Indispensable Amino Acid Requirements Research Articles

Consideration of insects as a source of dietary protein for human consumption.

Consumption of sufficient dietary protein is fundamental to muscle mass maintenance and overall health. Conventional animal-based protein sources such as meat (ie, beef, pork, lamb), poultry, fish, eggs, and dairy are generally considered high-quality sources of dietary protein because they meet all of the indispensable amino-acid requirements for humans and are highly digestible. However, the production of sufficient amounts of conventional animal-based protein to meet future global food demands represents a challenge. Edible insects have recently been proposed as an alternative source of dietary protein that may be produced on a more viable and sustainable commercial scale and, as such, may contribute to ensuring global food security. This review evaluates the protein content, amino-acid composition, and digestibility of edible insects and considers their proposed quality and potential as an alternative protein source for human consumption.

Dietary histidine requirement and physiological effects of dietary histidine deficiency in juvenile red drum Sciaenop ocellatus

In order to develop nutritious and cost-effective diets, the amino acid requirements of cultured fish species must be quantified. Several indispensable amino acid requirements of red drum Sciaenops ocellatus have already been reported; however, its requirement for histidine (His) has yet to be quantified. The aims of the present studies were to determine the minimum dietary His requirement of juvenile red drum and the physiological effects of His deficiency. A basal diet was prepared using lyophilized red drum muscle as an intact protein (10.5% of dietary protein) supplemented with crystalline amino acids (excluding His) to provide a total of 35% crude protein (CP) in the diet. Five isonitrogenous and isoenergetic experimental diets were prepared by supplementing the basal diet (0.3g His/100g dry diet) with increasing amounts of His (0.5, 0.7, 0.9, 1.1, 1.3g/100g dry diet). These diets were fed to triplicate tanks of juvenile red drum (initial average weight of 0.98±0.08g/fish) for 6weeks in feeding trial 1 to quantify the minimum dietary His requirement. His level had significant effects on relative weight gain, feed efficiency ratio, protein efficiency ratio, and plasma free His. According to quadratic broken-line regression on relative weight gain percentage, the dietary His requirement was 0.59 (±0.15) g/100g dry diet (1.6% of CP). Feeding trial 2 was performed to further examine His deficiency in red drum. In that trial, the basal diet and a His-supplemented diet (~1.2g/100g dry diet) were fed to juvenile red drum (initial average weight of 1.53±0.08g/fish) in triplicate tanks for 8weeks. Cataracts were found in 16.7% of eyes from fish fed the basal diet while no fish in the supplemented group developed cataracts. His-supplemented fish were found to have higher erythrocyte fragility than those fed the basal diet. Based on these results, the His requirement of red drum was defined and His deficiency was observed to affect blood parameters and increase the possibility of cataract development.

Amino Acid Requirements of Gilthead Bream (<i>Sparus aurata</i>) Juveniles

In one trial 120 gilthead bream fingerlings received tow different feed mixtures containing two different levels of protein (diet A.400 and B 360 gkg-1). The average initial live weight was about 2.2 ±0.1 g fish-1 in each replicate of all treatments. Twenty fish per aquarium were stocked randomly in 6 glass aquaria (120 l each). Fish were fed with experimental diets at rate 8 % of the body weight daily. The amino acids (AA) content was in the diets, whole fish and muscle at the end of the growth period (60 days). The results indicated that, at the end of experiment Sea bass fry had reached an average live weight 18.5 and 16.2 g fish-1 for fish fed diet A and B respectively. Also the increase of protein levels in the feed to 40% caused a significant decrease in the content of indispensable amino acid (IAA) and dispensable amino acid (as %v of whole fish and muscle of wet weight). Tow methods were subsequently used to estimate the quantitative IAA requirements of Sea bass fry based on the hypothesis that (a) the dietary requirement pattern of IAA reflects the tissue pattern and (b) the rate of daily deposition in the fish can be equated with the dietary requirement as percentage of 100 g-1 diet. The quantitative IAA requirement (%) of Sea bass (Dicentrarchus labrax) diets as follow: Lysine 2.27, Methionine 1.09, Therionine 0.61, Leucine 2.4, Isoleucine 0.47, Histidine1.6, Arginine 1.39, Phenylalanine 1.43, Valine 1.22 and Tryptophane 0.42.

Protein quality as determined by the Digestible Indispensable Amino Acid Score: evaluation of factors underlying the calculation.

The Food and Agriculture Organization of the United Nations recently recommended the adoption of a new and improved scoring system (Digestible Indispensable Amino Acid Score [DIAAS]) to quantify dietary protein quality. The DIAAS is based on the relative digestible content of the indispensable amino acids (IAAs) and the amino acid requirement pattern. Factors involved in calculation of the DIAAS include: use of the content and profile of IAAs as the basis for quality; methods for determination of the protein and amino acid content of the protein source; accuracy of individual requirement values for IAAs; normalization of IAA requirements by the estimated average requirement for protein; and basing the DIAAS on the true ileal digestibility of each IAA in the test protein. This review outlines the rationale for including each of these factors in the calculation of the DIAAS and describes associated potential errors.

Protein and Amino Acid Requirements during Pregnancy

AbstractProtein forms an essential component of a healthy diet in humans to support both growth and maintenance. During pregnancy, an exceptional stage of life defined by rapid growth and development, adequate dietary protein is crucial to ensure a healthy outcome. Protein deposition in maternal and fetal tissues increases throughout pregnancy, with most occurring during the third trimester. Dietary protein intake recommendations are based on factorial estimates because the traditional method of determining protein requirements, nitrogen balance, is invasive and undesirable during pregnancy. The current Estimated Average Requirement and RDA recommendations of 0.88 and 1.1 g · kg−1 · d−1, respectively, are for all stages of pregnancy. The single recommendation does not take into account the changing needs during different stages of pregnancy. Recently, with the use of the minimally invasive indicator amino acid oxidation method, we defined the requirements to be, on average, 1.2 and 1.52 g · kg−1 · d−1 during early (∼16 wk) and late (∼36 wk) stages of pregnancy, respectively. Although the requirements are substantially higher than current recommendations, our values are ∼14–18% of total energy and fit within the Acceptable Macronutrient Distribution Range. Using swine as an animal model we showed that the requirements for several indispensable amino acids increase dramatically during late gestation compared with early gestation. Additional studies should be conducted during pregnancy to confirm the newly determined protein requirements and to determine the indispensable amino acid requirements during pregnancy in humans.

Amino Acid Requirements of Gilthead Bream (Sparus aurata) Juveniles

In one trial 360 gilthead bream fingerlings received two different feed mixtures containing two different levels of protein (diet A 400 and B 360 g?kg?1). The average initial live weight was about 2.2 ± 0.1 g fish?1 in each replicate of all treatments. Sixty fish per tank were stocked randomly in 6 fiberglass tanks (1 m3 each). Fish were fed with experimental diets at rate 8% of the body weight daily. The Amino Acids (AA) content was analyzed in the diets, whole fish and muscle at the end of the growth period (60 days). The results indicated that at the end of experiment gilthead bream fingerlings had reached an average live weight 18.5 and 16.2 g fish?1 for fish fed diet A and B respectively. Also the increase of protein levels in the feed to 40% caused a significant increase in the content of Indispensable Amino Acid (IAA) and dispensable amino acid (as %v of whole fish and muscle of wet weight). Two methods were subsequently used to estimate the quantitative IAA requirements of gilthead bream fry based on the hypothesis that (a) the dietary requirement pattern of IAA reflected the tissue pattern and (b) the rate of daily deposition in the fish could be equated with the dietary requirement as percentage of 100 g?1 diet. The quantitative IAA requirement (%) of gilthead bream (Sparus aurata) diets was as follow: Lysine 2.27, Methionine 1.09, Therionine 0.61, Leucine 2.4, Isoleucine 0.47, Histidine1.6, Arginine 1.39, Phenylalanine 1.43, Valine 1.22 and Tryptophane 0.42.

Effects of low-protein diets supplemented with indispensable amino acids on growth performance, intestinal morphology and immunological parameters in 13 to 35 kg pigs

The objective of this study was to determine if a moderate or high reduction of dietary CP, supplemented with indispensable amino acids (IAA), would affect growth, intestinal morphology and immunological parameters of pigs. A total of 40 barrows (initial BW=13.50±0.50 kg, 45±2 day of age) were used in a completely randomized block design, and allocated to four dietary treatments containing CP levels at 20.00%, 17.16%, 15.30% and 13.90%, respectively. Industrial AA were added to meet the IAA requirements of pigs. After 4-week feeding, blood and tissue samples were obtained from pigs. The results showed that reducing dietary CP level decreased average daily gain, plasma urea nitrogen concentration and relative organ weights of liver and pancreas (P<0.01), and increased feed conversion ratio (P<0.01). Pigs fed the 13.90% CP diet had significantly lower growth performance than that of pigs fed higher CP at 20.00%, 17.16% or 15.30%. Moreover, reducing dietary CP level decreased villous height in duodenum (P<0.01) and crypt depth in duodenum, jejunum and ileum (P<0.01). The reduction in the dietary CP level increased plasma concentrations of methionine, alanine (P<0.01) and lysine (P<0.05), and decreased arginine (P<0.05). Intriguingly, reducing dietary CP level from 20.00% to 13.90% resulted in a significant decrease in plasma concentration of IgG (P<0.05), percentage of CD3+T cells of the peripheral blood (P<0.01), also down-regulated the mRNA abundance of innate immunity-related genes on toll-like receptor 4, myeloid differentiation factor 88 (P<0.01) and nuclear factor kappa B (P<0.05) in the ileum. These results indicate that reducing dietary CP level from 20.00% to 15.30%, supplemented with IAA, had no significant effect on growth performance and had a limited effect on immunological parameters. However, a further reduction of dietary CP level up to 13.90% would lead to poor growth performance and organ development, associated with the modifications of intestinal morphology and immune function.

Growth Responses of Juvenile Red Drum Sciaenops ocellatus to Dietary Phenylalanine and Tyrosine Can Be Used to Calculate the Total Aromatic Amino Acid Requirement ,

A current priority in aquaculture is the replacement of fish meal with alternative feedstuffs to ensure the industry's sustainability. However, most alternative protein sources are deficient in at least 1 indispensable amino acid (IAA). Therefore, there is a critical need to establish refined estimates of IAA requirements of fish. The objectives of this study were to determine the total aromatic amino acid (TAAA) requirement (Phe + Tyr) and the Tyr replacement value for Phe in juvenile red drum Sciaenops ocellatus. The TAAA requirement was obtained by feeding juvenile red drum diets that contained incremental amounts of Phe (0.54, 0.84, 1.14, 1.44, 1.74, and 2.04 g/100 g dry diet) and a fixed concentration of Tyr. Because of the TAAA requirement obtained, a second feeding trial was conducted to determine the maximum Tyr replacement value for Phe when a control diet was prepared with an 80%:20% Phe-to-Tyr ratio (Phe:Tyr; 1.60 g Phe/100 g dry diet and 0.41 g Tyr/100 g), and 5 experimental diets were prepared by decreasing the inclusion of Phe and increasing the inclusion of Tyr (Phe:Tyr of 70%:30%, 60%:40%, 50%:50%, 40%:60%, and 30%:70%). Weight gain, the feed efficiency ratio, and the protein efficiency ratio increased 354%, 133%, and 134%, respectively, relative to that of fish fed the basal diet as the Phe concentration increased to 1.44 g/100 g of dry diet; at higher concentrations of Phe, no significant differences were found between treatments. Analysis of the weight gain data with a broken-line model estimated the TAAA requirement of red drum to be 2.10 g/100 g dry diet (1.69 g Phe + 0.41 g Tyr). The maximum Tyr replacement value for Phe was estimated at 40%:60% Phe:Tyr, because only fish fed the diet with a 30%:70% Phe:Tyr ratio had a significant reduction (42%) in growth performance. The TAAA requirement for maximum growth of juvenile red drum was estimated to be 2.10 ± 0.08 g/100 g dry diet. Moreover, Tyr can account for up to 60% of the TAAA requirement of juvenile red drum.

Protein Quality of Amaranth Grains Cultivated in Ethiopia as Affected by Popping and Fermentation

The effect of popping and fermentation on protein quality of three different varieties of amaranth grains cultivated in Ethiopia was evaluated. Total lysine content of the grains was higher than that of commonly available cereals but close to that of legumes. Methionine and cysteine contents in the grains were also higher than that found in cereal and legume proteins. Percentage of total indispensable amino acids, excluding tryptophan, was 43% - 49%, which was higher than WHO reference pattern (31%). Popping resulted in 36% and 37% reduction in total lysine and cysteine contents, respectively, whereas fermentation reduced cysteine, lysine and methionine contents by 16%, 20% and 20%, respectively. From the free amino acids, histidine was the major indispensable amino acid but threonine was not detected. During popping, all free amino acids, except threonine, were reduced. On the other hand, fermentation significantly increased (p < 0.01) most amino acids except arginine, which was significantly decreased (p < 0.01), and tyrosine and glutamic acid, for which no change was observed. Popping decreased in vitro protein digestibility (IVPD) by 8.3% - 17.1% while fermentation increased IVPD by 4.8% - 7.5%. Substitution of amaranth for wheat and/or maize during complementary food formulation could contribute much to the daily requirements of indispensable amino acids of young children.

Nutritive value of canned River Nile Crayfish (Procambarus clarkii) products

This study was carried out to utilize Crayfish (Procambarus clarkii) flesh to produce canned products i.e. control (with or without vegetables). To some extent, raw Crayfish meat contains high contents of protein (15.22%) and fat (1.29%). Canned Crayfish products have a high nutritional quality of protein and high nutritional value as indicated by the values of total indispensable amino acids (TIAAs), Indispensable amino acids index (IAAsI), biological value (B.V.%) and percentage satisfaction of indispensable amino acids upon consuming 150g of the product (P.S./150g%). The (GDR value) grams consumed to cover the daily requirements of indispensable amino acids for adult man were lower. Thermophilic bacteria were not detectable and TBC were within the Egyptian standard specification (E.O.S., 1990). The consumption of 150g (one jar) of canned crayfish product covered the major minerals by about P (80–95%), Ca (72–92%), Mg (47–75%), Na (31–36%) and K (19–24%). Thus, canned Crayfish products under investigation had a high nutritional quality and acceptability as arranged in the following order, canned Crayfish with tomato sauce in green peas (CCP) was the best treatment, followed by canned Crayfish with tomato sauce in green beans (CCB) and canned Crayfish with tomato sauce (control) (CCC).

Current issues in determining dietary protein and amino-acid requirements

Pregnancy and the first two years of life are periods of rapid growth and yet the knowledge of requirements for protein and dietary indispensable amino acids is very limited. The development of carbon oxidation methods opens the way to studies that should fill these important gaps in knowledge.

No protein intake compensation for insufficient indispensable amino acid intake with a low-protein diet for 12days.

BackgroundProtein quality evaluation aims to determine the capacity of food sources and diets to meet protein and indispensable amino acid (IAA) requirements. This study determined whether nitrogen balance was affected and whether dietary IAA were adequately obtained from the ad libitum consumption of diets at three levels of protein from different primary sources for 12 days.MethodsTwo 12-day randomized crossover design trials were conducted in healthy subjects [n = 70/67 (M/F); age: 19-70 y; BMI: 18.2-38.7 kg/m2]. The relative dietary protein content was lower than [5% of energy (En%)], similar to (15En%), and higher than (30En%) customary diets. These diets had a limited variety of protein sources, containing wheat protein as a single protein source (5En%-protein diet) or 5En% from wheat protein with 10En% (15En%-protein diets) or 25En% (30En%-protein diets) added from whey with α-lactalbumin, soy or beef protein.ResultsThere was a dose-dependent increase in nitrogen excretion with increasing dietary protein content, irrespective of the protein sources (P = 0.001). Nitrogen balance was maintained on the 5En%-protein diet, and was positive on the 15En%- and 30En%-protein diets (P < 0.001) over 12 days. Protein intake from the 5En%-protein diet did not reach the amount necessary to meet the calculated minimal IAA requirements, but IAA were sufficiently obtained from the 15En%- and 30En%-protein diets. In the 15En%- and 30En%-protein conditions, a higher protein intake from the soy-containing diets than from the whey with α-lactalbumin or beef containing diets was needed to meet the minimal IAA requirements.ConclusionProtein intake did not compensate for an insufficient indispensable amino acid intake with a low-protein diet for 12 days.Trial registrationThese trials were registered at clinicaltrials.gov as NCT01320189 and NCT01646749.

Development of a semipurified test diet for determining amino acid requirements of Florida pompano Trachinotus carolinus reared under low-salinity conditions

Abstract Two trials were conducted to develop a semipurified test diet for determining indispensable amino acid (IAA) requirements for Florida pompano Trachinotus carolinus . The objective of the first trial was to evaluate casein and corn gluten meal as principal intact protein sources, and the ability of Florida pompano to utilize l -crystalline amino acids in the diet. Eight isonitrogenous (42% crude protein) and isoenergetic (22.0 kJ/kg) diets were formulated. A 2 × 4 factorial was employed to evaluate the two intact proteins, each with four amino acid profiles that mimicked the ratio of IAA in pompano whole body, pompano unfertilized eggs, menhaden fish meal, or unsupplemented negative control. Growth and efficiency were significantly better ( P The objective of the second trial was to re-evaluate the same IAA profiles in 46% crude protein and 22.0 kJ/kg casein-based diets to evaluate their performance relative to each other and to a practical type fish meal-based control diet. Growth and feed conversion were significantly better ( P P

Amino acid requirements in children and the elderly population

The factorial approach is used to measure the dietary indispensable amino acid (IAA) requirements in children, although recent measurements based on the indicator amino acid oxidation (IAAO) method have begun to generate more direct evidence. Difficulties with the factorial method are that it depends on accurate estimates of the maintenance protein requirement, as well as of protein deposition during growth. Also, a value for the efficiency of utilizing dietary protein for deposition has to be selected, based on published Nitrogen (N) balance studies. In the recent 2007 WHO/FAO/UNU report, the amino acid requirement pattern for infants was taken to be similar to the amino acid composition of breast milk. For pre-school and older children, the factorial method gave values for the scoring pattern of protein that were fairly close to the earlier 1985 WHO/FAO/UNU report for children, since growth progressively became a smaller component of the factorial calculation as age progressed. However, given that there are several assumptions in the derivation of factorial estimates, direct experimental measurements of the amino acid requirement are desirable. The IAAO method, as it is non-invasive, as made it possible to measure the IAA requirements in children. Over the last decade, some of the IAA requirements have been determined by using the IAAO method in healthy school age children; however, the data on IAA requirements in developing country populations are still being conducted. In the elderly, there are not enough data to make a separate recommendation for IAA requirements from that of adults.

Available versus digestible amino acids – new stable isotope methods

The nutritive value of food protein sources is dependent on the amino acid composition and the bioavailability of the nutritionally indispensable amino acids. Traditionally the methods developed to determine amino acid bioavailability have focused on intestinal absorption or digestibility, which is calculated as the percent of amino acid intake that does not appear in digesta or faeces. Traditional digestibility based methods do not always account for gut endogenous amino acid losses or absorbed amino acids which are unavailable due to the effect of heat processing and the presence of anti-nutritional factors, though methods have been developed to address these issues. Furthermore, digestibility based methods require the use of animal models, thus there is a need to develop in vivo methods that can be applied directly in human subjects to identify the proportion of dietary amino acids which is bioavailable, or metabolically available to the body for protein synthesis following digestion and absorption. The indicator amino acid oxidation (IAAO) method developed in our laboratory for humans has been systematically applied to determine almost all indispensable amino acid requirements in adult humans. Oxidation of the indicator amino acid is inversely proportional to whole body protein synthesis and responds rapidly to changes in the bioavailability of amino acids for metabolic processes. Using the IAAO concept, we developed a new in vivo method in growing pigs, pregnant sows and adult humans to identify the metabolic availability of amino acids in foods. The stable isotope based metabolic availability method is suitable for rapid and routine analysis in humans, and can be used to integrate amino acid requirement data with dietary amino acid availability of foods.

Effect of crude protein and fat content of diet on productive performance and egg quality traits of brown egg-laying hens with different initial body weight

A trial was conducted to study the influence of CP and fat content of the diet on performance and egg quality traits of brown egg-laying hens from 22 to 50 wk of age. The experiment was conducted as a completely randomized design with 8 treatments arranged factorially with 4 diets and 2 initial BW of the hens (1,592 vs. 1,860 g). Three of these diets differed in the CP content (16.5, 17.5, and 18.5%) and included 1.8% added fat. The fourth diet also had 18.5% CP but was supplemented with 3.6% fat instead of 1.8% fat. Each treatment was replicated 4 times, and the experimental unit consisted of 21 hens allocated into groups of 7 in 3 adjacent cages. All diets were isocaloric (2,750 kcal of AME/kg) and met the recommendations of brown egg-laying hens for digestible Arg, Ile, Lys, Met, Thr, Trp, TSAA, and Val. Productive performance and egg quality were recorded by replicate every 28 d. For the entire experimental period, diet did not affect any of the productive performance traits studied, but the heavier hens had higher ADFI (120.6 vs. 113.9 g; P < 0.001), egg production (92.5 vs. 89.8%; P < 0.01), and egg weight (64.9 vs. 62.4 g; P < 0.001) than the lighter hens. Initial BW did not affect feed conversion per kilogram of eggs or hen mortality, but BW gain was higher (289 vs. 233 g; P < 0.01) and feed conversion ratio per dozen of eggs was better (1.52 vs. 1.57; P < 0.01) for the lighter than for the heavier hens. None of the egg quality variables studied was affected by dietary treatment or initial BW of the hens. It is concluded that brown egg-laying hens, irrespective of their initial BW, do not need more than 16.5% CP to maximize egg production, provided that the diet meets the requirements for key indispensable amino acids. Heavier hens produce more eggs that are larger than lighter hens but feed efficiency per kilogram of eggs is not affected.

Methods to assess amino acid requirements in humans

There are now different stable isotopic methods to measure minimum daily human indispensable amino acid (IAA) requirements. There has been debate on the appropriateness of statistical methods used to define the nature of change in the response. Current isotopic methods measure daily amino acid oxidation and balance of the IAA under test, or of a selected indicator amino acid, to graded intakes of the test IAA. A key concern is how response curves of oxidation/balance are analyzed to find the inflection point (breakpoint) at which the intake requirement is identified. Evaluating the pattern of the response to identify a breakpoint by a two-phase regression appears best. The indicator amino acid oxidation method has also been shortened and developed into a noninvasive protocol suitable for different populations and age groups. The indicator amino acid oxidation and balance method might be considered the best approach currently available, but it is challenging. The short-term indicator oxidation method is noninvasive and nondemanding. IAA requirements, based on these methods, have implications for the quality of protein in the dietary intake of populations. Methods that assess the IAA requirements to support optimal body function also need to be developed.

Egg and whole-body amino acid profile of African bonytongue (Heterotis niloticus) with an estimation of their dietary indispensable amino acids requirements

African bonytongue, Heterotis niloticus, is a river fish from the Central and West Africa basin. The species presents a great potential for fish farming and has been increasingly raised in Central and South Cameroon. The total amino acid and proximate composition of the whole body of egg, larva, juvenile, immature, and adult Heterotis were determined. Ash, moisture, whole-body protein, and lipid contents were significantly affected by size (P < 0.05). On the other hand, the amino acid composition of the whole-body tissue, when expressed as a percentage of dietary protein, was not significantly different among ontogenetic stages (ranging from 0.2 to 400 g mean body mass). The amino acid composition of the eggs was quite different to the one of whole-body tissue with lower levels of methionine, proline, and glycine, and higher levels of arginine, histidine, isoleucine, leucine, threonine, valine, serine, and alanine. The A/E ratios of adult Heterotis muscle tissue are similar to those obtained for other fish species, except for histidine and tryptophan. Based on whole-body or muscle tissue indispensable amino acids (IAA) to A/E ratios, the IAA requirement profiles for Heterotis (from larva to adult) were estimated and are similar to those of other omnivorous fish species, except for tryptophan and histidine.

Effects of protein-, peptide- and free amino acid-based diets in fish nutrition

In the present review, we summarize data related to the utilization of purified diets formulated with the purpose of determining the amino acid requirements in fish independent of the ontogenetic stage and the morphological characteristics of the digestive tract. Expanding present knowledge on the formulation of protein, free amino acid (FAA) and synthetic dipeptide-based diets can provide possible insights that might lead to a better understanding of the mechanism of amino acid utilization in the growth of fish. Differences exist in the utilization of protein, dipeptides or free amino acids for growth between stomach-possessing and stomachless fish with respect to their response to manipulating the proportion of protein and dipeptides in the formulas. Free amino acid-based diets are uniformly inferior. The effects of diet manipulation on indispensable FAA concentrations in the body (muscle) are not simply the result of deamination or the protein synthesis/degradation ratio. The hydroxyproline/proline ratio was confirmed to be of value in quantifying muscle collagen degradation/synthesis and can perhaps be used to quantify the amino acid requirement necessary to maximize the utilization (deposition) of dietary amino acids. In summary, indispensable amino acid requirements for maximum growth in fish can be addressed using diets formulated from protein/peptide/FAA sources.

Maintenance and growth requirements for nitrogen, lysine and methionine and their utilisation efficiencies in juvenile black tiger shrimp,Penaeus monodon, using a factorial approach

We used a factorial approach to distinguish maintenance from growth requirements for protein, lysine and methionine in the black tiger shrimp, Penaeus monodon. Juvenile P. monodon (initial weight 2.4 g) were fed during 6 weeks one of ten semi-purified diets based on casein and purified amino acids (AA) as N source. The diets contained four levels of crude protein (CP, from 5 to 54 % DM diet) with two levels (% CP) of lysine or methionine (normal or 30 % deficient). Requirements were determined using linear and non-linear regression models. We could thus obtain the first ever data on maintenance (N equilibrium) requirements for CP and AA in P. monodon. CP requirements for maintenance (4.5 g/kg body weight (BW) per d) represented approximately 19 % of the CP requirement for maximal N gain (23.9 g/kg BW per d). The marginal efficiency of utilisation reached a maximum of 38 % for N, 0.77 for lysine and 1.62 for methionine using N gain as response. Lysine requirements were 0.20 g/kg BW per d for N maintenance and 1.40 g/kg BW per d for maximal N gain. Methionine requirements were 0.11 g/kg BW per d for N maintenance and 0.70 g/kg BW per d for maximal N gain. The lysine (5.8 %) and methionine (2.9 %) requirements for maximal N gain, expressed as percentage of protein requirement, agree with literature data using a dose-response technique with smaller P. monodon. The observed interaction between dietary CP and methionine for N gain demonstrates that requirements for indispensable AA (expressed as % CP) cannot be evaluated separately from CP requirements.