0, 74; leucine, 17.1, 157; lysine, 20.2, 186; methionine + cysteine, 9.2, 85; phenylalanine + tyrosine, 16.0, 147; threonine, 9.8, 90; tryptophan, 1.9, 18; and valine, 9.1, 84. In two experiments, diets with graded levels of EAA were fed to striped bass weighing 111 ± 3 g and 790 ± 122 g per fish, respectively. In both experiments, the dietary A/E ratios were maintained in the same relative concentrations as determined in the striped bass fillets. Statistical analysis of weight gains, feed conversions and nitrogen balance indicated significant differences ( P  < 0.05) between treatments. Non-linear regression analysis of the response criteria pooled from both experiments yielded the following estimates of dietary EAA requirements (g kg^–1 dry diet) when digestible energy equalled 13.39 MJ kg^–1 diet: arginine, 14; histidine, 6; isoleucine, 9; leucine, 19; lysine, 22; methionine + cysteine, 10; phenylalanine + tyrosine, 17; threonine, 11; tryptophan, 3; and valine, 10. The use of fillet A/E ratios allows for the rapid estimation of quantitative EAA requirements and the development of species specific diets for new aquaculture species. The data presented here are the first to simultaneously describe all the dietary EAA requirements for M. saxatilis.     

Juvenile Atlantic salmon decrease white trunk muscle IGF‐1 expression and reduce muscle and plasma free sulphur amino acids when methionine availability is low while liver sulphur metabolites mostly is unaffected by treatment

We previously reported that juvenile Atlantic salmon with mean initial BW 11.5 g offed a methionine deficient diet had lower weight gain due to a reduced protein accretion, while lipid gain was unaffected. Muscle of the fish fed the methionine deficient diet was depleted for sulphur amino acids, while in liver, the concentration of these metabolites was maintained within narrow limits. We speculated whether this could be due to an increased muscle proteolysis to support a prioritized liver metabolism in fish fed the low methionine diets. In this study, we assessed whether genes associated with muscle proteolysis increased under methionine deficiency. The composition of the diets was similar to those used previously containing 1.6 or 2.1 g Met/16 g N. We confirmed that the fish fed the low methionine diet gained less protein compared to fish fed the DL‐methionine enriched diet (P = 0.014), but growth did not reduce significantly. Also the deficient fish maintained the concentrations of liver sulphur amino acids and reduced muscle free methionine. Several of the other free amino acids within muscle increased. Further, methylation capacity was maintained in liver but reduced in the muscle (P = 0.78 and 0.04, respectively). Gene expression of muscle IGF‐1 was lower (P = 0.008) and myosin light chain 2 tended (MLC2, P = 0.06) to be reduced in fish fed low methionine diet, concurrently the activity of cathepsins B+L increased (P = 0.047) in muscle of fish fed the low methionine diet. Gene expression of the muscle‐specific E3 ubiquitine ligases (Murf and MaFbx) was not affected by treatment. Thus, the lower protein gain observed in fish fed the low methionine diet may be caused by reduced protein synthesis in line with the reduced IGF‐1 gene expression in the white trunk muscle. Thus, to support metabolism, the dietary protein needs to be balanced in amino acids to support metabolism in all compartments of the body and secure maximal protein gain.     

Partial replacement of fishmeal with corn gluten meal,pea protein isolate and their mixture in diet of black sea bream (Acanthopagrus schlegelii) juveniles: Effects on growth performance,feed utilization and haematological parameters

Corn gluten meal (CGM), pea protein isolate (PPI) and their mixture (CPP, 1:1 ratio) were evaluated as fishmeal (FM) alternatives in black sea bream (Acanthopagrus schlegelii) juveniles (9.02 ± 0.12 g). A FM diet was designed as control, and other six diets had 20% and 40% FM protein replaced by CGM, PPI and CPP, respectively, with the supplementation of crystalline methionine, arginine and lysine. After the 8‐week feeding trial, significantly lower weight gain was found in fish fed the 40% CGM diet (p < .05), whereas other treatments had no statistical difference (p > .05). The values of feed efficiency ratio and feed intake, as well as proximate compositions of muscle and whole body, were not significantly influenced in all treatments. Apparent digestibility coefficients (ADCs) of dry matter, crude protein, threonine, valine, methionine, isoleucine, leucine, phenylalanine and lysine were significantly influenced by protein source. Fish fed the 40% CGM diet had significantly higher content of essential amino acid in muscle than that of the 20% PPI diet. Fish fed the 40% CGM diet had significantly lower content of serum cholesterol than other treatments (p < .05). Elevated serum superoxide dismutase activity was found in fish fed the 40% plant protein diets. In conclusion, between 20% and 40% FM protein could be replaced by CGM, while about 40% FM protein derived from PPI and CPP could be applied in black sea bream.     

Effects of varying dietary fatty acid profile on growth performance, fatty acid, body and tissue composition of juvenile pike perch (Sander lucioperca)

Pike perch (Sander lucioperca) has been identified as specie destined to diverse European inland aquaculture, but knowledge on the nutritional requirements is weak. Therefore, we investigated the effect of varying dietary fatty acid (FA) profile by partial replacement of fish oil (FO) with vegetable oils on growth, FA and body composition of juvenile pike perch. An extruded basal diet containing 59 g kg^?1 crude lipids (FO) was added with 60 g kg^?1 FO, 60 g kg^?1 linseed oil (LO) or 60 g kg^?1 soybean oil (SO). The resulting dietary FA composition differed mainly in the triglyceride fraction and was characterized by highest amounts of linolenic acid (18:3 n‐3) in the LO diet and linoleic acid in the SO diet. Diet enriched with FO contained highest contents of highly unsaturated FA 20:5 n‐3 (eicosapentaenic acid) and 22:6 n‐3 (docosahexaenic acid). Pike perch were held in a recirculation system and each feeding group (in triplicate) was fed with experimental diets at a daily rate of 35 g kg^?1 of biomass for 57 days by automatic feeders. Weight gain and specific growth rate of experimental feeding groups ranged between 18.47 and 19.58 g and 1.37–1.45% day^?1 and was not affected by the dietary composition indicating that FO can be replaced by vegetable oils without negative impact on growth performance. In contrast to the whole body and muscle composition, liver tissue was affected by the varying diets. Liver tissues of fish fed diets enriched with vegetable oils showed significantly increased lipid contents of 162 (LO) and 147 (SO) g kg^?1 and indicate decreased lipid utilization compared with fish fed FO diet (liver lipid content 112 g kg^?1). Nevertheless, hepatosomatic index of pike perch was not influenced by dietary lipid composition. The FA profile of pike perch was generally determined by the dietary FAs.     

Estimating maintenance amino acids requirements of fish through a nonlinear mixed modelling approach

Accurate estimates of maintenance requirement of amino acids are important for feed formulation. However, very little is known about maintenance requirements of essential amino acids in fish. A nonlinear mixed modelling approach was employed in this study to estimate maintenance requirements of essential amino acids of fish from published studies. The maintenance requirements of arginine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine were estimated to be 7.7 (±6.6), 9.8 (±2.4), 6.4 (±24.8), 9.1 (±13.7), 15.6 (±8.2), 18.4 (±1.9), 14.6 (±3.2), 5.4 (±4.4), 0.5 (±1.3) and 9.3 (±26.6) mg/kg BW^0.75/day respectively, whereas the maintenance requirements of these amino acids as a proportion of their total requirements for protein deposition were estimated to be 4.8%, 31.0%, 8.9%, 12.7%, 5.2%, 11.9%, 19.2%, 2.5%, 2.2%, 10.8% respectively. For most of the essential amino acids, the maintenance requirements represent a small proportion of total requirement (below 10%) with notable exceptions for histidine and phenylalanine. Results from this study suggest that maintenance requirements of fish cannot be assumed equal for all amino acids. The results can be used in developing factorial or mechanistic models of amino acid requirement and utilization.     

Partial or total replacement of fishmeal by solvent-extracted cottonseed meal in diets for juvenile rainbow trout (Oncorhynchus mykiss)

The effect of solvent‐extracted cottonseed meal (SCSM) as a partial or total replacement of fishmeal was studied in juvenile rainbow trout (Oncorhynchus mykiss). Six experimental diets SCSM0, SCSM25, SCSM50, SCSM75, SCSM75A and SCSMT, containing a gradient of SCSM 0, 152, 305, 465, 460 and 610 g kg^?1 to replace 0, 112.5, 225, 337.5, 337.5 and 450 g kg^?1 fishmeal protein were fed to triplicate groups (initial body weight of 39.2 ± 0.1 g) for 8 weeks. The diet SCSM75A was supplemented with lysine and methionine, to be similar to SCSM0 for juvenile rainbow trout. Faeces were colleted after 4 weeks of normal feeding for apparent digestibility coefficients (ADC) of dry matter, crude protein and gross energy determination. Total replacement of fishmeal adversely affected growth performance. Fish fed with diet SCSMT had significantly (P < 0.05) lower weight gain, specific growth ratio, feed conversion efficiency (FCE) and protein efficiency ratio than fish fed with other diets. The FCE of SCSM75 and SCSM75A were significantly lower (P < 0.05) than those of fish fed with SCSM0 diets. The ADC of the dry matter of SCSM75 and SCSMT were significantly lower than the SCSM0 diet, and the ADC of crude protein and the energy of SCSMT were the lowest (P < 0.05). The ADC of threonine, proline, alanine, valine, isoleucine, leucine, lysine and methionine of fish fed with diet SCSMT were lower. Lysine and methionine supplement positively affected the ADC of SCS75A diet. There were no significant differences in the fish body composition. It is shown that SCSM can be utilized in the juvenile rainbow trout diet up to 305 g kg^?1, to replace about 50% of fishmeal protein in this experiment.     

Total sulfur amino acid requirement of juvenile hybrid striped bass (Morone chrysops×M. saxatilis)

Two separate feeding trials were conducted to determine the total sulfur amino acid requirement of hybrid striped bass. Semipurified diets containing 35% crude protein from fish muscle and crystalline amino acids were supplemented with graded levels of methionine. Each diet was fed to juvenile fish in triplicate aquaria receiving freshwater for 8 weeks. Fish fed the basal diet which contained 0.38% methionine and 0.13% cystine experienced complete mortality within 1 week. Prior to death, some fish fed inadequate methionine were observed to have bilateral cataracts. Weight gain and feed efficiency of fish were significantly (P<0.01) affected by supplemental methionine. Regression analysis of weight gain data using the broken-line model indicated a total sulfur amino acid requirement (±s.e.) of 1.0% (±0.02%) of dry diet or 2.9% of dietary protein.     

Refined understanding of sulphur amino acid nutrition in hybrid striped bass, Morone chrysops♀×M. saxatilis♂

Previous studies have indicated that the level of total sulphur amino acids (TSAA) (methionine+cystine) is most limiting in practical diet formulations for hybrid striped bass (HSB), especially if animal feedstuffs are replaced with plant feedstuffs. Reduction in costly animal feedstuffs such as fish meal, while maintaining adequate dietary levels of TSAA, may enhance the cost effectiveness of production. Therefore, this study investigated three different aspects of sulphur amino acid nutrition of HSB including: (1) the efficacy of crystalline methionine hydroxy analogue (MHA) and liquid MHA (Alimet?) relative to l‐ methionine in meeting the requirement for TSAA; (2) the cystine‐sparing value for methionine; and (3) the influence of various sulphur amino acid supplements on ammonia excretion. During three separate feeding trials (2, 6 and 10 weeks in duration), juvenile HSB were fed various diets including a basal diet deficient in TSAA (0.33% or 0.51% of diet), and experimental diets supplemented on an equal‐sulphur basis with different levels of either l‐ methionine, Alimet? or crystalline MHA. Diets containing TSAA at 1% of diet and different ratios of cystine to methionine (60:40, 55:45, 50:50 and 45:55) were also fed to re‐evaluate the sparing effects of cystine on methionine. In trial 1, over the course of 10 weeks, Alimet? was 73% as effective in promoting weight gain as l ‐methionine at the same concentration while MHA was 83% as effective. After 6 weeks in trial 2, fish fed Alimet? at 1.25% of diet displayed similar growth performance as those fed TSAA at 1.0% of diet, while weight gain of fish fed Alimet? at 1% was only 58% of that displayed by fish fed TSAA at 1.0%. No significant differences in weight gain, feed utilization or survival were observed among fish fed diets containing various ratios of cystine to methionine, although the diet with 60:40 cystine to methionine had the lowest numerical responses. Inclusion of MHA or Alimet? did not affect TAN excretion of HSB. These findings will aid in refining diet formulations for HSB to ensure adequate sulphur amino acid nutrition.