Response to elemental sulfur by calves and sheep fed purified diets

Free amino acid profiles in plasma and liver as well as body, organ and gastrointestinal growth were compared in 20 weanling bulls (four per treatment) fed diets deficient (.04%), excessive (.94 and 1.72%) or adequate (.34%) in S. Body, organ and gastrointestinal comparisons also were made with yearling rams fed .04 and .34% S diets. The .34% S diet was fed at two levels, one ad libitum, the other in amounts equal on a body weight.75 basis to that consumed by animals fed the .04% S diet ad libitum. Animals were allowed to consume other diets ad libitum. The calves fed the .04% S diet had negative S, but slightly positive N, balance and were unable to maintain body weight. As dietary S content was increased, plasma and liver methionine increased linearly. An increased histidine in plasma of calves fed the .04% S diet may be due to reduced intake because the calves restricted-fed the .34% S diet also had high plasma histidine. Plasma citrulline, cystine, serine and total nonessential amino acids decreased markedly as dietary S intake became adequate. Intermediate S diets resulted in reduced concentrations of plasma alanine, serine, proline and total nonessential amino acids. Calves restricted-fed the .34% S diet were the most efficient in retaining N with less urinary N. Excesses of S were not detrimental to growth, but plasma valine increased linearly as S intake increased. The S deficiency in calves reduced the ratio of the rumen-reticulum tissue to body weight, and in rams it reduced the ratio of gastrointestinal tissue and preintestinal tissue to body weight. Per kilogram of intestinal-free body weight, there was a linear decrease in liver and testes but an increase in adrenals as S was decreased for calves. The kidney, adrenals and pituitary were increased by S deficiency in rams. Of the amino acids assayed, only methionine from the plasma and liver in calves reflected both an excess and a deficiency of S independent of feed intake effects.     

Influence of fermentable fiber on small intestinal dimensions and transport of glucose and proline in dogs

OBJECTIVE: To determine whether intestinal dimensions and nutrient absorption are influenced by different types of dietary fiber. ANIMALS: 10 adult Beagles of both sexes. PROCEDURE: Dogs were randomly assigned to 2 groups and fed a diet with fermentable fibers (beet pulp and oligofructose) or a nonfermentable fiber (cellulose) for 6 weeks. Effects of the diets on small intestinal dimensions were measured, and transport rates for glucose and proline were determined. Kinetics of glucose and proline uptake were defined in the proximal and middle regions of the small intestine, respectively. RESULTS: Small intestines of dogs fed fermentable fiber had 28% more nominal surface area and 37% more mucosal mass, were 35% heavier, and had 95% higher capacity for carrier-mediated glucose uptake than those of dogs fed a diet with cellulose. Differences were more pronounced in the proximal portion of the intestine. CONCLUSIONS AND CLINICAL RELEVANCE: Diets containing fermentable fibers increase small intestinal dimensions and the capacity for nutrient absorption in dogs. These changes may reduce the risk of enteric infections or aid in treatment of intestinal diseases, particularly those involving reduced nutrient absorption.     

Dietary requirements of synthesizable amino acids by animals:a paradigm shift in protein nutrition

Amino acids are building blocks for proteins in all animals.Based on growth or nitrogen balance,amino acids were traditionally classified as nutritionally essential or nonessential for mammals,birds and fish.It was assumed that all the "nutritionally nonessential amino acids(NEAA)" were synthesized sufficiently in the body to meet the needs for maximal growth and optimal health.However,careful analysis of the scientific literature reveals that over the past century there has not been compelling experimental evidence to support this assumption.NEAA(e.g.,glutamine,glutamate,proline,glycine and arginine) play important roles in regulating gene expression,cell signaling,antioxidative responses,fertility,neurotransmission,and immunity.Additionally,glutamate,glutamine and aspartate are major metabolic fuels for the small intestine to maintain its digestive function and to protect the integrity of the intestinal mucosa.Thus,diets for animals must contain all NEAA to optimize their survival,growth,development,reproduction,and health.Furthermore,NEAA should be taken into consideration in revising the "ideal protein" concept that is currently used to formulate swine and poultry diets.Adequate provision of all amino acids(including NEAA) in diets enhances the efficiency of animal production.In this regard,amino acids should not be classified as nutritionally essential or nonessential in animal or human nutrition.The new Texas A&M University’s optimal ratios of dietary amino acids for swine and chickens are expected to beneficially reduce dietary protein content and improve the efficiency of their nutrient utilization,growth,and production performance.     

Dietary requirements of synthesizable amino acids by animals: a paradigm shift in protein nutrition

Amino acids are building blocks for proteins in all animals. Based on growth or nitrogen balance, amino acids were traditionally classified as nutritionally essential or nonessential for mammals, birds and fish. It was assumed that all the “nutritionally nonessential amino acids (NEAA)” were synthesized sufficiently in the body to meet the needs for maximal growth and optimal health. However, careful analysis of the scientific literature reveals that over the past century there has not been compelling experimental evidence to support this assumption. NEAA (e.g., glutamine, glutamate, proline, glycine and arginine) play important roles in regulating gene expression, cell signaling, antioxidative responses, fertility, neurotransmission, and immunity. Additionally, glutamate, glutamine and aspartate are major metabolic fuels for the small intestine to maintain its digestive function and to protect the integrity of the intestinal mucosa. Thus, diets for animals must contain all NEAA to optimize their survival, growth, development, reproduction, and health. Furthermore, NEAA should be taken into consideration in revising the “ideal protein” concept that is currently used to formulate swine and poultry diets. Adequate provision of all amino acids (including NEAA) in diets enhances the efficiency of animal production. In this regard, amino acids should not be classified as nutritionally essential or nonessential in animal or human nutrition. The new Texas A&M University’s optimal ratios of dietary amino acids for swine and chickens are expected to beneficially reduce dietary protein content and improve the efficiency of their nutrient utilization, growth, and production performance.     

The effect of proteinase inhibitors in rats. 1. Report. Effect of a short-term application on the N balance, the free amino acids in liver and muscles and the biological half-life of the intestinal tissue proteins]

Short-term trials with a triazin derivative and a peptide aldehyde were carried out to investigate the in-vivo administration of proteinase inhibitors in rats for improving the N balance of the animals. The results of N balances suggest that the peptide aldehyde may be regarded as a promising substance that may be used to increase the rate of utilization of the absorbed N in the intermediary metabolism. The short-term use of both active compounds did not affect the true N digestibility. The two compounds did not influence the concentration of free amino acids in the liver and muscle tissue under the experimental feeding conditions used. Similarly, tests of the biological half-life of proteins taken from the small and large intestine did not reveal any changes due to the presence of the inhibitors. Animals receiving a protein-free diet exhibited longer half-life periods for proteins from the small and large intestine compared with animals of the other groups. A protein-free nutrition of the animals caused a general increase in the levels of free non-essential amino acids in the liver. This was accompanied by a simultaneous decrease in essential amino acids. The same type of nutrition led to a general decline in the concentration of free amino acids in muscular tissue, particularly of the essential amino acids. High-protein nutrition led especially to an increase in the concentration of branched-chain amino acids in both types of tissues investigated.     

Amino acid pattern in the bodies and several organs of broilers fed different provisions with tryptophan and neutral amino acids

Carcasses and organs of 36 broiler chicks originating from an extensive fattening experiment with differing proportions of tryptophan (0.65 and 0.93 g/16 g N) to the neutral amino acids (15.2, 18.3 and 22.0 g/16 g N) in feed were analyzed for amino acid contents. Aside from the whole carcasses, a selected muscle (M. fibularis longus), liver, small intestine, and brain were prepared from the animals and analyzed. The organ weights differed according to the live-weights with the exception of the brain, where no group differences were measured. The patterns of amino acids of carcasses and organs remained nearly constant with differing amino acid supply. The only remarkable effect was the increase of the proportions of proline and hydroxyproline in the carcass protein from 6.4 to 7.4 and from 1.6 to 1.8%, respectively, with the higher tryptophan supply indicating increasing proportions of connective tissue. No relationship between weight gain and collagen content (calculated from hydroxyproline content) could be detected. The frequently supposed antagonism between tryptophan and the neutral amino acids, especially at the border of blood and brain, caused no reduction in tryptophan content of brain with increasing supply of neutral amino acids. There was, however, a significant depression of the development of the animals and the other inner organs.     

合成氨基酸对肉鸡肠道功能的改善作用

鸡球虫病、坏死性肠炎等肠道感染可能对消化道内源性氨基酸损失产生较大影响。虽然对这一课题的了解不多，但相关文献报道了这些疾病对氨基酸表观回肠消化率的影响。在确定肠内氨基酸流动时必须考虑多种因素，包括肉鸡的年龄、是否有病原体、肠内氨基酸代谢等。胃肠道和肝脏共同承担向外周血释放氨基酸的任务，这些氨基酸是支持蛋白质合成所必需的。一般来说，肠道是氨基酸代谢反应的一个非常活跃的器官系统，它首先会满足自身对氨基酸的需求，然后才会将氨基酸输送到机体其他部分。因此，本综述旨在讨论影响肠内氨基酸流动的因素及日粮氨基酸和肠道感染对氨基酸利用和代谢的影响。     

Research Progress on Effects of Proline on Reproductive Performance of Sows

Proline is a cyclic α-imino acids,meanwhile it also can be considered as a functional amino acid for mammals and plays an important role in protein synthesis,organism metabolism,wound healing,anti-oxidant and immune reactions. The studys have found that extra dietary supplementation of moderated proline has great significance in improving the growth and development of conceptus,piglets, embryo,mammary gland and placenta of sows,at the same time it also can prevent intrauterine growth restriction. The author reviewed structure characters and physicochemical properties,anabolism and catabolism of proline,and especially focused on its effects on the reproductive performance of pregnancy sows and potential regulation mechanism aiming to provide some help for the researchers in the field of sows.     

Effect of nonessential amino acids on nitrogen retention in growing pigs fed on a protein-free diet supplemented with sulphur amino acids, threonine and tryptophan

Two N balance experiments were conducted on growing pigs to study the effect of essential and nonessential amino acids added to a protein-free diet on N retention. In Expt. 1, the addition of sulphur amino acids, threonine and tryptophan to a protein-free diet at levels two times the maintenance requirements reduced (p > 0.1) daily N loss from –131 to –108 mg/kg^0.75. A further addition of nonessential amino acids equivalent to 250 mg N/kg^0.75/d resulted in a marked increase (p < 0.01) in daily N retention to 28 mg/kg^0.75. In Expt. 2, nonessential amino acids were added to a protein-free diet supplemented with sulphur amino acids, threonine and tryptophan at levels corresponding to 100, 200 and 300 mg N/kg^0.75/d. N retention increased linearly as dietary nonessential N increased. The slope of the best-fit regression line indicated that the marginal efficiency of nonessential N utilization for protein accretion was 0.26. The results suggest that nonessential amino acids may be a limiting factor for the re-utilization of amino acids released by body protein breakdown or that they may serve as precursors for de novo synthesis of amino acids by gut microorganisms, thus contributing to the amino acid requirements of the pig.     

脯氨酸对母猪繁殖性能影响的研究进展

脯氨酸为环状的α-亚氨基酸,同时也是哺乳动物的功能性氨基酸,在蛋白合成、机体新陈代谢、伤口愈合、抗氧化反应和免疫反应中发挥着重要作用。研究发现,添加适量的外源性脯氨酸,可以促进胎儿与仔猪的生长发育、预防胎儿宫内生长迟缓,同时对胚胎、乳腺及胎盘生长发育具有重要的意义。作者阐述了脯氨酸的结构特征、理化性质、合成和分解代谢,重点介绍了脯氨酸对母猪繁殖性能的影响及其潜在的机制,为进一步研究脯氨酸对母猪繁育的影响提供参考。     

NaCl胁迫对苦马豆苗期脯氨酸代谢的影响

以苦马豆(Swainsonia salsula Taub.)为试验材料,通过8个不同浓度(0(CK),80,160,240,320,400,480和560 mmol·L^-1 )NaCl胁迫,对苦马豆苗期脯氨酸(Pro)含量及吡咯啉-5-羧酸合成酶(P5CS)、鸟氨酸δ-氨基转移酶(δ-OAT)和脯氨酸脱氢酶(ProDH)活性进行测定,探讨苦马豆对NaCl胁迫的耐受程度和脯氨酸代谢与其耐盐性的关系,以期揭示苦马豆苗期脯氨酸代谢规律,为进一步研究其耐盐性奠定基础。结果表明:在NaCl胁迫下,苦马豆植株根冠比呈现先升高后降低的趋势,苦马豆中脯氨酸含量随NaCl浓度的升高而增大(P＜0.05),在400 mmol·L^-1 NaCl胁迫时,脯氨酸代谢最为旺盛;400 mmol·L^-1 NaCl浓度为苦马豆耐盐阈值。随NaCl浓度的不断升高,苦马豆苗期脯氨酸合成由以鸟氨酸途径为主逐渐转变为以谷氨酸途径为主,鸟氨酸途径为辅的协同合成。     

盐胁迫对碱地风毛菊苗期脯氨酸代谢的影响

通过对碱地风毛菊(Saussurea runcinata)苗期分别以NaCl和Na₂SO₄进行胁迫,设6个浓度和1个对照,测定其脯氨酸含量及δ-氨基转移酶、吡咯啉-5-羧酸合成酶和脯氨酸脱氢酶活性,以探讨其苗期耐盐性及脯氨酸代谢途径,并为盐碱地植被恢复与改良提供依据。结果表明:NaCl和Na₂SO₄胁迫下,碱地风毛菊的脯氨酸含量随NaCl和Na₂SO₄胁迫浓度增加而增高,在盐胁迫下,碱地风毛菊的脯氨酸合成途径以鸟氨酸途径为主;且在300mmol·L^-1的盐浓度胁迫下碱地风毛菊苗期的脯氨酸代谢最为旺盛,其对NaCl胁迫的耐性较高。     

Action of proteinase inhibitors in rats. 3. Influence of leupeptin on the rate of protein synthesis and the intracellular protein degradation by use of a test system including constant infusion of labelled amino acids, estimation of 3-methyl-histidine excretion and a triple-labelling technique

Male Wistar rats (initial body weight 90 g) were fed ad libitum a whole-egg diet containing 10,5% crude protein. The animals of the experimental group received in each case of 1 mg leupeptin per 100 g of body weight in 12 hrs-intervals by i. p.-injection (3 days of treatment). Control animals got a leupeptin free solution. In addition, lysine dihydrochloride-alpha-15N was applied during the first three days of experiment to all animals and the nitrogen balance was determined. Urine from the N-Balance collection was analysed for 3-methyl-histidine excretion in order to calculate the degradation rate of myofibrillar proteins. On the fourth day the fractional rate of protein synthesis in several organs was estimated using the continuous infusion technique with 14C-leucine and 14C-lysine. The apparent biological half-lives of tissue protein were determined by a triple labelling technique, with (14C)-guanidino-L-arginine, L-5-3H-arginine and 15N-Lysine. The short-term treatment 3 days) with leupeptin did not affect the weight gain, the apparent digestibility of nitrogen and the N-balance. The fractional rate of protein synthesis was highest in the small intestine followed by the large intestine, liver and skeletal muscle and no influence of leupeptin treatment was observed. Furthermore no differences in the degradation rates of myofibrillar proteins between treated and untreated animals were found. The 3-methyl-histidine excretion via urine was 1.44 mg . kg-1 day-1 in both groups corresponding to a fractional rate of degradation of myofibrillar proteins of 2,5% per day. Apparent half-lives of tissue proteins in the small intestine, large intestine and liver, respectively, were shortest when estimated from the decay curves for the 14C-label and longest from the curves for the 15N-label. Leupeptin treatment resulted in prolonged apparent half-lives of the proteins in the large intestine and of the slowly turning over proteins in the liver. However, this effect seems to be caused rather by an increased reutilization of labelled amino acids than by a decreased protein degradation. Before continuing this kind of work the rate of uptake of injected leupeptine into tissues has to be investigated. Studies dealing with the in vivo action of proteinase inhibitors on protein metabolism have to include estimations of N-balance, protein synthesis rate, intracellular degradation rate of proteins as well as amino acid reutilization.     

Nitrogen balance and amino acid disappearance from the small intestine in calves fed soybean meal-, toasted soybean meal- or corn gluten meal-supplemented diets

Nine crossbred (Hereford X Angus X Charolais) heifer calves (139 kg; 6 mo of age) with abomasal and ileal cannulas were used in a repeated design to evaluate N balance and amino acid disappearance in the small intestine. Calves were fed either soybean meal (SBM), toasted SBM (TSBM, 93 C for 90 min) or corn gluten meal (CGM) as supplemental protein sources. Each calf received approximately 83 g N/d from a cottonseed hull-corn based diet with 43% of the total dietary N supplied by the test proteins. Each experimental period consisted of a 10-d adaptation, 6-d digesta collection and 5-d excreta collection. Following the first 21-d period, calves were randomly re-allotted to treatment and the sampling process was repeated. Dry matter (64%) and N digestibilities (61%) and N retention (36.8 g/d) were similar (P greater than .10) among treatments. Nitrogen flow to the small intestine was similar for TSBM- and CGM-fed calves (119.1 g/d), but greater (P less than .01) than for those offered SBM (96.3 g/d). Offering TSBM and CGM resulted in greater quantities of essential, nonessential and total amino acids reaching the abomasum compared with SBM. Total amino acid flow to the small intestine was 100, 120 and 128% of intake for SBM, TSBM and CGM, respectively. Numerically, amino acid digestibility was lower in CGM-fed calves. Methionine digestibility was highest (64.6%), while histidine was lowest (43.7%). Feeding CGM may result in greater quantities of amino acids reaching the small intestine; however, several of these amino acids may be less digestible than for TSBM.     

Biochemical and physiological bases for utilization of dietary amino acids by young Pigs

Protein is quantitatively the most expensive nutrient in swine diets. Hence it is imperative to understand the physiological roles played by amino acids in growth, development, lactation, reproduction, and health of pigs to improve their protein nutrition and reduce the costs of pork production. Due to incomplete knowledge of amino acid biochemistry and nutrition, it was traditionally assumed that neonatal, post-weaning, growing-finishing, and gestating pigs could synthesize sufficient amounts of all "nutritionally nonessential amino acids" (NEAA) to support maximum production performance. Therefore, over the past 50 years, much emphasis has been placed on dietary requirements of nutritionally essential amino acids as building blocks for tissue proteins. However, a large body of literature shows that NEAA, particularly glutamine, glutamate, arginine and proline regulate physiological functions via cell signaling pathways, such as mammalian target of rapamycin, AMP-activated protein kinase, extracellular signal-related kinase, Jun kinase, mitogen-activated protein kinase, and NEAA-derived gaseous molecules (e.g., nitric oxide, carbon monoxide, and hydrogen sulfide). Available evidence shows that under current feeding programs, only 70% and 55% of dietary amino acids are deposited as tissue proteins in 14-day-old sow-reared piglets and in 30-day-old pigs weaned at 21 days of age, respectively. Therefore, there is an urgent need to understand the roles and dietary requirements of NEAA in swine nutrition. This review highlights the basic biochemistry and physiology of absorption and utilization of amino acids in young pigs to enhance the efficacy of utilization of dietary protein and to minimize excretion of nitrogenous wastes from the body.     

Arginine catabolism in lactating porcine mammary tissue

In vivo studies have shown that the uptake of plasma arginine by the lactating porcine mammary gland greatly exceeds the output of arginine in milk, but little is known about the metabolic fate of arginine in this organ. The objective of this study was to quantify arginine catabolism via arginase and nitric oxide synthase pathways in the mammary tissue of sows on d 28 of lactation. Mammary tissue slices (approximately 60 mg) were incubated at 37 degrees C for 1 h in 2 mL of Krebs bicarbonate buffer containing 0.5 or 2 mM L-[U-14C]arginine, and arginine metabolites were measured using HPLC and radiochemical techniques. Rates of arginine utilization were similar to rates of urea production. Proline, ornithine, urea, glutamate, glutamine, CO2 and polyamines (putrescine + spermidine + spermine) were formed from arginine, accounting for 46, 31, 17, 2.3, 1.5, 0.22, and 0.30%, respectively, of the metabolized arginine carbons. Relatively small amounts of arginine were utilized for nitric oxide and citrulline synthesis, with citrulline accounting for 2% of the metabolized arginine carbons. Production of all arginine metabolites increased with increasing extracellular arginine concentrations from 0.5 to 2 mM, indicating a high capacity for arginine degradation. Consistent with the metabolic findings, the activities of arginases, ornithine aminotransferase, and pyrroline-5-carboxylate reductase were high, whereas those of pyrroline-5-carboxylate dehydrogenase, ornithine decarboxylase, and nitric oxide synthases were relatively low, and there was no proline oxidase, ornithine carbamoyltransferase or pyrroline-5-carboxylase synthase activity in the mammary tissue. Our results demonstrate for the first time that proline, ornithine, and urea were the major products of arginine catabolism via the arginase pathway in lactating porcine mammary tissue and provide a biochemical basis to explain a relative enrichment of proline but a relative deficiency of arginine in sow's milk.     

A review of the role of acid-base balance in amino acid nutrition

Acid-base balance and amino acid metabolism are intimately related. Changes in acid-base balance influence the metabolic fate of many amino acids. Also, acid-base homeostasis is achieved in part by alteration of amino acid metabolism, not only in the kidney, but also in liver, muscle and splanchnic tissue. Glutamine is the primary amino acid involved in renal ammonia-genesis, a process intimately related to acid excretion. The metabolism of other amino acids, such a serine, glycine and the branched-chain amino acids, also appears to be influenced by acid-base balance. Conversely, the metabolic fate of various amino acids will influence the daily acid load experienced by the animal. Oxidation of amino acids contributes to the total acid and base load imposed on the pig. The basic (cationic) amino acids (lysine, arginine and histidine) yield neutral end-products plus a proton; sulfur (methionine and cysteine) amino acids are also acidogenic because they generate sulfuric acid when oxidized. The dicarboxylic (anionic) amino acids (aspartate and glutamate, but not asparagine and glutamine) consume acid when oxidized and thus reduce the acid load of the diet. Acid-base balance and related phenomena are discussed in the context of practical and metabolic aspects of amino acid nutrition.     

New concepts in fetal and placental amino acid metabolism.

Fetal amino acid nutrition and metabolism have been studied primarily in pregnant sheep. The umbilical uptake of amino acids changes during gestation, but at both mid- and late gestation the total supply exceeds that required for growth. Weight-specific protein synthetic rate decreases with increasing gestational age, and these changes are proportional to the changes in metabolic rate. The use of multiple tracer methodology coupled with measurement of net tracer fluxes into and out of fetal and placental tissues can be used to delineate amino acid metabolism in considerable detail. Such studies demonstrate that even essential amino acids can be oxidized extensively by the fetus. The oxidation rate of leucine exceeds its rate of accretion in tissue proteins. Glycine metabolism is unique in several ways; there is a large umbilical uptake of glycine without a measurable uterine uptake. In late gestation there is no significant umbilical uptake of serine, although there is a significant uterine uptake, suggesting net uteroplacental utilization. Glycine is oxidized within the fetal liver and used for serum production. The interorgan exchange of amino acids between the fetal liver and placenta is clearly of major importance for serine and glycine metabolism and is likely to be of major importance for most nonessential amino acids.     

Relationship between the quality of dietary proteins and the functional status of the adrenal cortex. 5. Content of corticosterone and cortisol in the liver and in the mucosa of the small intestine of rats fed with proteins of various quality (estimation of binding capacity for corticosteroids)]

Relationships between the Quality of Dietary Proteins and the Functional State of the Adrenal Cortex. (5) Content of Corticosterone and Cortisol in the Liver and in the Mucosa of the Small Intestine of Rats Fed Proteins of Varying Quality (Estimation of the Binding Capacity for Corticosteroids). Growing male Wistar rats were used to investigate in which way the quality of dietary proteins (maize gluten and maize gluten supplemented with amino acids) influenced the content of corticosteroids in the liver and in the mucosa of the small intestine of untreated rats (N), adrenalectomized animals (AE) and animals treated with corticosteroids (N + S). In AE animals the content of corticosteroids in the tissues was very low. In N + S animals of both dietary groups the mucosa of the small intestine contained more corticosteroids than the liver; the content of corticosteroids in the mucosa, however, was also found to vary in dependence upon the diet fed. The mucosa of N + S animals receiving dietary proteins of high quality contained more corticosteroids; this indicates a higher binding capacity of the mucosa for corticosteroids.     

Incorporation of nitrogen-15 from dietary [15N] diammonium citrate into amino acids of liver and muscle proteins in germfree and specific-pathogen-free neonatal pigs

Incorporation of 15N from dietary [15N]diammonium citrate ([15N]DAC) into amino acids isolated from hydrolyzed tissue proteins was investigated in the presence or absence of intestinal flora in neonatal pigs. The 15N was incorporated into all of the essential and nonessential amino acids from liver and muscles in one of two germfree pigs and two specific-pathogen-free pigs which were killed on the 5th day after the administration of [15N]DAC. But, a higher 15N concentration than natural abundance of 15N was not detected in histidine, lysine, and threonine from these tissues in another germfree pig killed the next day. Nitrogen transfer from DAC into all amino acids, including these three essential amino acids, may be possible in the specific-pathogen-free pig and even in the germfree pig.