Abnormal concentrations of B vitamins and amino acids in plasma, bile, and liver of chicks with aflatoxicosis.

Graded levels of aflatoxin fed to broiler chickens for 3 weeks decreased the levels of most B vitamins in plasma, bile, and liver and decreased all free and hydrolyzed amino acids from peptides in plasma. The levels of thiamine, riboflavin, vitamin B6, pantothenic acid, and choline decreased by more than 60% in bile; vitamin B6, pantothenic acid, and choline decreased by more than 49% in plasma; thiamine, vitamin B6, pantothenic acid, choline, folate, and niacin decreased by more than 19% in liver; and only bile and plasma levels of folate increased (78 and 12%, respectively) with a dietary level of 5 microgram of aflatoxin per g of feed. Plasma levels of cystine and cysteine, methionine, threonine, serine, and aspartic acid decreased by more than 37%, whereas valine, lysine, leucine, histidine, hydroxyproline, and alanine decreased by more than 9% with 2.5 microgram of aflatoxin per g of feed. The data suggest that aflatoxin interferes with the metabolism of B vitamins and amino acids in chicks. However, these changes may be measuring the effects of aflatoxin-induced hepatic necrosis.     

Metabolism of L-(U-14C)valine, L-(U-14C)leucine, L-(U-14C)histidine and L-(U-14C) phenylalanine by the isolated perfused lactating guinea-pig mammary gland.

1. The incorporation of L-[U-14C]leucine, L[U-14C]histidine and L-[U-14C]phenylalanine into casein secreted during perfusion of isolated guinea-pig mammary glands was demonstrated. 2. The extent of incorporation of label into casein residues was consistent with their being derived from free amino acids of the perfusate plasma. 3. The mean transit time of the amino acids from perfusate into secreted casein was approx. 100 min. 4. Whereas radioactive histidine and phenylalanine were incorporated solely into milk protein, radioactivity from [U-14C]valine was also transferred to CO2 and to an unidentified plasma component, and from [U-14C]leucine to plasma glutamic acid. 5. Evidence from experiments with [U-14C]phenylalanine suggests that, as in rats, but in contrast with ruminant species, guinea-pig mammary tissue does not possess phenyl alanine hydroxylase activity. 6. The results are discussed in relation to the possible role of essential amino acid catabolism in the control of milk-protein synthesis.     

鲆鱼类必需氨基酸的评价比较

为了优化鲆鱼类的营养结构及饲料配制,本文利用氨基酸分析及统计学分析研究了同规格鲆鱼类氨基酸组成模式。结果表明,两者必需氨基酸/总氨基酸为47%~48%、必需氨基酸/非必需氨基酸是87%~93%,相对稳定,符合FAO/WHO氨基酸理想模式;大菱鲆必需氨基酸的组成模式为苏氨酸4.17,异亮氨酸4.06,赖氨酸8.78,苯丙氨酸4.06,蛋氨酸2.72,缬氨酸4.22,亮氨酸8.06,组氨酸2.33,精氨酸5.94。牙鲆必需氨基酸的组成模式为苏氨酸4.10,异亮氨酸4.00,赖氨酸8.85,苯丙氨酸3.70,蛋氨酸2.85,缬氨酸3.95,亮氨酸7.85,组氨酸1.95,精氨酸6.20。鲆鱼类营养价值较高,必需氨基酸组成模式接近。     

Growth Inhibition in Thiobacillus neapolitanus by Histidine, Methionine, Phenylalanine, and Threonine

Thiobacillus neapolitanus, a strict chemoautotroph, is sensitive to the addition of 10(-4)m methionine, histidine, threonine, or phenylalanine to the thiosulfate medium on which it grows. When histidine, threonine, or phenylalanine are added at the time of inoculation, spontaneous mutants tolerant to the three amino acids are selected. These mutants appear to result from a single genetic change; of 18 independently isolated histidine-tolerant mutants, all are also tolerant to phenylalanine and threonine. The uptake of (14)C-phenylalanine into exponentially growing cells of one such mutant is negligible in contrast with the uptake observed in the phenylalanine-sensitive parent. The addition of methionine to the medium slows growth, but spontaneous mutants are not selected. Inhibition of growth by these amino acids is observed only under conditions of amino acid imbalance; the addition of an equimolar mixture of 16 amino acids, in which each component is present at a concentration of 10(-3)m, causes no inhibition. Histidine and threonine inhibition may be released by equimolar amounts of any one of seven amino acids: serine, alanine, glycine, leucine, valine, tryptophan, or tyrosine; histidine inhibition is also released by isoleucine, and threonine inhibition by methionine. None of the inhibiting amino acids inhibits oxidation of thiosulfate in cell suspensions. A group of hexoses, pentoses, and Krebs cycle intermediates were tested for inhibition of growth or release of inhibition by histidine, phenylalanine, or threonine, but no effects, either inhibition or relief of inhibition, were found.     

The utilization of nitrogen for growth in mice fed blends of purified proteins

Reasons for differences in growth of weanling mice fed different blends of purified proteins in diets apparently adequate in indispensable amino acids were investigated. Dietary nitrogen provided at increasing levels from a mixture of casein, gelatin, and zein, or from these plus gliadin and lactalbumin resulted in similar weight gains and efficiency of feed utilization in weanling mice. These responses were always lower (P less than 0.05) than for mice fed the control diet. When diets were based on true digestible nitrogen and amino acids, weight gains and feed efficiency decreased (P less than 0.05) as the dietary nitrogen level increased. High plasma glycine concentrations and high phenylalanine to tyrosine ratios were associated with high dietary glycine levels provided by gelatin. When a mixture of constant proportions of protein sources, predominantly casein, supplied most of the dietary nitrogen, small increases in weight gains and feed efficiency were observed as the nitrogen level in the diet increased. Varying the proportions of sources, which increased the percentage of gelatin, resulted in decreased gains in response to more dietary nitrogen. Replacing the amino acids found in gelatin by crystalline L-amino acids and replacing glycine by glutamic acid improved gains and feed efficiency (P less than 0.05) compared with gelatin-containing diets. These studies demonstrated that glycine at dietary concentrations of approximately 1-2%, either from gelatin or as the free amino acid, inhibited growth and feed utilization of growing mice.     

Structural studies on wheat (Triticum aestivum) proteins lacking phenylalanine and histidine residues.

1. Three very similar proteins, each of approx. 120 amino acid residues but lacking phenylalanine and histidine, were isolated from wheat (Triticum aestivum) flour in sufficient quantities for further structural studies. 2. Each protein, after reduction and carboxymethylation, was cleaved at the three methionine residues with CNBr to give four major peptides, which were isolated. These peptides are suitable for future sequencing studies, as the sums of their amino acid compositions are in good agreement with those of the whole proteins. 3. The N- and C-terminal peptides were identified. 4. Evidence from amino acid analyses, N-terminal amino acids and electrophoretic mobilities of the peptides suggests a high degree of homology between the proteins. Definite differences in C-terminal amino acids and the number of glycine, alanine and arginine residues were found in the C-terminal peptides.     

The effects of added sulphur amino acids, threonine and an ideal amino acid ratio on nitrogen metabolism in mature, overweight dogs

The objectives of this study were to investigate the effects of added essential amino acids in conjunction with a dietary lysine/MJ of 0.72 on nitrogen (N) metabolism in dogs. Treatments were; a control diet, a diet that provided an ideal amino acid profile (IAA), a diet with added total sulphur amino acids (TSAA), and a diet with added TSAA and threonine (TT). Diets were fed to eight overweight, mature, female hounds using a replicated 4 x 4 Latin Square design. Food intake was similar across treatments, however, food N intake was higher (p < 0.001) for TSAA than control, IAA or TT. Nitrogen absorbed was higher (p < 0.01) for TSAA than IAA and control. Urea N excretion was greater for control than TT (p < 0.05). Urine N excretion did not differ between diets. There were no differences in digestibility or N retention of diets. There were no differences in protein turnover, synthesis, or degradation. Blood metabolites were within normal ranges and did not differ due to dietary treatment. Based on the measurements made in this study, there is no benefit for added TSAA, TT or additional EAA in diets for mature dogs formulated to provide a 0.72 g lysine/MJ ME ratio.     

Effects of alkyl polyglycoside, a nonionic surfactant, and forage-to-concentrate ratio on rumen fermentation, amino acid composition of rumen content, bacteria and plasma in goats

In the present study, the effects of different forage-to-concentrate ratios (F:C) and an alkyl polyglycoside (APG) supplementation on parameters of rumen and blood metabolism were investigated in goats. A 2 x 2 factorial experiment was arranged within a 4 x 4 Latin square design (four 22-day periods), using four wether goats equipped with permanent ruminal cannulas. The experimental diets included two F:C levels (40:60 vs. 60:40), and two APG supplementation levels (None or 13 ml APG daily per animal). Rumen contents and blood samples were collected at the end of each period. Dietary F:C alteration affected plasma urea and influenced the proportions of leucine, histidine, arginine, glycine, proline, alanine, valine, phenylalanine, cysteine and tyrosine in rumen content, and the proportions of methionine, threonine and proline in solid-associated bacteria (SAB) significantly. Dietary APG decreased the proportions of valine and phenylalanine in rumen content, and the histidine content of liquid-associated bacteria. The interaction between dietary F:C and APG was significant for the proportions of glycine and alanine in rumen content, and the proportions of lysine and threonine in SAB. The proportion of lysine was greater, but the proportion of threonine was less in SAB for goats fed high F:C diet without APG supplementation. The proportions of plasma free amino acids and glucose concentration were not affected by experimental treatments. These results indicated that dietary APG addition affected the amino acid composition of the rumen content and ruminal bacteria, but this depended on the dietary F:C ratio. It is necessary to validate the effectiveness of dietary APG supplementation in further studies with more animals.     

In vivo regulation of phenylalanine hydroxylation to tyrosine, studied using enrichment in apoB-100

Phenylalanine hydroxylation is necessary for the conversion of phenylalanine to tyrosine and disposal of excess phenylalanine. Studies of in vivo regulation of phenylalanine hydroxylation suffer from the lack of a method to determine intrahepatocyte enrichment of phenylalanine and tyrosine. apoB-100, a hepatic export protein, is synthesized from intrahepatocyte amino acids. We designed an in vivo multi-isotope study, [(15)N]phenylalanine and [2H2]tyrosine to determine rates of phenylalanine hydroxylation from plasma enrichments in free amino acids and apoB-100. For independent verification of apoB-100 as a reflection of enrichment in the intrahepatocyte pool, [1-(13)C]lysine was used as an indicator amino acid (IAA) to measure in vivo changes in protein synthesis in response to tyrosine supplementation. Adult men (n = 6) were fed an amino acid-based diet with low phenylalanine (9 mg.kg(-1).day(-1), 4.54 mumol.kg(-1).,h(-1)) and seven graded intakes of tyrosine from 2.5 (deficient) to 12.5 (excess) mg.kg(-1).day(-1). Gas chromatography-quadrupole mass spectrometry did not detect any tracer in apoB-100 tyrosine. A new and more sensitive method to measure label enrichment in proteins using isotope ratio mass spectrometry demonstrated that phenylalanine hydroxylation measured in apoB-100 decreased linearly in response to increasing tyrosine intake and reached a break point at 6.8 mg.kg(-1).day(-1). IAA oxidation decreased with increased tyrosine intake and reached a break point at 6.0 mg.kg(-1).day(-1). We conclude: apoB-100 is an accurate and useful measure of changes in phenylalanine hydroxylation; the synthesis of tyrosine via phenylalanine hydroxylation is regulated to meet the needs for protein synthesis; and that plasma phenylalanine does not reflect changes in protein synthesis.     

Effect of dietary nutrients on ileal endogenous losses of threonine,cysteine, methionine,lysine, leucine and protein in broiler chicks

An isotope dose technique was utilized (i) to determine endogenous amino acid (AA) and protein losses and (ii) to propose adjusted values for AA requirements. The endogenous flow rate was calculated from the pool of enrichment in plasma AA, assuming similitude to enrichment of endogenous AA. In experiment 1, chicks were orally administered D4-lysine at 2% of estimated lysine intake from 16 to 24 days to find the isotopic steady state of the atom percent excess (APE) of lysine for plasma and jejunal and ileal digesta. The APE of D4-lysine in plasma, jejunal digesta and ileal digesta reached the isotopic steady state at 5.5, 3.4 and 2.0 days, respectively, by using the broken-line model. It was assumed that the isotopic steady state at 5 days identified for D4-lysine is also representative for the ¹⁵N-labeled AA. In experiment 2, chicks were fed diets from 1 to 21 days with increasing levels of fat (6%, 8%, 12%, 13% extract ether), protein (26%, 28.5%, 31% CP) or fiber (14%, 16%, 18% NDF) by adding poultry fat, soybean meal, blended animal protein or barley. Chicks were orally administered ¹⁵N-threonine, ¹⁵N-cysteine, ¹⁵N-methionine, ¹⁵N-lysine and ¹⁵N-leucine at 2% of estimated daily intake for 5 days from 17 to 21 days of age. Dietary nutrients influenced endogenous losses (EL), where dietary fat stimulated EL of lysine (P=0.06), leucine and protein (P=0.07); dietary protein enhanced EL of leucine and protein; and finally the dietary fiber increased EL of leucine. Dietary nutrients also affected apparent ileal digestibility (AID). Dietary fat increased AID of cysteine but decreased AID of lysine. Dietary protein reduced AID of protein, threonine, lysine and leucine, and similarly dietary fiber decreased AID of protein, threonine, methionine, lysine and leucine. In contrast, dietary fat or protein did not affect real ileal digestibility (RID) of protein and AA except threonine and leucine. The dietary fiber reduced the RID of protein, threonine and leucine. This indicate that variations of some endogenous AA and protein losses due to dietary nutrients almost eliminates the effects of RID, and thus the EL coming from the body should be utilized to adjust the AA requirement instead of changing the true digestible nutrients of ingredients. The present data suggest that 5 days’ feeding labeled AA was enough to reach the isotopic steady state and AA requirements should be adjusted when additional dietary protein, fat or fiber is fed.     

Changes in plasma amino acid concentrations with increasing age in patients with propionic acidemia

The objective of the study is to analyze plasma amino acid concentrations in propionic acidemia (PA) for the purpose of elucidating possible correlations between propionyl-CoA carboxylase deficiency and distinct amino acid behavior. Plasma concentrations of 19 amino acids were measured in 240 random samples from 11 patients (6 families) with enzymatically and/or genetically proven propionic acidemia (sampling period, January 2001–December 2007). They were compared with reference values from the literature and correlated with age using the Pearson correlation coefficient test. Decreased plasma concentrations were observed for glutamine, histidine, threonine, valine, isoleucine, leucine, phenylalanine and arginine. Levels of glycine, alanine and aspartate were elevated, while values of serine, asparagine, ornithine and glutamate were normal. For lysine, proline and methionine a clear association was not possible. Significant correlations with age were observed for 13 amino acids (positive correlation: asparagine, glutamine, proline, alanine, histidine, threonine, methionine, arginine; negative correlation: leucine, phenylalanine, ornithine, glutamate and aspartate). This study gives new insight over long-term changes in plasma amino acid concentrations and may provide options for future therapies (e.g., substitution of anaplerotic substances) in PA patients.     

Effect of the composition of branched chain amino acids, taurine, and tryptophan on the amino acid metabolism in experimental models of alcoholism

Ethanol withdrawal after forced alcoholization of rats according to Majchrowicz led to the development of amino acid imbalance in the pool of free amino acids in the liver (increasing levels of alanine, aspartate, glutamate, glutamine and histidine, decreasing levels of glycine, lysine, threonine and taurine) and blood plasma (increasing levels of tyrosine and alanine, decreasing levels of most glycogen aminoacids, branched-chain aminoacids and Lys). Less profound changes were observed after prolonged alcohol intoxication (decreasing levels of alanine, ornitine, citrulline and increasing level of Glu in liver, increasing levels of sulfur-containing compounds, Asp and Lys in blood plasma). Amino acid mixture which contained branched-chain amino acids, taurine and tryptophan administered intragastrically was found to correct levels of sulfur-containing amino acids, threonine, lysine and isoleucine after ethanol withdrawal and to eliminate disorders in urea cycle, exchange of threonine, glycine and phenylalanine after prolonged alcohol intoxication.     

Metabolism of threonine in newborn infants

Threonine kinetics, threonine oxidative pathway, and the relationship between threonine and whole body protein turnover were quantified in 10 healthy term infants during the first 48 h after birth. The kinetic data were obtained 6 h after the last feed (fasting) and in response to formula feeding, using [U-(13)C(4),(15)N]threonine, [(2)H(5)]phenylalanine, and [(15)N]glycine tracers. The rate of carbon dioxide production (Vco(2)) and (13)C enrichment of the expired CO(2) were measured to quantify the rate of oxidation of threonine. The rate of appearance (R(a)) of threonine (136 +/- 37 micromol.kg(-1).h(-1)) was higher in newborn infants than that reported in adults. Formula feeding resulted in a significant decrease in threonine R(a) (P < 0.05). A significant positive correlation was seen between phenylalanine R(a) and threonine R(a), both during fasting and after formula feeding (r(2) = 0.65). In contrast to a 1:1 ratio of threonine and phenylalanine in mixed muscle protein, threonine R(a) relative to phenylalanine R(a) was 2.2 +/- 0.4. The fractional rate of threonine flux oxidized was 20% during fasting and 26% (P < 0.05) in response to nutrient administration. There was a significant correlation between plasma threonine concentration and threonine oxidation (r(2) = 0.75). No measurable incorporation of threonine in plasma glycine was seen. These data suggest that threonine is exclusively degraded by the glycine-independent serine/threonine dehydratase pathway. A higher flux of threonine relative to phenylalanine indicates higher turnover of threonine enriched proteins.     

Influence of glucogenic amino acids on the hepatic metabolism of threonine.

The supplementation of a low-protein diet with L-threonine leads to a marked accumulation of threonine in plasma and liver, whereas increasing dietary protein generally leads to an induction of threonine dehydratase in the liver, hence depressed availability for extrasplanchnic tissues. The aim of the present study was, thus, to further investigate the factors which control the utilization of threonine by the liver. Increasing the dietary supply of threonine led to parallel increases in the afferent and hepatic concentrations and in the rate of utilization by the liver; however, the fractional extraction tended to decrease. It appears that the addition of a mixture of glucogenic amino acids to the diet prevented the accumulation of threonine in plasma induced by exogenous threonine. The glucogenic amino acids increased the fractional hepatic uptake of threonine, and counteracted its accumulation in the liver. These effects reflect the fact that the glucogenic amino acids elicited a potent induction of the threonine dehydratase, whereas threonine alone was uneffective. Our results suggest that, besides the well-established effect of glucogenic conditions, the availability of some glucogenic amino acids is an important factor in the control of threonine catabolism.     

Evaluation of optimum lysine and threonine supplements to a wheat and barley-based diet in rats

Experiments were conducted on growing male SPF-rats to study the optimum supplementation with essential amino acids of diets containing wheat and barley (1.4:1) as the only source of nitrogen. In growth and balance experiments comprising 30 and 17 combinations of L-lysine and L-threonine, respectively, the concentrations of the two amino acids corresponding to maximum body weight gain, feed conversion efficiency, biological value of protein and net protein utilization were calculated using multiple regression analysis. Addition of lysine and threonine to the basal diet markedly improved the nutritional value of cereal proteins. The optimum concentrations found were 0.69–0.70% total dietary lysine and 0.52–0.55% total dietary threonine. Statistical analysis showed that the number of observations used for the estimation of regression functions in the growth experiment could be reduced to ca. 100 without substantially affecting precision.     

Amino-acid synthesis in adult Dacus oleae (Gmelin) (Diptera Tephritidae) determined with [U-14C] glucose

The ability of adult Dacus oleae for amino-acid synthesis from [U-14C] glucose was investigated. The relatively high specific activity radiometric measurements indicated that both sexes were able to synthesize the amino acids: alanine, aspartic acid, cystine, glutamic acid, glycine, hydroxyproline, proline and tyrosine; therefore, these amino acids are considered as nutritionally dispensable for D. oleae. On the other hand, the amino acids: arginine, histidine, leucine, isoleucine, lysine, methionine, phenylalanine, serine, threonine, and valine, showed a very low specific activity and therefore are considered as nutritionally indispensable. It was not possible to conclude about tryptophane, since the acid hydrolysis destroyed this amino acid.     

Changes in cerebrospinal fluid and plasma amino acid concentrations with elevated dietary protein concentration in dogs with portacaval shunts

Effects of dietary protein concentration on plasma and cerebrospinal fluid (CSF) amino acids (AA) in dogs with portacaval shunts (PCS) were examined. An 18% protein purified diet (18P) was fed to 4 PCS dogs and 2 controls; at week 10, 2 of the PCS dogs were switched to 36% protein (36P) until week 28. Effects of the diet switch on plasma and CSF AA in 8 normal dogs were determined in another experiment. Neither surgery nor protein level significantly affected average food intake (weeks 10-28). Plasma amino acid patterns typical of PCS animals were observed: phenylalanine and tyrosine increased and branched chain AA decreased with shunting (p less than 0.05). Plasma phenylalanine increased further with 36P in PCS dogs (p less than 0.05), but was not affected by dietary protein concentration in controls. With 36P: CSF arginine, serine, histidine, tryptophan, phenylalanine, glutamate and glutamine increased in PCS dogs; but only arginine decreased in CSF of controls (p less than 0.05). In PCS dogs, significant CSF AA changes with elevated dietary protein were unrelated to plasma AA changes.     

Indispensable amino acid concentrations decrease in tissues of stomachless fish,common carp in response to free amino acid- or peptide-based diets

Summary. The premise that free amino acid or dipeptide based diets will resolve the nutritional inadequacy of formulated feeds for larval and juvenile fish and improve utilization of nitrogen in comparison to protein-based diets was tested in stomachless fish, common carp (Cyprinus carpio L.) larvae. We examined the postprandial whole body free amino acid (FAA) pool in fish that were offered a FAA mixture based diet for the duration of 2 or 4 weeks. We found that the total amount and all indispensable amino acids concentrations in the whole body decreased after a meal. We then fed juvenile carp with dietary amino acids provided in the FAA, dipeptide (PP), or protein (live feed organisms; brine shrimp Artemia salina nauplii, AS) forms. Histidine concentrations in the whole fish body increased in all dietary groups after feeding whereas all other indispensable amino acids decreased in FAA and PP groups in comparison to the AS group. Taurine appears to be the major osmotic pressure balancing free amino acid in larval freshwater fish which may indicate a conditional requirement. We present the first evidence in larval fish that in response to synthetic FAA and PP diets, the whole body indispensable free AA concentrations decreased after feeding. This study shows that amino acids given entirely as FAA or PP cannot sustain stomachless larval fish growth, and may result in depletion of body indispensable AA and most of dispensable AA. The understanding of these responses will determine necessary changes in diet formulations that prevent accelerated excretion of amino acids without protein synthesis.     

Amino acid imbalance in the liquid-fed lamb.

Eleven Poll Dorset times Merino crossbred female lambs 4 weeks of age were trained to suck liquid diets from bottles. In three separate experiments liquid diets providing 14-2% (expt 1) 10-6% (expt 2) or 8-0% (expt 3) of gross energy as protein and amino acids were fed. Responses in voluntary intake, growth rate and changes in plasma amino acid concentrations were studied when complete or incomplete mixtures of amino acids were added to the liquid diet. These mixtures supplied either: (1) all amino acids in quantities to bring the total of protein plus amino acids to provide more than 20% of dietary gross energy, the amino acids being provided in proportions estimated to meet adequately the lamb's requirements ('complete'); or (2) as the same total amount of amino acids but with the amino acid supplement devoid of threonine ('low-threonine', expts 1 and 2) or isoleucine ('low isoleucine', expt 3). In experiment 1, there was no food intake or growth depression after feeding the amino acid mixture lacking threonine. In both experiments 2 and 3, voluntary food intake was depressed to about 50% of that observed in lambs fed the low protein diet, when the amino acid mixture devoid of threonine or of isoleucine, respectively, was fed. Addition of the missing amino acid to the low threonine and low isoleucine diets resulted in recovery of voluntary intake in experiments 2 and 3 respectively, but no significant improvement above that found after feeding the low protein (basal) diet. In experiments 1 and 2, after feeding the low threonine diet the threonine concentration in the blood plasma decreased markedly, while concentrations of total amino acids were elevated. Although there was no improvement in growth or food intake, the feeding of the diet containing the complete amino acid mixture resulted in an elevation of all essential amino acids including threonin. Similarly in experiment 3, plasma isoleucine concentration decreased in the lambs fed the isoleucine imbalanced diet. Results indicate that the suckled, preruminant lamb exhibits sensitivity to dietary amino acid imbalance, in a manner analogous to that found in simple-stomached animals. These results also clearly illustrate a depression in food intake associated with the deletion of a specific essential nutrient from the diet of the lamb.     

Some Effects of Protein Deficiency in Young Growing Pigs. II. Blood Plasma Free Amino Acids

The influence of protein deficiency, rehabilitation and total starvation on the free amino acid levels in the blood plasma of pigs has been investigated. It was found that the concentration of most amino acids was reduced during protein deficiency. The levels of leucine, isoleucine and valine were diminished by the greatest proportion, followed by threonine, tyrosine and citrulline. During the first few weeks of protein deficiency the levels of lysine, histidine and arginine were slightly increased, but later decreased below control values. Concentrations of glycine and alanine were altered in a similar way except that the initial increase was much more pronounced. The concentrations of most of these amino acids returned to control levels after rehabilitation. Total starvation led to an increase in concentration of leucine, isoleucine, valine, threonine and to a smaller extent phenylalanine, lysine, citrulline and arginine. The concentration of glycine, alanine and glutamic acid were very much reduced. The level of urea in the circulation dropped reversibly during protein deficiency and increased very much during total starvation.