Determination Of Amino Acid Requirements Research Articles

A Comparison of two Empirical Methods of determining Amino Acid Requirements

The amino acid requirements of growing poultry may be determined by two empirical procedures, one involving graded supplementation of the test amino acid to a deficient basal diet, and the other in...

Studies on methods for the determination of amino acid requirements for metabolic balance based on the oxidation rate of 14C labeled lysine to 14CO2

Male experimental rats (100 gm liveweight) were distributed into 10 groups of 8 animals each and received balanced diets, with the exception of lysine which was added to the diets in graded amounts in such a way that the lysine content of the diets ranged from 2.44 to 5.92 gm/16 gm N. After a feeding period of 7 days the animals received 3H- and 14C lysine injected intraperitoneally, 4 animals of each group were investigated for the total CO2 excretion and 14CO2 excretion during the first 2 hrs after the injection and for the urinary excretion of radioactivity (48 hours). The remaining animals in each group were used for determining the plasma amino acids and for establishing the specific radioactivity of free lysine in the liver and muscles after an 1-hour incorporation period. Total CO2 excretion was not found to be influenced by the lysine contents while the level of excretion of 14C activity through CO2 and that of specific 14C activity of CO2 increased with increasing lysine concentrations. This produced a broken curve pattern, showing an increased release of 14CO2 (under maintenance conditions) if the diet contained 4 gm lysine/16 gm N and more. Investigations for the specific 14C activity of free lysine in the liver, the main site of lysine oxidation, showed that the increase in 14CO2 release was due to an enhanced rate of lysine catabolism and was not brought about by changes in the pool volume or in specific radioactivity. The levels of urinary 14C excretion were not found to be related to the lysine content of the diets, whereas the curve pattern of 3H excretion observed 5 to 8 hrs after injection was similar to that of 14CO2 excretion. The lysine content of blood plasma and the content of free lysine in the liver increased continuously with increasing levels of dietary lysine. The methodological studies made in the present paper showed that in scientific research a determination of amino acid requirements on the basis of CO2 oxidation data may be a very exact and sensitive method. It will also yield values for maintenance requirements.

The amino acid requirements of the growing chick. I. Determination of amino acid requirements.

Synopsis The amino acid requirements of the growing chick have been determined using a diet based on soybean meal and maize meal. The diet contained 18% protein (N% x 6.25, dry matter basis) made up to 14% contributed by conventional ingredients and 4% protein equivalent in the form of amino acids. Starting with a diet formulated to meet the reference levels recommended by Dean and Scott (1965) a programme of experiments was carried out to improve this amino acid balance. The results indicated that the growing chick requires not more than 0.53% threonine, 0.61% glycine, 0.79% valine, 0.62% isoleucine, 1.34% leucine, 0.75% phenylalanine (or 1.3% phenylalanine plus tyrosine), 0.85 % lysine, 0.4% histidine, 0.86% arginine, 0.17% tryptophan and 0.39% methionine (or 0.79% methionine plus cystine).

The determination of the methionine requirement of laying pullets by a diet dilution technique

Synopsis A method for the determination of amino acid requirements of laying hens is described. This involves the dilution of a high protein “ summit” diet with an isocaloric nitrogen‐free mixture. By ensuring that the amino acid to be assayed is first‐limiting in the summit diet, the response to dilution can be interpreted as a response to a single amino acid. The method is applied to the determination of methionine requirement and it is shown that the response to methionine obtained is virtually independent of the protein level of the diet and is not influenced by direct effects of the dilution mixture. From the results of the present and other published experiments, the “ available “ methionine required for maximum egg yield of pullets in the early stages of lay is estimated to be 275 mg per bird per day.

Amino Acid Requirements of Grain Beetles

Development of a diet purified with respect to amino acids has led to the determination of amino acid requirements of several grain beetles. The confused flour beetle, Tribolium confusum (Duval), required (in per cent of diet) arginine, 0.5; histidine, 0.2; isoleucine, 0.5; leucine, 0.8; lysine, 0.56; methionine, 0.3 (0.15 with excess cystine); phenylalanine, 0.7 (0.4 with excess tyrosine); threonine, 0.4; tryptophan, 0.1; and valine 0.6. The red flour beetle, Tribolium castaneum (Herbst), required (in per cent) arginine, 0.4; histidine, 0.2; isoleucine, 0.3; and leucine, 0.7. The saw-toothed grain beetle, Oryzaephilus surinamensis (L.), required (in per cent) arginine, 0.3; histidine, 0.2; isoleucine, 0.3; and leucine 0.6. Other amino acid requirements for the latter 2 insects were not determined. Requirements of these grain insects are compared with those of other organisms. The confused flour beetle was tested as an assay organism for amino acid content of protein but showed little promise.

Nutrition of the pale western cutworm, Agrotis orthogonia Morr. (Lepidoptera, Noctuidae)—IV : Amino acid requirements determined with glucose-U-C 14

An indirect method using glucose-U-C 14 to determine amino acid requirements was applied to fifth instar larvae of the pale western cutworm, Agrotis orthogonia Morr. C 14O 2 was produced after glucose-U-C 14 was injected, indicating that the substrate was metabolized. The amino acids, alanine, aspartic acid, glutamic acid, proline, serine, and cysteic acid, isolated from the larvae contained relatively large quantities of radioactivity and were classed as nutritionally non-essential. Phenylalanine, arginine, lysine, histidine, leucine, isoleucine, and cystine contained little radioactivity and were classed as nutritionally essential. Methionine is probably essential also. The requirement for threonine remains in doubt. Tyrosine was not synthesized appreciably from glucose-U-C 14 but was readily formed from phenylalanine.

A Criticism of the Carcass Analysis Procedure for the Determination of Amino Acid Requirements

AbstractThe carcass analysis procedure is examined as a method for the determination of amino acid requirements. Using a simple reaction sequence to illustrate the fate of an amino acid in the body, enzyme kinetics are applied to demonstrate the impossibility of estimating the requirement of one compound in relation to another from knowledge of only the concentrations of the two compounds in the organism. The further complications arising from (a) the known individual variations in the concentrations of enzymes in the body, (b) the utilization by the organism of certain essential amino acids for purposes other than protein synthesis, (c) the partial ability of the organism to synthesize some essential amino acids, (d) the different rates of breakdown and excretion of the amino acids and (e) the fact that the body consists not of one but of a large number of different proteins with varying metabolic stability are briefly discussed. Some experimental data are cited which indicate that the carcass analysis procedure can give requirement values that are greatly erroneous. The criticism is presented with the hope that it will stimulate further theoretical and experimental studies in order to define the limitations and possibilities of the method.

Studies on a Short-Term Procedure for Determining Amino Acid Requirements of Laying Hens

MACHLIN (1954) reported that a reduction of dietary protein or tryptophan eleven days after administration of methionine-S35 to laying hens resulted in a relative increase in sulfur35 deposition in the egg albumen. This increase in deposition of sulfur35 due to an amino acid deficiency suggested a possible procedure for estimating dietary amino acid requirements of the laying hen. Fisher and Johnson (1956) reported the development of a synthetic diet containing free amino acids instead of protein that maintained egg production for a 30-day experimental period. Since the cost of conducting research with synthetic diets of this type limits the duration of the experimental periods, an assay procedure whereby amino acid deficiencies could be detected in a short period of time would be valuable for determining dietary amino acid requirements.The following studies using a lysine deficient laying diet were designed to ascertain if the results obtained by the procedure described …