Estimation Of Amino Acid Requirements Research Articles

Relative Concentrations of Amino Acids in the Exoskeleton of Male and Female Neopetrolisthes Maculatus

Amino acid levels in the exoskeleton of the heterosexual samples of Neopetrolisthes maculatus were evaluated. Twenty parameters were reported on; 13 of these values were greater in the female than the male (i.e. 13/20 or 65.0%). Values in female > male were observed in Val, Thr, Lys, Met, Phe, Trp, Gly, Ala, Asp, Arg, Cys, total amino acids and protein. The variations between the male and female amino acid values were low having coefficient of variation percent range of 0.0579-16.9. The amino acid levels were significantly different between the heterosexuals at r=0.01. Limiting amino acids on the various scoring standards were egg (Cys=0.3172 and 0.3511), provisional essential amino acid scoring pattern (Lys = 0.4145 and 0.4746), preschool child requirements (Lys =0.3930 and 0.4501) and all the three scores were significantly different at r=0.01. The EAAI1 (compared to soybean) were 1.18 (male) and 1.16 (female), EAAI2 (compared to egg) were 88.5 (male) and 88.3 (female); their corresponding BV were 84.7 and 84.5. P-PER1 range was 1.86 (male) - 1.24 (female) and P-PER2 range was 2.02 (male) - 1.41 (female). Total EAA was 37.7g/100g protein (male) and 37.0g/100g protein (female). In the estimates of amino acid requirements of school boys at ages 10-12years (mg/kg/day), male exoskeleton would provide more than the requirement in Phe + Tyr (186%), Trp (25.8%) and Val (48.1%) whereas in female the following were higher than the standards: Phe + Tyr (218%), Thr (8.86%), Trp (35.0%), Val (61.6%) and TEAAs (4.01%)

Amino Acid Composition of Kilishi - Nigerian (Beef Jerky) Meat

The article reports the amino acid composition of Nigerian beef jerky meat called Kilishi. Kilishi is consumed dry, hence determination was on dry weight basis. Sample was purchased in Ado-Ekiti, Nigeria. Amino acid values were highest for non-essential amino acid in Glu (14.3 g100g-1) whereas from essential amino acid it was Lys (8.69 g100g-1). Other high value amino acids were (in g100g-1): Asp (8.85), Leu (7.68), Arg (6.02), Ile (4.08), Trp (1.02), Cys (1.18) and His (2.40). P-PER1,2,3values were superior at values of 2.52 – 2.70. EAAI1(soybean standard) was 1.23 and EAAI2(egg standard) was 94.5 with corresponding BV of 91.3. Lys/Trp was very high at 8.55 and Met/Trp was 2.38. Values of TNEAA was 52.1 g100g-1(57.7%) and TEAA was 38.2 g100g-1(42.3%). In the egg score comparison Ser (0.461) was the limiting amino acid (LAA) with protein corrected digestibility value of 0.338; in provisional EAA scoring pattern, LAA was Val (0.882) and corrected version was 0.742; in pre-school children requirement, LAA was Trp (0.927) and corrected value of 0.780. Variation percentage values between the scores/corrected scores were virtually 12.2% per parameter compared. Correlation values between each score standard/corrected score values were significantly different at r=0.01with values of 0.9997 – 0.99999. Estimates of amino acid requirements at ages 10 – 12 years (mg kg-1day-1) showed kilishi to be better than the standards at 74.9% - 453%. Results showed that kiishi is protein-condensed.

Simulated amino acid requirements of growing pigs differ between current factorial methods

Significant differences in the estimation of amino acid requirements exist between the available factorial methods. This study aimed to compare current factorial models used to estimate the individual and population standardised ileal digestible (SID) lysine (Lys) requirements of growing pigs during a 26-day feeding phase. Individual daily feed intake and BW data from 40 high-performance pigs (25-kg initial BW) were smoothed by linear regression. Body weight gain was constant (regression slope not different from 0) for all the pigs. The CV of the SID Lys requirements ranged from 22% at the beginning of the trial to 8% at the end. The population Brazilian tables (BT-2017) and National Research Council (NRC-2012) SID Lys requirements for the average pig were 16% higher than the average requirement estimated by the individual precision-feeding model (IPF), but similar to the estimated for the population assuming that population requirements are those of the 80th-percentile pig of the population (IPF-80). Meaning that, the IPF-80, BT-2017, and NRC-2012 models would yield similar recommendations when pigs are group-fed in conventional multi-phase systems. Additionally, the IPF-80 estimates are independent of the phase length, whereas the BT-2017 and NRC-2012 models use average population values in the middle of the feeding phase for the calculations and therefore, conventional requirement estimations decrease as the length of the feeding phase increases. In conclusion, the BT-2017 and NRC-2012 methods were calibrated for maximum population responses, which explains why these methods yield higher values than those estimated for the average pig by the IPF model. This study shows the limitations of conventional factorial methods to estimate amino acid requirements for precision-feeding systems.

Improving the estimation of amino acid requirements to maximize nitrogen retention in precision feeding for growing-finishing pigs

Precision feeding requires a mathematical model to estimate standardized ileal digestible (SID) lysine (Lys) requirements (SIDLysR) in real time. However, this type of model requires constant calibration updates. The objective of this study was to review the calibration of the model used to estimate the real-time Lys requirements of individual growing-finishing pigs. A digestibility trial (n = 10) was conducted to evaluate amino acids digestibility during the growing and finishing phases. Additionally, 120 pigs were used in two 28-day growth experiments conducted as completely randomized design with growing (25 ± 2.1 kg BW, n = 60; 10 pigs per treatment) or finishing barrows (68.1 ± 6 kg BW, n = 60; 10 pigs per treatment). In each experiment, the pigs were divided into six equal treatment groups and fed 60%, 70%, 80%, 90%, 100% or 110% of their estimated individual SIDLysR. The Lys requirement of each pig was estimated daily using a real-time model. Body composition was measured with dual-energy X-ray densitometry on day 1 and 28 of the experiments. Average daily feed intake increased quadratically (P < 0.05) during both growth phases. Maximum average daily gain (ADG) (0.98 kg) and maximum protein deposition (PD; 170 g/day) were observed in growing pigs fed 100% of the estimated SIDLysR (P < 0.001). During the growing period, PD in BW gain (17% to 19%) and N efficiency (52% to 65%) increased linearly (P < 0.01) with increasing inclusion rates of SID Lys. Finishing pigs had maximum ADG (1.2 kg/day) when they were fed 100% of the requirements. However, the amount of protein in BW gain (13% to 16%) and N efficiency (40% to 55%) increased linearly (P < 0.01) with increasing inclusion rates of SID Lys. In conclusion, the model proposed for precision feeding is correctly calibrated to predict SIDLysR that maximize PD and ADG of average pigs from 25 to 50 kg BW. Still, there is an opportunity to improve the estimation of SIDLysR and N retention in individual pigs by better representing the individual proportion of protein in BW gain and the factors controlling the efficiency of Lys utilization in individual pigs.

Precision livestock farming: real-time estimation of daily protein deposition in growing–finishing pigs

Precision feeding using real-time models to estimate daily tailored diets can potentially increase nutrient utilization efficiency. However, to improve the estimation of amino acid requirements for growing–finishing pigs, it is necessary to accurately estimate the real-time body protein (BP) mass. The aim of this study was to predict individual BP over time in order to obtain individual daily protein content of the gain (i.e., protein deposition/daily gain, PD/DG) to be integrated into a real-time model used for precision feeding. Two databases were used in this study: one for the development of the equations for the model and the other for model evaluation. For the equations, data from 79 barrows (25 to 144 kg BW) were used to estimate the parameters for a Gompertz function and a mixed linear-quadratic regression. Individual BP predictions obtained by dual X-ray absorptiometry were regressed as a function of BW. Individual pig BP estimates were obtained by linear-quadratic regression using the MIXED procedure of SAS, considering pig measurements repeated in time. Individual Gompertz curves were obtained using the NLMIXED procedure of SAS. Both procedures generate an average or a general model, which was assessed for accuracy with the database used to generate the equations. Coefficients of concordance and determination were both 0.99, and the RMSE was 0.21 kg for the linear-quadratic regression. The Gompertz curve coefficients of concordance and determination were both 0.99, and the RMSE was 0.36 kg. In sequence, the linear-quadratic regression and Gompertz curve were evaluated in an independent data set (488 observations; 21 to 126 kg BW). The linear-quadratic regression to predict BP mass was accurate (mean absolute percentage error (MAPE) = 2.5%; bias = 0.03); the Gompertz model performed worse (MAPE = 3.9%; bias = 0.04) than the linear-quadratic regression. When using the derivative of these equations to predict PD/DG, the linear-quadratic regression was more accurate (MAPE = 4.8%, bias = 0.17%) compared to the Gompertz (MAPE = 10.6%, bias = −0.99%) mainly due to the linear decrease in PD/DG in the observed data. Further analysis using individual pig data showed that the goodness of fit of PD/DG curve depends on the individual shape of the growth curve, with either the Gompertz or the linear-quadratic regression being more accurate for specific individuals. Therefore, both approaches are provided to allow end users to select the model that best fits their needs. The proposed update of the empirical component of the original model, using either linear-quadratic regression or the Gompertz function, is able to predict BP in real-time with good accuracy.

Effect of digestible methionine + cystine concentration on performance, egg quality and blood metabolites in laying hens

The estimation of sulphur amino acid requirement is a vital key to providing appropriate nutrition in poultry. The estimation of amino acid requirement depends on what production parameter is taken into consideration for optimisation.A complete randomised block design was performed with 5 treatments and 6 replicates of 8 Hy-line layers (W-36) each from 32 to 44 weeks of age. The blocks were made to have a replicate of each treatment. The dietary treatments were consisted of 5 concentrations of digestible sulphur amino acid (DSAA) at 5.1, 5.6, 6.1, 6.6 and 7.1 (g/kg).Egg production, egg mass, egg weight and feed conversion ratio (FCR) were significantly affected by an increase in DSAA intake. However, feed intake, egg component yield, Haugh unit, specific gravity, eggshell thickness, egg protein and dry matter (DM) were not altered by DSAA intake.A significant increment in plasma high-density lipoprotein was concomitant with a reduction in low-density lipoprotein when DSAA intake was increased. However, triglyceride, cholesterol, uric acid and total protein in plasma were not affected by DSAA intake.The DSAA requirements estimated by the linear broken-line model to optimise egg production, egg mass, egg weight and FCR were 678, 673, 641 and 656 mg/bird.d in the whole experimental period, respectively.The DSAA requirement estimated by the quadratic broken-line model to optimise egg production, egg mass, egg weight and FCR were 4.71%, 7.87%, 8.73% and 7.62% higher than those estimated by linear broken-line fit model in the whole experimental period, respectively.

Dietary phenylalanine requirement of adult Labrador Retrievers using the direct oxidation approach

Historically, the determination of amino acid (AA) requirements in dogs have been done in growing dogs and have been invasive in nature, requiring long periods of confinement and exposure to diets deficient in AA, which result in a reduction in the health and well being of dogs during the study period. Therefore, we were interested in examining whether carbon oxidation methods, with short periods of exposure to diets deficient in a single AA, could be successfully applied to determine AA requirements in dogs. Four adult Labrador Retrievers consumed 7 levels of phenylalanine (Phe), and excess tyrosine (Tyr) in random order and in combination with kibble that was formulated to be deficient in Phe and adequate in dietary energy (3730 kcal/kg as fed) and fed at ~13.5 g kg−1 BW d−1. Dogs were fed test diets for two days prior to conducting the tracer studies. The Phe requirement was determined by applying a 2‐phase linear regression crossover model to tracer oxidation (F13CO2). The mean Phe requirement was 3.27 g/kg diet (upper 95% CI= 4.96 g/kg diet) on a dry matter basis. The current NRC estimate of the adequate intake for Phe is 4.50 g/kg diet and based on growth and nitrogen balance in growing dogs. This magnitude of difference is similar to that seen when estimates of AA requirements in humans using nitrogen balance vs. carbon oxidation methods are compared.

Potential for protein deposition and threonine requirement of modern genotype barrows fed graded levels of protein with threonine as the limiting amino acid.

The study was conducted to estimate the actual genetic potential for daily protein deposition of growing barrows [genotype: Piétrain x (Duroc x Landrace)]. Twenty-four pigs with an average initial body weight (BW) of 43.7 +/- 0.7 kg were used in a N-balance study. Semi-purified diets with graded levels of crude protein (45.8, 94.2, 148.0, 198.9, 255.5 and 300.2 g/kg DM) were used, based on a constant mixture of wheat, soya bean protein concentrate and potato protein concentrate as protein sources. The amino acid pattern of the diets was according to the ideal amino acid ratio for growing pigs (Wang and Fuller, 1989), with the exception of threonine (adjusted as limiting amino acid). N-balance data were used to estimate daily N-maintenance requirement (NMR = 446 mg N/BW0.67 kg/day) by regression method and the theoretical maximum of daily N-retention (PDmaxT = 3115 mg N/BW0.67 kg/day) based on N-utilization model of Gebhardt (1966) using program Mathematica 3.0. The results indicate that PDmaxT of pigs under study is much higher than results from earlier studies with older genotypes. In summary, pigs of modern genotype have a very high genetic potential for daily protein deposition and these actual data are important basic informations for estimation of amino acid requirement within the model used. Threonine requirement data depending on threonine efficiency and protein deposition (8.96, 10.45 and 12.22 g/day for 130, 145 and 160 g daily protein deposition; 50 kg body weight) are discussed.

Branched-Chain Amino Acid Requirements in School-Aged Children Determined by Indicator Amino Acid Oxidation (IAAO)

The current WHO/FAO/UNU recommendations for BCAA requirements in school-aged children are based on nitrogen balance studies that have tended to produce lower estimates of amino acid requirements that those determined using stable isotope methodologies. The new dietary reference intake (DRI) recommendations for total BCAA requirements in children were determined using a factorial approach that included adult BCAA requirements plus the additional needs for growth. The purpose of this study was to determine directly total BCAA requirements in school children aged 6-10 y using indicator amino acid oxidation (IAAO). Five children (8.5 +/- 1.2 y) were assigned randomly to receive 7 graded intakes of total BCAA. Individual BCAA in the test diet were provided in the same proportions as those present in egg protein to minimize the potential interactive effects of individual BCAA on assessment of requirement. Total BCAA requirement was determined by measuring the oxidation of L-[1-13C] phenylalanine to 13CO2 [F13CO2 in micromol/(kg x h)], after a primed, continuous infusion of the labeled tracer and using a two-phase linear crossover regression analysis. The mean requirement and the population-safe intake level (upper limit of the 95% CI) of the total BCAA in healthy school aged children were 147 and 192 mg/(kg x d), respectively. The estimated mean requirements of the total BCAA as determined by IAAO is approximately 48% higher than the current DRI recommendations, suggesting that these recommendations may be too low to meet the needs of school-aged children.

Accuracy of Omnipro® II Estimations for Amino Acid Requirements of Broilers

Estimation of amino acid requirements is a complex problem where many factors such as experimental conditions, genetic strain, gender, growth rate, protein quality and level of other dietary nutrients may interfere with the response. Due to the difficulties of using empirical research to resolve these problems, several mathematical growth models have been developed which could be useful for this purpose. Among the models proposed, the OmniPro II growth model was chosen to evaluate its accuracy to estimate protein ® and amino acid requirements for broilers under a commercial feeding program. Diets formulated based on levels of protein and amino acids estimated by OmniPro II were compared with diets based on NRC (1994) ® recommendations. Significant differences between sexes were observed for all variables evaluated. Broilers fed diets formulated with 100% of OmniPro II estimations had BW that was similar to those fed diets based ® on NRC or 110% OmniPro, and were significantly heavier than those fed the 90% OmniPro diets. The feed conversion of male broilers fed diets based on OmniPro recommendations was significantly better than that of chicks fed diets based on NRC recommendations. Females fed with diets according to OmniPro or NRC had the highest dressing percentage, and differed only from those fed the 90% OmniPro diets. These data suggest that nutrient estimations generated by the OmniPro II support performance equal to or better than ®

Kinetics of L-[1-(13)C]leucine when ingested with free amino acids, unlabeled or intrinsically labeled casein.

In two groups of five adults, each adapted to two different dietary regimens for 6 days, the metabolic fate of dietary [1-(13)C]leucine was examined when ingested either together with a mixture of free amino acids simulating casein (extrinsically labeled; condition A), along with the intact casein (extrinsically labeled; condition B), or bound to casein (intrinsically labeled; condition C). Fed state leucine oxidation (Ox), nonoxidative leucine disposal (NOLD), protein breakdown, and splanchnic uptake have been compared using an 8-h oral [1-(13)C]leucine and intravenous [(2)H(3)]leucine tracer protocol while giving eight equal hourly mixed meals. Lower leucine Ox, increased NOLD, and net protein synthesis were found with condition C compared with condition A (19.3 vs. 24.9; 77 vs. 55.8; 18.9 vs. 12.3 micromol. kg(-1). 30 min(-1); P < 0.05). Ox and NOLD did not differ between conditions B and C. Splanchnic leucine uptake calculated from [1-(13)C]- and [(2)H(3)]leucine plasma enrichments was between 24 and 35%. These findings indicate that the form in which leucine is consumed affects its immediate metabolic fate and retention by the body; the implications of these findings for the tracer balance technique and estimation of amino acid requirements are discussed.

Phenylalanine requirements determined by using L-[1-14C]phenylalanine in neonatal piglets receiving total parenteral nutrition supplemented with tyrosine

The definition of amino acid requirements for neonates receiving total parenteral nutrition (TPN) is critical for the further improvement of this nutritional regimen. In the present study we investigated the kinetics and requirements of phenylalanine and tyrosine in neonatal piglets receiving TPN. Twenty-four 3-d-old male Yorkshire piglets were fitted with external jugular and femoral catheters and maintained on identical TPN formulations for 5 d. Total amino acid, phenylalanine, tyrosine, and energy intakes were 15, 0.61, and 0.51 g. kg-1 . d-1 and 1.1 MJ . kg-1 . d-1, respectively. On day 5, piglets (three per level) were randomly assigned to receive one of eight phenylalanine intakes: 0.2. 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, or 1.2 g. kg-1 . d-1. On day 6, phenylalanine kinetics were measured during a 4-h primed, continuous infusion of L-[1-14C]phenylalanine. Plasma phenylalanine and phenylalanine oxidation were statistically similar for the three lowest phenylalanine intakes and increased thereafter. Crossover regression analysis yielded estimates for the mean requirement and safe phenylalanine intake of 0.45 and 0.48 g . kg-1 . d-1, respectively (equivalent to 30 and 32 mg/g amino acids, respectively), in the presence of excess tyrosine. An inability of piglets to maintain a linear oxidative response at phenylalanine intakes > 0.8 g . kg-1 . d-1 (equivalent to 53 mg/g amino acids) was found. These data represent the first direct estimates of phenylalanine requirements in neonates receiving TPN and demonstrate the use of oxidation techniques for the estimation of amino acid requirements during parenteral nutrition.

Tyrosine kinetics and requirements during total parenteral nutrition in the neonatal piglet: the effect of glycyl-L-tyrosine supplementation.

Tyrosine may be a conditionally indispensable amino acid in the neonate; however, the provision of aromatic amino acids to neonates receiving total parenteral nutrition (TPN) is complicated by the poor solubility of crystalline tyrosine. In the present study, we investigated tyrosine kinetics and requirements during TPN, when tyrosine was supplied as the soluble dipeptide, glycyl-L-tyrosine in a neonatal piglet model. Fifteen 3-d-old male Yorkshire piglets were fitted with external jugular and femoral catheters and randomized to one of five tyrosine intakes: 0.11, 0.31, 0.41, 0.51 and 0.71 g.kg-1.d-1. Total parenteral amino acid and energy intakes were 15.0 g.kg-1.d-1 and 1.1 MJ.kg-1.d-1, respectively. Piglets were maintained on TPN for 6 d, with nitrogen balance measured over the final 3 d of the study. On the final study day, tyrosine kinetics were measured during a 4-h primed-constant infusion of L-[l14C]tyrosine. Nitrogen retention was 67% at the lowest tyrosine intake and increased significantly (p < 0.05) at intakes of 0.31 g.kg-1.d-1 and above (84, 86, 87, and 88% for intakes of 0.31, 0.41, 0.51, and 0.71 g.kg-1.d-1, respectively). Plasma tyrosine concentrations and tyrosine oxidation (expressed as either a percentage of the dose oxidized or when corrected for flux) were low and similar at the two lowest intakes, but increased significantly at the higher intakes. Two-phase regression analysis of the data (plasma tyrosine, tyrosine oxidation) yielded estimates of a mean tyrosine requirement of 0.31 and 0.35, respectively, with estimated safe intakes (upper 95% confidence limit) of 0.44 and 0.42 g.kg-1.d-1. The present work also indicates that oxidation techniques may be suitable for the estimation of amino acid requirements during TPN in the neonate.

Protein nutrition of gestating sows.

Dietary amino acid requirements of gestating sows vary depending on genetic strain, energy intake, body weight, and other factors. Estimation of amino acid requirements for gestating sows in a defined situation should be directed toward achieving a high rate of protein accretion and a modest rate of fat accretion. More information is needed to set target accretion rates precisely. A simple mathematical model was developed with the limited objectives of 1) aiding in understanding the interactions among energy intake, amino acid intake, protein accretion potential, and body weight in affecting the amount of body protein and fat accreted by pregnant sows and 2) providing general guidelines for feeding programs. Predictions from the model suggest that the daily lysine requirement varies markedly with variation in ME intake but that the requirement as a percentage of the diet is more stable as ME intake varies. At moderate ME intake, the lysine requirement seems greater during late gestation than earlier. The lysine requirement of heavy sows is less than that of light gilts at a similar ME intake, and this offers opportunity for modest cost savings in pork production. A compromise is necessary between the goals of a high rate of protein accretion and a modest rate of fat accretion. It seems that a sow's potential protein accretion rate is rarely limiting.

Amino acid losses in ileostomy fluid on a protein-free diet

The contribution of losses via the gastrointestinal tract to maintenance amino acid requirements was assessed by collecting the ileostomy fluid of volunteers given a protein-free diet for 5 d. The subjects were eight adult men and women with terminal ileum ileostomies after ulcerative colitis. Four consecutive 24-h collections of both digesta and urine were made. On the last 2 d an antibiotic was given that suppressed microbial activity in the digesta and slightly reduced ileostomy outflow. Mean daily amino acid excretion in ileostomy fluid ranged from 32 mg/d for methionine to approximately 330 mg/d for aspartate and glutamate. These losses were compared with current international estimates of amino acid requirements. For most essential amino acids gastrointestinal losses accounted for 14-33% of daily maintenance requirements but for threonine the contribution was 61%.

Quantities of amino acids ingested by human milk-fed infants

The purpose of this investigation was to provide quantitative data on amino acids ingested by human milk-fed infants. Ten term infants fed human milk ad libitum were studied at 2, 4, and 8 weeks of age. Measurements of milk volume and amino acid analyses of milk samples were performed. Both total amino acid and nitrogen intakes (mumole/kg/day) declined by approximately 34% during the study (P less than 0.001) to 0.05), primarily because of a 20% decline in respective concentrations in human milk (P less than 0.001). Consequently, markedly different amino acid intakes were observed at 2 and 8 weeks. Quantities of amino acids consumed by nearly every infant exceeded estimated Food and Agriculture Organization/World Health Organization requirements at 2 weeks. However, mean intakes for seven of nine essential amino acids studied (phenylalanine, tyrosine, methionine, threonine, valine, leucine, and lysine) were less than recommended quantities at 8 weeks. These same relationships between observed and recommended intakes were also evident at 4 weeks, except for lysine and leucine. Mean intakes of histidine and isoleucine exceeded estimated requirements at all times. These data indicate that FAO/WHO estimates of amino acid requirements may be inflated for phenylalanine, tyrosine, methionine, threonine, valine, leucine, and lysine.

Studies on the Amino Acid and Protein Requirements of Laying Japanese Quail (Coturnix coturnix japonica)

Six experiments were conducted to define the amino acid and protein requirements of laying Japanese quail. In the initial experiments the diets contained 12% protein from a mixture of casein and soybean meal and were supplemented with essential amino acids and glutamic acid to promote optimum egg production. Later studies were conducted with corn-soybean meal diets. Results from varying the levels of essential amino acids led to. the following estimates of amino acid requirements (as percent of the diet): arginine, 1.13; histidine, .38; isoleucine, .81; leucine, 1.28; lysine, .86; methionine plus cystine, .68; phenylalanine plus tyrosine, 1.25; threonine, .67; tryptophan, .17; and valine, .83. These amino acid requirements are correlated with the amino acid composition of quail eggs (r = .74). The total protein requirement of laying Japanese quail was found to be slightly greater than 16% of the diet when quail were fed diets based on either casein and soybean meal alone or casein and soybean meal supplemented with essential amino acids and glutamic acid. Based on the consumption of from 18 to 19 g of this diet per day the daily protein requirement was 2.88 to 3.08 g. Quail fed a methionine supplemented corn-soybean meal diet consumed up to 22 g of feed per day resulting in an estimated protein requirement of 3.52 g per day.

Use of Free Plasma Amino Acid Levels for Estimating Amino Acid Requirements of the Growing Rat

The validity of using plasma amino acid levels for estimating amino acid requirements of the growing rat was investigated. A series of diets was prepared (equivalent to 10% protein, provided by whole egg and an amino acid mixture simulating egg proteins) having graded levels of the amino acid under test. These test diets were fed to groups of 10 male Wistar rats, 28 to 30 days old, for 3 days. The amino acid under test was determined in the plasma of individual rats by microbiological assay. The dose-response curve relating plasma level and dietary level of the test amino acid was drawn. The requirement was considered to be the dietary level at which the corresponding plasma level was equal to the normal fasting level. Requirements expressed as percentage of diet were estimated to be: lysine, 0.65; tryptophan, 0.13; threonine, 0.42; leucine, 0.82; isoleucine, 0.50; and histidine, 0.20. Estimates of amino acid requirements of the rat were in close agreement with average values obtained by other methods reported recently in the literature.