Total Essential Amino Acid Content Research Articles

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

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

Optimising Soymilk Protein Nutriture through Selection of Appropriate Processing Technique

A significant contributor to compromised nutriture of a particular nutrient is the method of processing or preparation. The pre-treatment technique employed in the processing of soybean milk is a wellrecognized factor that not only aids in the deactivation of certain anti-nutritional components but also enhances its protein digestibility and bioavailability. Second to the overall importance of soybean is the protein composition, which is a function of the monomeric amino acid it contains. Thus, the amino acid profile of soybean milk processed by three pretreatment methods including soaking, roasting and boiling was analyzed using amino acid analyzer (model 120A PTH; Applied Biosystems, Thermo Fisher Scientific, USA). The results show that pretreatment by boiling retained the best product judged in terms of general nutritional quality as shown by higher total amino acid content recorded as 97.95g/100g compared to those of toasted and soaking which were 88.36 g/100g and 91.28 g/100g respectively. Also boiling technique recorded the highest total essential amino acid content of 51.01g/100g as against 46.58g/100g and45.85g/100g for toasting and soaking methods employed. In the same vein, boiling technique gave the highest amount of total conditional amino acids, which was 46.37g/100g when compared to that of toasting at 43.18g/100g) and soaking at 42.26g/100g, making it ideal for therapeutic purposes. This findings show that soymilk produced through boiling pretreatment is recommended for consumption at both household and commercial levels in order to optimize the full benefit of soymilk nutrition and therapeutics.

Effect of temperature on chemical properties and antioxidant activities of abalone viscera subcritical water extract

The effect of temperature on the main components and antioxidant activities of abalone viscera subcritical water extract (AVSWE) was investigated. With the increase in temperature from 110 °C to 230 °C, the protein content in AVSWE increased from 57.4% to 68.5%, while the carbohydrate content decreased from 17.9% to 0.8%. The highest percentage of 1000–5000 Da peptide fraction and total essential amino acid content was found in the AVSWE extracted at 170 °C. The transformation rate of arsenobetaine into dimethylarsinic acid in AVSWE increased dramatically with the increase subcritical water temperature from 170 °C to 200 °C. The results of DPPH and hydroxyl radical scavenging activity, reducing power and lipid peroxidation inhibition effect showed that AVSWE with the highest antioxidant activities was extracted at 170 °C. However, the subcritical water temperature for AVSWE extraction should not exceed 140 °C according to arsenic speciation.

Effect of Traditional Processing on the Nutritional Quality and in vivo Biological Value of Samh (Mesembryanthemum forsskalei Hochst) Flour.

Roasting improved the determined protein and carbohydrate content of the flour compared to raw flour (p < 0.05). Baking enhanced the determined moisture and ash content of the flour compared to all treatments (p < 0.05). Similar amino acid content was found in both raw and treated flours with glutamic acid, glycine, arginine, and aspartic acid being predominant. Cooking reduced the total aromatic and non-essential amino acid content whereas roasting reduced the total essential amino acid content of samh flour. All treatments significantly (p < 0.05) decreased the antinutritional factors compared to untreated raw flour. Baking decreased the trypsin inhibitor activity by almost 98.7% whereas cooking reduced phytate and tannin content by 38.5% and 10.8, respectively. Roasting and baking significantly (p < 0.05) improved the in vitro protein digestibility of the flour. In vivo, the true faecal nitrogen digestibility of rats was significantly (p < 0.05) enhanced by all treatments. Baking and cooking increased (p < 0.05) the net protein utilization and biological value of the flour. Overall, the treatments improved the nutritional quality of samh flour.

Impact and consequences of dietary riboflavin deficiency treatment on flesh quality loss in on-growing grass carp (Ctenopharyngodon idella).

Fish is among the cheapest and most promising sources of animal protein. The main edible portion of fish is muscle. This study explored the impact of dietary riboflavin on fish flesh quality and showed the possible role of muscle antioxidant defense in flesh quality in relation to dietary riboflavin. On-growing grass carp (initial average weight of 275.82 ± 0.57 g) were fed diets containing graded levels of riboflavin (0.63, 1.95, 3.98, 6.02, 7.96, and 10.04 mg kg-1 diet) for eight weeks. The results indicated that compared with the optimal riboflavin levels (3.98 and/or 6.02 mg riboflavin per kg diet), riboflavin deficiency treatment (0.63 mg riboflavin per kg diet) significantly reduced the muscle nutrients, including the protein, lipid, flavor amino acid, and total essential amino acid contents. Furthermore, the muscle shear force, pH value, and hydroxyproline concentration were reduced, while the muscle cooking loss and lactic acid content increased (P < 0.05). Compared with optimal riboflavin levels, the riboflavin deficiency treatment increased the reactive oxygen species (ROS), malondialdehyde (MDA), and protein carbonyl contents, while riboflavin treatments of 3.98-10.04 mg riboflavin per kg diet showed the lowest ROS and MDA contents (P < 0.05). Compared with the optimal riboflavin levels, the riboflavin deficiency treatment decreased the activities of copper/zinc superoxide dismutase (CuZnSOD), glutathione reductase (GR), catalase (CAT), and glutathione peroxidase (GPx), and reduced the glutathione (GSH) content (P < 0.05). Furthermore, the relative mRNA levels of antioxidant enzymes, including CuZnSOD, CAT, GR and GPx, and antioxidant-related signaling molecules, including NF-E2-related factor 2 (Nrf2) and casein kinase 2, were down-regulated, while those of Kelch-like ECH-associated protein 1b were up-regulated (P < 0.05). Collectively, the present study indicates that riboflavin deficiency treatment reduces the flesh quality, partly due to inhibition of the antioxidant defense through the Nrf2 signaling pathway, while optimal riboflavin levels reverse these negative effects.

Nutritional Properties of Various Tissues from New Kenaf Cultivars

Kenaf is an economically important crop that contains various functional compounds. The objective of this study was to evaluate the nutritional properties of leaves, stem bark, flowers, and seeds collected from three mutant kenaf cultivars (Jangdae, Baekma, and Jeokbong) and two original cultivars (Jinju and C14). For all analyzed tissues, there were no significant differences in the proximate compositions (moisture, crude protein, crude fiber, crude fat, ash, and nitrogen-free extract) among the tested genotypes, except for the leaf crude protein content, which was highest in Jinju plants. Of the tested minerals, potassium and calcium were the most abundant in all tissues. Additionally, we detected significant differences in the mineral contents (e.g., calcium, phosphorus, potassium, magnesium, zinc, and iron) of various tissues in all cultivars. Proline and phenylalanine were the major amino acids detected in leaves, and the highest total amino acid (TAA) and essential amino acid (EAA) contents were observed in Jinju plants. The TAA and EAA contents were lower in stem bark than in the other tissues, except in Baekma plants, in which the lowest levels were observed in flowers. Moreover, the TAA and EAA contents were approximately 20 times lower in white flowers (Baekma) than in ivory flowers. Furthermore, the highest TAA and EAA concentrations were observed in Jangdae seeds. These results may be useful for identifying the optimal cultivar and tissues for use in food products.

Nutritive and Biological Value of Liver and Blood of Various Slaughtered Animals

Offal, such as liver, heart, tongue, kidneys, blood, skin, bone, etc., represents an essential source of protein, vitamin and mineral elements. The present study is an attempt at determining the amino acid composition of horse and beef liver and blood. In general, horse liver was to be a good source of protein (25.06%) compared with beef liver (17.4%). The moisture (74.9%) and fat (3.8) contents were significantly higher (p<0.05) in beef liver, while the ash content of the horse liver was 1.42% compared to 1.30% in beef liver. Total essential amino acid content was higher in beef liver (40.63%) than in horse liver (37.31%).

Nutritivni i fenolni profil male jestive gljive Coprinellus disseminatus (pers.) J.E. Lange 1938

The aim of this work was to investigate nutritional profile in relation to proteins, amino acids, fatty acids and mineral composition, as well as phenolic profile of small edible fungal species Coprinellus disseminatus originated from Serbia. Total protein content in the analyzed fungal species was 9.72%. Fifteen protein fractions obtained by electrophoresis were identified in a range from 1.6 to 63.6 kDa. Chip-based separations showed the presence of protein fraction with molecular weight of 27.5 kDa that could possess antifungal activity. The total essential and non-essential amino acid contents were 29.57 and 96.69 mg/g DW, respectively. Among the essential amino acids, leucine was the most abundant. Fatty acid composition of C. disseminatus showed that polyunsaturated fatty acids (PUFA, 59.1% of total FA) predominated over saturated fatty acids (SFA, 23.1% of total FA) and monounsaturated fatty acids (MUFA, 17.9% of total FA). The dominant fatty acids were linoleic acid (56.6%), palmitic acid (13.9%), and oleic acid (12.0%). The most abundant macroelement in C. disseminatus was potassium, followed by calcium and magnesium, while iron dominated in microelements. Eight phenolic compounds were quantified in methanolic extract of C. disseminatus by LC-MS/MS with the highest amount of p-hydroxybenzoic acid and p-coumaric acid reaching 9.46 ± 0.2 µg/g DW and 7.8 ± 0.1 µg/g DW, respectively.

Biochemical Composition of Pond-Cultured vs. Wild Gravid Female Mud CrabScylla paramamosainin Hainan, China: Evaluating the Nutritional Value of Cultured Mud Crab

Mud crab (MC) aquaculture is rapidly developing fast worldwide, and there is a high consumer demand for Scylla paramamosain. Demand for MCs is especially high in China, where such crabs, especially the gravid females, are regarded a delicacy. In Hainan Island, pond-rearing wild MC juveniles in the presence of local trash fish and shrimps in brackish water has been shown to be successful. The nutritional value of cultured MC, however, has not been evaluated. In this paper, the biochemical composition of pond-cultured and wild gravid female MCs was studied. The cultured MCs had a higher ratio of total edible yield than the wild ones. The contents of crude protein and crude lipid in the cultured MCs were significantly lower than in the wild MCs (P < 0.05). Furthermore, the total amino acid (TAA) and essential amino acid (EAA) contents of gonads in the wild MCs were both significantly higher than those in the cultured MCs (P < 0.05). The TAAs and EAAs of claw and body muscles in cultured MCs, however, were significantly higher (P < 0.05). There were no significant differences in the contents of polyunsaturated fatty acids (PUFAs), n-3 fatty acids, and n-6 fatty acids in the gonad of bothMCgroups, whereas the contents of total saturated fatty acids (SFAs) and monounsaturated fatty acids (MUFAs) were significantly different between the wild and the cultured MCs (P < 0.05). Furthermore, there were no significant differences in the contents of SFAs, MUFAs, and PUFAs in both claw and body muscle between the wild and cultured MCs.

Amino Acid, Amino Acid Metabolite, and GABA Content of Three Domestic Tomato Varieties

To determine the nutritional value of domestic tomatoes, the levels of amino acids, amino acid metabolites, and the bioactive compound γ-aminobutyric-acid (GABA) were analyzed in three domestic tomato varieties (Rafito, Momotaro, and Medison). Eighteen free amino acids were found, and total free amino acid content was 3,810.21～4,594.56 mg/100 g (dry weight). L-glutamic acid (L-Glu) was the most abundant amino acid, ranging from 1,866.60 mg/100 g for Momotaro to 2,417.45 mg/100 g for Medison. The next most abundant amino acids were L-glutamine (L-Gln) and L-aspartic acid (L-Asp). The three tomato varieties had a good balance of all the essential amino acids except tryptophan. Total essential amino acid content was 274.26～472.71 mg/100 g (dry weight). The following amino acid metabolites were found: L-carnitine (L-Car), hydroxylysine (Hyl), o-phosphoethanolamine (o-Pea), phosphoserine (p-Ser), β-alanine (β-Ala), N-methyl-histidine (Me-His), ethanolamine (EtNH2),and L-citrulline(L-Cit). Large quantities of GABA were found in all three varieties: 666.95-868.48 mg/100g (dry weight). These results support the use of these tomato varieties as nutritious food materials.

Dietary supplementation of Lonicera macranthoides leaf powder improves amino acid profiles in serum and longissimus thoracis muscle of growing-finishing pigs.

A 60-days feeding trial was conducted to determine the effect of dietary supplementation of Lonicera macranthoides leaf (LML) on growth performance, meat quality, and free amino acid profiles in growing-finishing pigs. L. macranthoides leaves were harvested, air-dried and milled to powder. A total of 288 crossbred barrows (Large White × Landrace) with an average initial BW of 54.0 ± 3.4 kg were randomly allocated to 3 treatment groups and fed either a basal diet or a diet supplemented with 0.5% or 1.0% LML powder. Results showed that diet supplemented with LML powder did not affect average daily feed intake (ADFI) and feed: gain ratio (P > 0.05) in growing-finishing pigs. Moreover, diet supplemented with LML powder showed no significant effects on carcass traits (P > 0.05) including dressing percentage, backfat thickness and loin muscle area, and meat quality traits (P > 0.05) including meat color, intramuscular fat and cooking loss. However, diet supplemented with LML powder significantly improved free amino acid profiles in serum and longissimus thoracis muscle in growing-finishing pigs. Most importantly, dietary LML powder increased total free amino acids content (P < 0.001) and essential free amino acid content (P < 0.001) in longissimus thoracis muscle. These results indicate that LML has the potential to improve the nutritional value of meat through improving free amino acid profiles.

A comparison on the nutritional quality of proteins from Moringa oleifera leaves and seeds

AbstractThe aim of this study was to evaluate the nutritional quality of protein from Moringa oleifera seeds and leaves. The defatted flours were rich in protein (33.53 and 18.63% for seeds and leaves, respectively) and carbohydrates. Amino acid analysis revealed the presence of all essential amino acids in both leaf and seed flour, with high content of leucine and valine and low content of methionine and cysteine. The total essential amino acids content of leaf flour (42.76 g/16 g N) was higher than that of seed flour (35.07 g/16 g N). Limiting amino acids were lysine and sulfur amino acids. The available lysine content of leaf flour (3.78 g/16 g N) was significantly higher than that of seed flour (1.30 g/16 g N). In vitro digestibility studies revealed that leaf proteins were more easily digested by pepsin than seed proteins. Moreover, after a pepsin-pancreatin hydrolysis, digestibility of seed flour (61.12%) was significantly higher than that of leaf flour (57.22%). In addition, the leaf flour showed h...

Effect of Long-term Application of Chemical Fertilizer on the Quality of Summer Maize

The study on the effect of fertilization on the quality of maize grain was conducted based on continue application of fertilizer for 26 and 36 years in gleyic cambisols. The amounts of protein, starch, fat and amino acid were determined and the amino acid was analyzed by cluster analysis. The results showed: Long-term fertilization 26 years showed that N2K and N2P processing protein content as high as 9.01, 9.01%, lowest comparing CK treatment is 5.52%; all fertilizer treatments reduced the summer maize starch content, including N2PK deal with relatively high starch content is 57.55%; N2K processing crude fat content as high as 5.95%; N2P processing total amino acids and essential amino acid content is the highest, 8.13 and 3.22%, respectively. Long-term fertilization 36 years (2013) summer maize grain each nutrition indicators in line with 26 years change rule.

Meta-analysis of the amino acid digestibility of oilseed meal in growing pigs

Oilseed meal is an important source of essential amino acids (EAA) for livestock production. It is the second most important ingredient in pig feed after grains. Optimal use of these ingredients requires precise knowledge of amino acid standardized ileal digestibility (SID), which may vary depending on several factors including botanical variety or processing treatments. A meta-analysis was performed in order to derive models for predicting the SID of soybean, cotton and rapeseed meal EAA, based on chemical composition data such as CP, total concentration of each EAA and fibre (crude fibre, ADF and NDF) content. A database of 47 references (224 experimental treatments) was built. A model incorporating processing method of the meals (e.g. cold pressed, expeller pressed, solvent extracted), experimental surgical procedure (T-cannula, re-entrant cannula, post valve T-cannula and ileo-rectal anastomosis) and pig growth stage (BW⩽ or ⩾25 kg) was tested. Results indicated that neither processing nor BW affected EAA SID. NDF was the best predictor of SID (R2=0.944, 0.836, 0.779, 0.899 and 0.814, respectively, for Lys, Met, Thr, Trp and Val). The total EAA content was the best predictor of digestible content (g/kg diet) for each EAA (R2=0.990, 0.985, 0.977, 0.985 and 0.978, respectively, for Lys, Met, Thr, Trp and Val). This study shows that routine chemical analyses may be used to predict EAA digestibility with satisfactory accuracy.

Quality Characteristics of New Reddish Brown Color Rice Variety “Superhongmi”

전통적인 교배육종을 통하여 총 폴리페놀 함량을 높인 슈퍼홍미(흑진주벼/수원 425호//대립벼 1호)벼 품종(품종출원 2015-339호)의 작물학적 특성과 품질특성을 조사 분석한 결과를 요약하면 다음과 같다. 슈퍼홍미벼 품종의 평균출수기는 9월 5일로 만생종이며, 간장은 94.7 cm 정도이며 임실률은 81.7%였다. 또한 현미천립 중은 26.8 g 정도로 슈퍼자미(26.2 g)보다 무거운 품종이다. 슈퍼홍미벼 품종은 다른 유색미 품종보다 기름함량과 단백질 함량이 낮았다. 그리고 불포화지방산인 올레산, 리놀레산 함량이 높았다. 공시 유색미품종의 필수아미노산 함량은 현미 100 g 당 슈퍼홍미 6695.13 mg, 슈퍼자미 6898.28 mg으로서 비슷하였으며, 필수아미노산 중에서 슈퍼홍미 품종은 tyrosin과 arginine은 높은 것으로 평가되었다. 슈퍼홍미벼 품종의 총 폴리페놀함량은 248.31 mg으로서 동진벼 보다 6배, 흑진주벼 보다 2배 높았다. 플라보노이드 함량은 동진벼 보다 8배, 흑진주벼 보다 2배 높았다. 슈퍼홍미의 hydroxy radical 소거능은 동진벼 보다 높은 활성을 나타내는 것으로 확인되었다. 그러나 유색미 간의 hydroxy radical 소거능은 유의적인 차이는 보이지 않았다. 따라서, 슈퍼홍미는 식량으로서 뿐만 아니라 다양한 기능성 식품소재로서 높은 가치가 있는 것으로 기대된다. 'Superhongmi' is a new rice variety with reddish brown color developed from a crossing a high cyanidin 3-glucoside (C3G) content beeeds including Heugjinju and Suwon 425 and a big grain size breed such as Daeribbyeo. This variety heads on Sep. 5 and has 86.7 cm culm length. The fertility ratio of Superhongmi was about 81.7% and weight of 1,000-grain was about 26.8 g. The 1,000 grain weight of Superhongmi was heavier than that of Superjami. The total essential amino acid content of Superhongmi was lower than those of others. However, Superhongmi was high in tyrosine and arginine. Total polyphenol content of Superhongmi was 2 times higher than that of Heugjinju and flavonoid content was 8 times higher than that of Dongjinbyeo. In addition, hydroxy radical scavenging activity of Superhongmi was significantly higher than that of Dongjinbyeo. However, significant differences were not found in the newly breed colored rice. These results suggest that Superhongmi variety has very high value as a source of various functional food as well as stable food.

Dietary arginine requirement of juvenile swimming crab,Portunus trituberculatus

An 8-week feeding trial was conducted to determine the optimal dietary arginine requirement for juvenile swimming crab Portunus trituberculatus. Six isonitrogenous and isolipidic experimental diets were formulated to contain graded arginine levels which ranged from 15.9 to 33.0 g kg−1. Each diet was randomly assigned to triplicate groups of 60 juvenile swimming crabs (4.72 ± 0.12 g). The results indicated that dietary arginine had significant effects on weight gain (WG), specific growth rate (SGR), protein productive value, feed efficiency and protein efficiency ratio. Weight gain and SGR significantly increased with the dietary arginine increasing from 15.9 to 27.4 g kg−1, while with the further increasing from 27.4 to 33.0 g kg−1, WG and SGR did not increase significantly. Maximum arginine, proline and total essential amino acid contents in muscle were observed in 27.4 g kg−1 group diet. The swimming crab fed the diet with lower dietary arginine level showed higher AST and lower ALT in the serum. Crab fed with the lower dietary arginine level had significantly lower ALT in the serum than the other groups. Haemolymph indexes were significantly affected by the dietary arginine level except for the cholesterol concentration, and the highest values were all found in 27.4 g kg−1 group diet. The two slope broken-line model using SGR showed that the optimal dietary arginine requirement was 27.7 g kg−1 of the dry matter (56.0 g kg−1 dietary protein) for juvenile swimming crab.

Breadfruit (Artocarpus altilis): a source of high-quality protein for food security and novel food products.

Protein deficiency has been observed as a leading cause of malnutrition and child death in the tropics. The current study evaluated the protein quality of 49 important breadfruit cultivars (41 Artocarpus altilis and 8 hybrids of A. altilis×A. mariannensis). While significant differences were found between cultivars, all varieties contained a full spectrum of the essential amino acids and are especially rich in phenylalanine, leucine, isoleucine, and valine. The cultivar Ma'afala contained significantly higher total essential amino acid content than other varieties and higher-quality protein than staples such as corn, wheat, rice, soybean, potato, and pea.

Amino Acid Profiles of Some Varieties of Rice, Soybean and Groundnut Grown in Ghana

Amino acid profiles of some Ghanaian varieties of rice, soybean and groundnut were investigated to augment existing data on their physicochemical properties and provide information to guide their application in weaning foods formulation. Five varieties of rice and four varieties each of groundnuts and soybeans were analyzed. Amino acids were separated using HPLC. Without postcolumn derivatization, Evaporative Light Scattering Detector (ELSD) was used to determine their concentrations against standard amino acids. Local rice varieties lacked tryptophan, valine, glycine, glutamic acid and lysine and histidine was present in only Nerica-2 variety but Nerica-1 variety had the highest total essential amino acid content of 36.42 g/kg. Quarshie soybean variety expressed all the amino acids under study and also had the highest total essential amino acids content of 169.14 g/kg. Sinkarzie and F-Mix groundnut varieties expressed all amino acids except tryptophan, with Sinkarzie having the highest total essential amino acids content of 100.62 g/kg.

The Investigation of Virginiamycin-Added Fungal Fermentation on the Size and Immunoreactivity of Heat-Sensitive Soy Protein

The usage of soy protein for young monogastric animals is restricted due to potential allergens and high molecular weight. The investigation of fungi fermentation effect on soy protein has been interrupted by substrate sterilization. Virginiamycin at 0.05% was added together withAspergillus oryzaefor solid state fermentation (SSF) in unsterilized soy meal (SM). When compared toA. oryzaeSSF alone, virginiamycin did not cause the interference of fungal fermentation but elucidated the protein degradation. SDS-PAGE results showed that bothαandα′ subunits ofβ-conglycinin were degraded significantly. In addition, western blot results showed that the immunoreactive signals of soy protein were considerably reduced in virginiamycin-added fermentation with unsterilized SM. Furthermore, fungal fermentation increased total protein and essential amino acid contents, suggesting the value enhancement of SM products. Taken together, this study demonstrated for the first time that virginiamycin could help investigate fermentation effect on heat-sensitive soy protein. Fermented SM has several potential applications in feed industry.

Dietary methionine requirement of juvenile blunt snout bream (Megalobrama amblycephala) at a constant dietary cystine level

A 9-week feeding trial was conducted to investigate the dietary methionine requirement of juvenile Megalobrama amblycephala at a constant dietary cystine level. Six semipurified diets were formulated to contain graded dietary methionine levels from 3.9 to 15.4 g kg−1 in about 2.5 g kg−1 increments in the presence of 2.2 g kg−1 cystine. Results showed that specific growth rate (SGR) and protein efficiency ratio (PER) significantly increased with increasing dietary methionine levels from 3.9 to 12.4 g kg−1 and thereafter kept stable. Maximum protein productive value (PPV), nitrogen retention efficiency (NRE) and liver weight were observed in 8.5 g methionine kg−1 diet. Protein contents in whole fish body were positively correlated with dietary methionine level, while lipid contents were negatively correlated with it. Morphological index and hepatic glutamate-pyruvate transaminase (GPT) activities were independent of dietary methionine levels. However, dietary methionine supplementation significantly improved haematological parameters, plasma methionine and total essential amino acid contents and hepatic glutamate-oxaloacetate transaminase (GOT) activities. Analysis of dose response using broken-line regression on the basis of SGR and PPV versus dietary methionine level estimated the optimum dietary methionine requirements of juvenile M. amblycephala to be between 8.5 and 8.4 g kg−1 of diet (25.0 and 24.7 g kg−1 of protein) in the presence of 2.2 g kg−1 cystine, respectively. Hence, the corresponding total sulphur amino acids requirements of this species were calculated to be 10.7 and 10.6 g kg−1 of diet (31.5 and 31.2 g kg−1 of dietary protein).