Dietary Amino Acid Profile Research Articles

The optimum dietary essential amino acid profile for gilthead seabream ( Sparus aurata) juveniles

A study was undertaken to establish the optimum dietary essential amino acid (EAA) profile for gilthead seabream juveniles based on the amino acid (AA) deletion method. For that purpose 11 diets were formulated to be isonitrogenous (6.72% N) and isolipidic (18%). In the control diet half of the nitrogen was provided by protein bound-AAs (fish meal) and the other half by a mixture of crystalline L-AAs. The overall AA profile of this diet was made similar to that of fish meal protein. Ten other diets were formulated identical to the control except for the deletion of 45% of a single EAA in each diet and by adjusting the nitrogen level with a non-essential AA mixture. Each diet was assigned to four groups of 22 fish (initial body weight of 4.6 g) and the trial lasted 43 days at a water temperature of 25 °C. Fish were fed by hand, twice daily, using a pair-feeding scheme. At the end of the trial the relationship between nitrogen gain and AA intake of the test and control diets was determined. Based on these data, and assuming that nitrogen retention responds linearly to dietary EAA content when a given AA is limiting, the quantity of each EAA that can be removed from the control diet without affecting nitrogen retention was computed and the ideal dietary EAA profile for gilthead seabream juveniles was estimated. Expressed relative to lysine (= 100) A/E ratios were estimated to be: arginine, 108.3; threonine, 58.1; histidine, 36.8; isoleucine, 49.7; leucine, 92.7; methionine, 50.8; phenylalanine + tyrosine, 112.3; valine, 62.6; and tryptophan, 14.6. This EAA profile correlates tightly to the whole-body EAA composition of gilthead seabream ( R 2 = 0.99; p > 0.001).

Dietary effects on insulin and glucagon plasma levels in rainbow trout (Oncorhynchus mykiss) and gilthead sea bream (Sparus aurata)

The effects of dietary amino acid profile (based on muscle (M) or whole body composition (WB) and the balance between indispensable (IAA) and dispensable amino acids (DAA) in the diet, on plasma levels of insulin and glucagon, were analysed in rainbow trout and gilthead sea bream. Plasma insulin values (baseline and 6 h postfeeding) were higher in trout than in sea bream, but the relative postfeeding increase was more pronounced in sea bream. Within the same dietary amino acid profile, diets with lower IAA/DAA, had a lower effect on the postfeeding secretion of insulin in both species. Circulating levels of glucagon (baseline and postfeeding relative increases) were higher in sea bream. In trout, diets with WB amino acid profile had a greater secretory effect on postfeeding glucagon than did diets with M profile, while gilthead sea bream showed an inverse response to circulating glucagon with respect to diet. Muscle insulin and insulin growth factor-I binding parameters were not affected by the dietary regimen. The postfeeding glucagon response depends on both the dietary AA profile and the fish species, while that of insulin seems to be more uniform, and is affected in a similar way regardless of the species.

Influence of dietary amino acid profiles on growth performance and body composition of juvenile grouper Epinephelus coioides

Summary A feeding experiment was conducted to investigate the effects of dietary amino acid (AA) profiles on growth performance and body composition of juvenile grouper Epinephelus coioides (initial mean weight: 68.1 ± 1.0 g, mean ± SD). Five diets contained 30% fishmeal, 12% soy protein concentrate and 20% crystalline amino acids (CAAs); the control diet contained 54% fishmeal and 17% soy protein concentrate as intact protein sources. CAAs were added to the five diets to simulate the AA pattern found in white fishmeal protein (WFP), brown fishmeal protein (BFP), hen egg protein (HEP), grouper E. coioides juvenile protein (GJP) and red sea bream egg protein (REP), respectively. The highest WG and SGR were obtained in fish fed the control diet, followed by fish fed the diets with AA profiles of WFP and GJP. Fish fed the diets with AA profiles of BFP, REP and HEP showed relatively poor growth performance. Feed utilization showed a similar trend in growth parameters. Protein content of whole body among these treatments showed no significant differences (P > 0.05), but lipid content of whole body showed the highest value in the control group (P < 0.05). Dietary AA profiles significantly influenced plasma protein, cholesterol, triacylglycerol and glucose concentrations (P < 0.05). Dietary AA profiles significantly influenced the condition factor, hepatosomatic index and intraperitoneal fat ratio (P < 0.05).

Do dietary amino acid profiles affect performance of larval gilthead seabream?

Received 8 January 2007; Accepted 6 June 2007 Abstract - Live preys commonly used in fish larval rearing seem to be imbalanced in terms of amino acids. Manipu- lation of their amino acid composition is difficult, but the use of microencapsulated diets allows this manipulation. This study analysed the effect of amino acid supplementation, in order to compensate for dietary amino acid imbalances, on growth and survival of gilthead seabream (Sparus aurata) larvae. Larvae were reared until 32 days after hatching, in a closed recirculating water system (19 ◦ C), using only live food (rotifers and Artemia). Thereafter, larvae were fed Artemia or one of the experimental microencapsulated diets: supplemented with indispensable amino acids (IAAsup diet), or supplemented with dispensable amino acids (DAAsup diet). Experiment lasted for 10 days. Dietary supple- mentation with indispensable amino acids resulted in A/E ratios ((each indispensable amino acid) × (total indispensable amino acids) −1 × 1000) more similar to the ones of larval seabream and in higher IAA:DAA ratios than in the DAA- sup diet. Survival was similar in larvae fed the IAAsup diet (75%) or Artemia (87%), but was significantly lower in larvae fed the DAAsup diet (52%). Larvae from all treatments more than doubled their average dry weight during the experimental period. Final dry weight was similar in larvae fed both microcapsules, but these were lighter than larvae fed with Artemia. Relative growth rate (RGR) and total biomass production tended to be higher in larvae fed the IAA- sup (RGR = 9% day −1 ) than the DAAsup diet (RGR = 7.5% day −1 ) and only in this last treatment these parameters were significantly lower than in larvae fed with Artemia. Therefore, dietary supplementation with indispensable amino acids resulted in a more balanced dietary amino acid profile, which significantly increased survival. Further studies introducing microdiets earlier in the development seem necessary in order to optimise growth.

Evaluation of pea protein isolate as alternative protein source in diets for juvenile tilapia (Oreochromis niloticus)

To evaluate isolated pea protein as feed ingredient for tilapia (Oreochromis niloticus) juveniles, triplicate groups were fed with four isonitrogenous [crude protein: 421.1–427.5 g kg−1 in dry matter (d.m.)] and isoenergetic (gross energy: 20.46–21.06 MJ kg−1 d.m.) diets with varying protein sources for 8 weeks. Fish meal-based protein content of diets was substituted with 0% (diet 100/0=control group), 30% (diet 70/30), 45% (diet 55/45) and 60% (diet 40/60) isolated pea protein. Tilapia juveniles with an initial body weight of 2.23–2.27 g were fed in average at a level of 5% of their body weight per day. Highest individual weight gain (WG: 21.39 g) and specific growth rate (SGR: 4.21% day−1) and best feed conversion ratio (FCR: 0.90) were observed in tilapia fed diet 100/0, followed by fish-fed diet 70/30 (WG: 19.09 g; SGR: 4.03% day−1; FCR: 0.98), diet 55/45 (WG: 16.69 g; SGR: 3.80% day−1; FCR: 1.06) and diet 40/60 (WG: 16.18 g; SGR: 3.74% day−1; FCR: 1.06). Although fish fed diet 100/0 showed the best performance, inclusion of 30% protein derived from pea protein isolate resulted in a growth performance (in terms of WG and SGR) that did not differ significantly from diet 100/0 in contrast to fish fed diet 55/45 and 40/60. Crude ash content in the final body composition of the experimental fish decreased with increasing dietary pea protein content, while crude protein and lipid content remained equal between the groups. Significant decreasing growth performance and body ash incorporation of tilapia at higher inclusion levels seem to be mainly related to the dietary amino acid profile and phytic acid contents.

Evaluation of bioavailability of individual amino acids in Diplodus puntazzo larvae: Towards the ideal dietary amino acid profile

The indispensable AA profile of fish carcass has been commonly used as a good indicator of fish amino acids requirements. Amino acids composition of the whole body tissue of Diplodus puntazzo was determined for the larval ages of 5, 9, 12, 17, 25 and 35 days after hatching (DAH). No significant differences were found during this species ontogeny for any indispensable amino acid although for dispensable amino acids, significant differences were found for glutamate and glutamine ( p = 0.003), aspartate and arparagine ( p = 0.027) and serine ( p = 0.027). In order to obtain the ideal dietary amino acid profile, bioavailability was determined using 15N-labelled rotifers together with GC-C-IRMS. High relative bioavailabilities were found for isoleucine, leucine and valine, meaning these amino acids are retained more efficiently. On the contrary, alanine, glutamate and aspartate presented a lower bioavailability when compared to lysine. Histidine appeared to be the first limiting amino acid at 4 days after hatching (DAH) when larvae were fed rotifers. At 12, 25 and 35 DAH the first limiting amino acid seemed to be threonine. Comparing amino acid profiles, with and without taking into account the relative bioavailability data, accentuated differences were found for methionine and leucine. Using larval amino acid profiles corrected with relative amino acid bioavailability enables an estimation of the ideal dietary amino acid profile for Diplodus puntazzo.

Dietary Lysine Requirement as Basis to Estimate the Essential Dietary Amino Acid Profile for Jundiá, Rhamdia quelen

Abstract The present study was designed to determine the optimal dietary lysine requirement for jundiá, Rhamdia quelen, fingerlings. Groups of 17 fish (1.4 ± 0.1 g) were stocked in 120‐L tanks and were fed semipurified diets (33% crude protein [CP] and 3500 kcal metabolizable energy) containing increasing concentrations of lysine (3.0, 4.0, 4.5, 5.0, 5.5, 6.0, and 6.5% CP). After 119 d, fish weight gain (WG), specific growth rate (SGR), feed intake and feed conversion (FC), apparent net protein utilization (ANPU), body composition (CP, fat, and ash), and vertebral collagen were determined. WG and SGR increased as dietary lysine concentration in protein increased up to 4.5%, reducing at 6.0 and 6.5% lysine. Fish that were fed the lowest lysine concentration presented the worst feed conversion (FC), which improved for fish fed with 4.5% or more lysine. Feed consumption followed the same trend as FC. The highest ANPU was observed in fish fed with 4.5% lysine. Fish fed diets containing 4.5, 5.0, and 5.5% lysine accumulated more body protein (P &lt; 0.05). Collagen vertebral concentration was significantly higher in fish fed with the 4.5% lysine diet. Dietary requirement for lysine was 4.5 or 5.1% depending on the statistical model used for estimation: broken line or polynomial regression, respectively. The requirements for the other essential amino acids were estimated on the basis of the ideal protein concept and were similar to the requirements for other fish species, except for isoleucine, leucine, treonine, and valine, which were higher for jundiá.

Can Atlantic salmon ( Salmo salar) grow on diets devoid of fish meal?

The present experiment tested whether Atlantic salmon accept, grow and utilise diets devoid of fish meal. Four diets were prepared, one reference diet in which 49% of the diet was fish meal and three diets not containing any fish meal. The amino acid composition in the test diets not containing fish meal was made similar to the reference diet by balancing with crystalline amino acids. All plant protein diets also contained 5% fish protein hydrolysate and, additionally, two diets were added with either stick water or squid hydrolysate in order to improve the palatability and thus feed acceptance. The experimental diets were fed to Atlantic salmon of 300 g body weight for a period of 3 months during which period no fish died. Fish fed the plant protein diets showed reduced feed intake as compared to fish fed the reference fish meal diet resulting in lower growth in the former. Feed conversion did not differ between treatments. Although the fish fed the fish meal diet showed higher growth than those fed the alternative three diets, protein accretion was not significantly different. In contrast, fat retention was significantly higher in the fishmeal treatment suggesting both a higher retention of dietary fat which was higher in the fish meal diet and a better utilisation of the dietary energy by salmon fed the vegetable diets due to a highly balanced dietary amino acid profile. The use of up to 10% crystalline amino acids in the diet increased the amino acid digestibility in the plant protein diets but utilisation of the dietary protein was not affected. The latter indicate that crystalline amino acids are utilised as well as protein bound amino acids at the level of 10% addition. Taking all together, particularly the diet containing squid hydrolysate might be an alternative to the fish meal diet in order to produce salmon.

Densidade óssea de frangos de corte alimentados com diferentes níveis de aminoácidos e cálcio durante a fase final de criação

Two experiments were carried out aiming at evaluating the effects of different dietary amino acid and calcium profiles on bone characteristics of two chicken strains (Avian Farms and Cobb) from 42 to 49 days of age. At the end of each experiment, two chickens of each replication were sacrificed and their tibiae were collected for analysis of bone characteristics: bone measurements (weight, length and thickness of the compact and spongy layers) and bone density (bone density). A total of 540 birds were used in each experiment, divided into fully randomized blocks with a 3 x 2 factorial scheme, that is, three amino acid profiles (methionine, lysine and threonine – 100, 125 and 150% of NRC recommendations, 1994) and two calcium levels (75 and 100% of NRC recommendations, 1994), with 30 birds per replication. There were not interactions between the two factors. The amino acid or calcium levels did not affect bone density and tibia variables in both strains.

Dietary fiber, amino acid, fatty acid and tocopherol contents of the edible seaweeds Ulva lactuca and Durvillaea antarctica

The nutritional composition of the edible seaweeds Durvillaea antarctica (frond and stem) and dried Ulva lactuca was determined, including the soluble (SDF), insoluble (IDF) and total (TDF) dietary fiber content, amino acid and fatty acid profiles along with tocopherols and tocotrienols (pro-vitamin E). Results show that U. lactuca contained 60.5 ± 1.5%, and D. antarctica frond and stem 71.4 ± 1.5% and 56.4 ± 0.4% of TDF, respectively. Levels for the different amino acids ranged from 0.7 ± 0.1 to 1508.4 ± 9.5 (mg/100 g protein) in U. lactuca, from 0.2 ± 0.0 to 2019.9 ± 5.2 (mg/100 g protein) in D. antarctica (stem), and from 0.3 ± 0.0 to 1052.6 ± 2.9 (mg/100 g protein) in D. antarctica (leaves). In the three seaweeds, the most abundant fatty acid was C18:1ω9 cis which in U. lactuca accounted for 27.42 ± 2.60%; in D. antarctica it was 25.36 ± 3.10% and 25.83 ± 2.52% in leaves and stem, respectively. In D. antarctica, γ-tocotrienol (651.7 ± 5.1 mg/kg), δ-tocopherol (245.9 ± 3.7 mg/kg) and α-tocopherol (179.4 ± 12.1 mg/kg) were determined in fronds, α-tocopherol (258.0 ± 7.2 mg/kg) was determined in stem. U. lactuca, showed a high γ-tocopherol level (963.5 ± 3.8 mg/kg).

Responses of growing Japanese quails (heavy body weight line) to graded levels of essential amino acid concentrations in diets with or without fishmeal

AbstractThe influence of dietary amino acid profile on growth and immune response was investigated in growing quails (n = 928) divided into 24 subgroups. Eight dietary treatments with four levels of essential amino acids (EAA), viz. 90, 100, 110 and 120% of NRC, each with or without fishmeal (FM), were formulated following a four (EAA levels) times two (protein type) factorial design. Each treatment was allotted to three replicates up to 5 weeks of age. After 5 weeks of age 10 quails were randomly sacrificed from each treatment to study the relative weight of immune organs. Live weight gain was significantly higher (P &lt; 0.05) in diets containing 120% EAA with or without FM and 110% EAA with FM during 0 to 21 days of age. However, live weight gain from 21 to 35 days of age was higher (P &lt; 0.01) in quails received diets containing 90% EAA with or without FM and 100% EAA without FM than in other dietary treatments. Live weight gain increased linearly (P &lt; 0.01) with the increase in EAA levels overall (0–35 days). Feed intake was higher (P &lt; 0.01) in diets with higher EAA levels (110 and 120%) from 0 to 21 days. The interaction of EAA and protein type influenced (P &lt; 0.05) feed intake from 21 to 35 days of age. There was linear decrease (P &lt; 0.01) in feed intake with the lowering of EAA level up to 100% during 0 to 35 days. Feed conversion ratio (FCR) was better (P &lt; 0.01) up to day 21 at higher EAA levels (110 or 120%) while during days 21 to 35 better FCR was calculated (P &lt; 0.01) in diet with low EAA levels (90 or 100%). FCR was improved in all vegetable protein diet in comparison with FM diet. Energy efficiency up to 21 days of age was better (P &lt; 0.01) at high EAA levels (110 and 120%), while thereafter better at low (P &lt; 0.01) EAA levels (90 and 100%). Protein efficiency improved linearly (P &lt; 0.01) with decreasing EAA level. Humoral (SRBC) and cellular (PHA‐P) immune response did not differ in response to EAA levels or protein type. Higher (P &lt; 0.01) relative weight of spleen was recorded at 100% EAA level, while the relative weight of thymus was higher in diet containing 110% EAA level without fishmeal. Copyright © 2005 Society of Chemical Industry

Ingredient classification according to the digestible amino acid profile: an exploratory analysis

This study aimed: 1) to classify ingredients according to the digestible amino acid (AA) profile; 2) to determine ingredients with AA profile closer to the ideal for broiler chickens; and 3) to compare digestible AA profiles from simulated diets with the ideal protein profile. The digestible AA levels of 30 ingredients were compiled from the literature and presented as percentages of lysine according to the ideal protein concept. Cluster and principal component analyses (exploratory analyses) were used to compose and describe groups of ingredients according to AA profiles. Four ingredient groups were identified by cluster analysis, and the classification of the ingredients within each of these groups was obtained from a†principal component analysis, showing†11 classes of ingredients with similar digestible AA profiles. The ingredients with AA profiles closer to the ideal protein were meat and bone meal 45, fish meal 60 and wheat germ meal, all of them constituting Class 1; the ingredients from the other classes gradually diverged from the ideal protein. Soybean meal, which is the main protein source for poultry, showed good AA balance since it was included in Class 3. On the contrary, corn, which is the main energy source in poultry diets, was classified in Class 8. Dietary AA profiles were improved when corn and/ or soybean meal were partially or totally replaced in the simulations by ingredients with better AA balance.

Dietary amino acids affect intestinal Clostridium perfringens populations in broiler chickens

An experiment was performed to examine the effect of protein source and dietary amino acid profile on intestinal levels of C. perfringens in broiler chickens. Broiler chickens (age = 14 d; n = 192) were fed diets containing 400 g kg-1 crude protein with fish meal, meat/bone meal, feather meal, corn gluten meal, soy protein concentrate, pea protein concentrate, or potato protein concentrate as the primary protein source along with a control diet containing 230 g kg-1 crude protein. The birds were orally inoculated daily, with 1 mL (~1.0 × 108 CFU mL-1) of an overnight culture of C. perfringens between 14 and 21 d of age, killed at 28 d of age and C. perfringens numbers in ileum and cecum were enumerated. Birds fed fish meal, meat/bone meal, feather meal and potato protein concentrate had significantly higher intestinal C. perfringens counts than the birds fed corn gluten meal, soy or pea protein concentrates or the control diet (P &lt; 0.05). The glycine content of the diets and ileal contents was significantly, positively correlated with C. perfringens numbers in ileum and cecum. Dietary glycine may be an important factor in the intestinal overgrowth of C. perfringens in broiler chickens. Key words: Clostridium perfringens, broiler chicken, amino acid, glycine, necrotic enteritis

Effects of supplementation of coated crystalline amino acids on growth performance and body composition of juvenile kuruma shrimp Marsupenaeus japonicus

Supplementation of crystalline amino acids (CAA) in shrimp diets is unsuccessful in most cases. In the present study, various pre-coated CAA were developed to minimize the leaching losses from diets in water and assessed using kuruma shrimp Marsupenaeus japonicus juveniles. Experimental diets were supplemented with coated CAA or non-coated CAA to simulate the dietary amino acid profile to that found in the whole body protein of shrimp. The four diets contained CAA coated with either carboxymethyl cellulose (CMC) (diet 1), zein (diet 2), k-carrageenan (diet 3) or agar (diet 4), respectively. Another four diets contained CMC-coated CAA with the addition of either zein (diet 5), casein-gelatin (diet 6), zein and k-carrageenan (diet 7), or casein-gelatin and k-carrageenan (diet 8), respectively. The 8 weeks feeding trial demonstrated that the diets containing coated CAA gave significantly higher weight gains than diets containing non-coated CAA, with the highest value for the diet 6. The diets containing coated CAA also yielded higher feed conversion efficiency, protein efficiency ratio, and specific growth rate than diets containing non-coated CAA. Leaching trials suggested that shrimp growth performance was improved partly due to the retardation or reduction of CAA leaching by coating them with specific binders.

Nutritional assessment of somatolactin function in gilthead sea bream ( Sparus aurata): concurrent changes in somatotropic axis and pancreatic hormones

The role of somatolactin (SL) in the regulation of energy homeostasis in gilthead sea bream ( Sparus aurata) has been analysed. First, a down-regulation of plasma SL levels in response to gross shifts in dietary amino acid profile and the graded replacement of fish meal by plant protein sources (50%, 75% and 100%) has been observed. Thus, the impaired growth performance with changes in dietary amino acid profile and dietary protein source was accompanied by a decrease in plasma SL levels, which also decreased over the course of the post-prandial period irrespective of dietary nitrogen source. Secondly, we examined the effect of SL and growth hormone (GH) administration on voluntary feed intake. A single intraperitoneal injection of recombinant gilthead sea bream SL (0.1 μg/g fish) evoked a short-term inhibition of feed intake, whereas the same dose of GH exerted a marked enhancement of feed intake that still persisted 1 week later. Further, we addressed the effect of arginine (Arg) injection upon SL and related metabolic hormones (GH, insulin-like growth factor-I (IGF-I), insulin and glucagon) in fish fed diets with different nitrogen sources. A consistent effect of Arg injection (6.6 μmol/g fish) on plasma GH and IGF-I levels was not found regardless of dietary treatment. In contrast, the insulinotropic effect of Arg was found irrespective of dietary treatment, although the up-regulation of plasma glucagon and glucose levels was more persistent in fish fed a fish meal based diet (diet FM) than in those fed a plant protein diet with a 75% replacement (diet PP75). In the same way, a persistent and two-fold increase in plasma SL levels was observed in fish fed diet FM, whereas no effect was found in fish fed diet PP75. Taken together, these findings provide additional evidence for a role of SL as a marker of energy status, which may be perceived by fish as a daily and seasonal signal of abundant energy at a precise calendar time.

Amino acid availability: aspects of chemical analysis and bioassay methodology

It is important to be able to characterise foods and feedstuffs according to their available amino acid contents. This involves being able to determine amino acids chemically and the conduct of bioassays to determine amino acid digestibility and availability. The chemical analysis of amino acids is not straightforward and meticulousness is required to achieve consistent results. In particular and for accuracy, the effect of hydrolysis time needs to be accounted for. Some amino acids (for example, lysine) can undergo chemical modification during the processing and storage of foods, which interferes with amino acid analysis. Furthermore, the modified amino acids may also interfere with the determination of digestibility. A new approach to the determination of available lysine using a modified in vivo digestibility assay is discussed. Research is required into other amino acids susceptible to structural damage. There is recent compelling scientific evidence that bacterial activity in the small intestine of animals and man leads to the synthesis and uptake of dietary essential amino acids. This has implications for the accuracy of the ileal-based amino acid digestibility assay and further research is required to determine the extent of this synthesis, the source of nitrogenous material used for the synthesis and the degree of synthesis net of amino acid catabolism. Although there may be potential shortcomings in digestibility assays based on the determination of amino acids remaining undigested at the terminal ileum, there is abundant evidence in simple-stomached animals and growing evidence in human subjects that faecal-based amino acid digestibility coefficients are misleading. Hindgut microbial metabolism significantly alters the undigested dietary amino acid profile. The ileal amino acid digestibility bioassay is expected to be more accurate than its faecal-based counterpart, but correction of the ileal amino acid flow for amino acids of endogenous origin is necessary. Approaches to correcting for the endogenous component are discussed.

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.

A balanced dietary amino acid profile improves amino acid retention in post-larval Senegalese sole ( Solea senegalensis)

The rearing of most marine fish larvae still relies on live food. Dietary amino acid (AA) imbalances when using live food in the larval rearing of flatfishes have been suggested. The aim of this study was to test if dietary AA supplementation affects AA metabolism in Senegalese sole ( Solea senegalensis) post-larvae. This was done by tube-feeding Artemia-fed sole with a dipeptide solution containing two potential limiting AA (leucine and phenylalanine), in order to supplement the larval gut content and to balance the dietary AA profile. Two experiments were done using different 14C-labelled AA as tracers. The first used a 14C-protein hydrolysate to test the effect of balancing the dietary AA profile on the overall AA metabolism. The second experiment analysed the effect of balancing the dietary AA profile on metabolism of three-selected AA: arginine, leucine and glutamate. A set-up to determine the handling of 14C-labelled AA was used, in order to quantify the absorption, catabolism and retention of the test mixtures by the sole post-larvae. The first experiment demonstrated that, when fish were fed the dipeptide supplement, AA catabolism decreased and AA retention increased. This agrees with the hypothesis that balancing the dietary AA profile increases AA retention in fish. In the second experiment, arginine and glutamate catabolism were reduced by the dipeptide supplementation. Leucine supplementation did not reduce leucine catabolism but instead increased arginine and glutamate retention. This result supports earlier studies that fish larvae are able to regulate their AA metabolism. A balanced dietary AA profile increases the AA retention and may improve growth and nitrogen utilisation.

Effects of dietary amino acid profile on growth performance, key metabolic enzymes and somatotropic axis responsiveness of gilthead sea bream (Sparus aurata)

Juvenile gilthead sea bream were fed to visual satiety with isonitrogenous diets based on fish meal and different plant ingredients (33–35% replacement) supplemented with free amino acids to meet the desired indispensable amino acid (IAA) profile and dispensable amino acid (DAA) content. In diets M and WB, IAA profile and DAA content resemble that of the muscle or whole body, respectively. In diets MGlu and WBGlu, DAA content was increased by adding l-glutamic acid (Glu) and thus the IAA/DAA ratio varied from 1.13 (diet M) to 0.80 (diet WBGlu). Growth rates were not significantly different among experimental groups, but feed conversion ratio and nitrogen retention were impaired by the decrease of dietary IAA/DAA ratio. Postprandial ammonia excretion increased with the increase of dietary DAA content irrespective of IAA profile. Conversely, hepatic activity of glutamate dehydrogenase (GDH) was lower in fish fed diet WBGlu than in fish fed diet M. Hepatic growth hormone (GH) binding was not significantly affected by the dietary treatment, but circulating levels of insulin-like growth factor-I (IGF-I) and GH were, respectively, down- and up-regulated in fish fed diet WBGlu, which suggests some defect in the transmission of GH receptor signal. Fat retention and hepatic activities of lipogenic enzymes (glucose-6-phosphate dehydrogenase, G6PD; malic enzyme, ME) were decreased in fish fed diet MGlu. Key metabolic enzymes of hepatic glycolysis (glucokinase, GK) and gluconeogenesis (phosphoenolpyruvate carboxykinase, PEPCK) were also altered in this group of fish. Since soybean meal concentration was highest in diet MGlu, results on lipid and carbohydrate metabolism can be primarily attributed to this component of the diet. In contrast, data on growth performance, ammonia excretion and GH axis mainly reflect changes in the dietary amino acid profile, which reveals that a muscle IAA profile and a high IAA/DAA ratio are important in feeds for gilthead sea bream.

Dietary Lysine Requirement of Juvenile Yellowtail Flounder Pleuronectes Ferrugineus

The lysine requirements of juvenile yellowtail flounder (Pleuronectes ferrugineus) having 19.5 g initial body weight were estimated by feeding six practical-type diets containing graded levels of lysine (1.21 to 2.69% of dry diet). Dietary amino acid profile simulated that of whole body of yellowtail flounder. Most of amino acids in the diets were provided by corn gluten meal, herring meal and gelatin. Protein efficiency ratio (PER) improved significantly until lysine level increased up to 2.1% (4.3% of protein). Same trend was observed in feed:gain ratio (FGR) which maintained constant in fish groups fed diets containing lysine above 2.1%. The highest nitrogen gain (0.34 g/fish) in whole body was found in fish fed 2.1% lysine, though the value was not different from those of fish fed above the level of lysine. Fish fed 2.1% lysine also showed the best nitrogen retention efficiency of 24.6%. The broken-line analysis of protein efficiency ratio and body nitrogen gain against dietary lysine level yielded an estimated lysine requirement of 2.2% (4.5% of protein) and 2.3% (4.7% of protein), respectively. (Asian-Aust. J. Anim. Sci. 2003. Vol 16, No. 12 : 1777-1781)