饲粮电解质平衡对动物营养物质代谢的影响

饲粮电解质平衡状况可影响动物机体酸碱平衡,进而影响营养物质的消化吸收率,还可通过改变一些酶的活性而影响氨基酸等养分的代谢利用。     

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.     

The influence of the pH of feed on the acid-base balance of mink.

The acid-base balance in small carnivores (mink, Mustela vison) was examined during 6 feeding periods, when the same animals were given different feeds during a prolonged time. The feeds consisted of normal farm feed to which different amounts of sulphuric acid-preserved feed and feed silaged with organic acids were added (Tables I--II). When the pH of the feed was decreased to below 5.5, the acid-base balance of the animals was changed and metabolic acidosis occurred (Tables III--V, Fig. 1). On neutralization of the acid-preserved feed a normal acid-base balance could be maintained. However, the growth of the animals was reduced after prolonged feeding with silage as they lost weight during the following periods (Table vii).     

Contribution to our knowledge of the physiology and metabolism of endurance horses

The functional and metabolic processes of the endurance horse are discussed, based on personal experience and the scientific literature. Research on the energetic and physiological aspects of prolonged effort is reviewed, as regards the performance structure, described by Neumann, for human physiology.Experimental data from our previous surveys on endurance horses, competing at different levels, are also presented and discussed.The results on amino acid levels in blood, and related metabolic pathways, during endurance events, lead to speculation on the effects of the race distance on metabolic processes during long-lasting low-intensity exercise. In fact, the event distance has a significant influence on amino acid mobilization and their use as energy sources. In human athletes, the disappearance of some amino acids from blood circulation is linked to the onset of central fatigue. The effect could be similar in endurance horses; therefore, the correct intake of amino acids, and a proper feeding strategy, could improve performance.Data are also provided on dehydration and oxidative stress associated with endurance work.     

Acid-base disorders in milk-fed calves with chronic indigestion.

Acid-base disorders were investigated in 50 calves with chronic indigestion and metabolic acidosis. In the calves that were unable to stand up, the acidosis was significantly more severe than in the calves that could stand up. The anion gap and four different components of the base excess were calculated by the method described by Fencl. The anion gap was high in more than half of the calves, and it was significantly associated with the base excess due to unidentified anions. However, in seven of the calves, the excess of unidentified anions would not have been detected without the calculations, which made it possible to measure the effect of sodium, chloride, plasma protein and unidentified anions on the acid-base balance. Twenty-four of the calves had a combination of hyperchloraemic and high anion gap metabolic acidosis. Changes in sodium and plasma protein concentrations had a minor impact on the calves' acid-base status.     

The influence on breeding, production, and acid-base balance when mink are fed on acidified feed.

It has been shown, partly in an investigation in which female mink were subject to increasing quantities of acid in their feed, and partly in an investigation of experimental animals which were fed with various concentrations of acid-preserved fishsilage, that there is a marked risk for a change of the acid-base balance to a metabolic acidosis when pH in the feed comes lower than 5. These investigations are also considered to show that mink's reproductive ability and general welfare is considerably affected when fed with large quantities of acid-preserved fish feed over a longer period, possibly because of alterations in the acid base balance. It is possible to reduce or avoid metabolic acidosis in mink by neutralizing silage or feed.     

Characterization of acid-base disturbances and effects on calcium and phosphorus balances of dietary fixed ions in pregnant or lactating does

Effects of fixed cation-anion balance on acid-base status and calcium and phosphorus balances were examined. Pregnant and lactating goats were fed a diet of alfalfa hay, concentrate and minerals to vary the cation-anion balance [meq sodium (Na) + meq potassium (K)-meq chloride (Cl)]/100 g diet dry matter (DM) over the range found in ruminant feeds. Small but significant effects on ruminal pH, fermentation and dilution rate were observed. Metabolic acid-base status of pregnant and lactating goats was normal when (Na + K - Cl) balance was 40 to 50 meq/100 g DM. The other treatments drastically altered plasma electrolyte concentrations, causing metabolic acid-base disturbances and profound changes in calcium and phosphorus metabolism. Subclinical hypernatremic, hypochloremic metabolic alkalosis was induced by a dietary fixed cation excess (Na + K - Cl) of greater than 85 meq/100 g DM (typical of buffered, alfalfa diets) and caused hypocalciuria, diminished calcium and phosphorus absorption, and possibly diminished dietary calcium absorption and resorption of calcium from bone. Subclinical hyperchloremic, hyponatremic metabolic acidosis from a diminished dietary fixed cation-anion balance (Na + K - Cl) of less than 10 meq/100 g DM (typical of nonbuffered corn silage or grain diets) caused hypercalciuria, enhanced calcium and phosphorus absorption and apparently enhanced calcium resorption from bone. Apparent effects on absorption and resorption depended on calcium and phosphorus intakes. Alterations in goats performance were not demonstrable. Dietary excesses of fixed cations over anions (meq Na + K - Cl/100 g diet DM greater than 50) cause metabolic alkalosis in ruminants, whereas fixed anion excesses (meq Na + K - Cl/100 g diet DM less than 40) cause metabolic acidosis. Content of electrolytes in diets should be reported in all nutrition trials with ruminants for assessment of metabolic acid-base status.     

蛋氨酸在动物体内代谢途径与周转机制

蛋氨酸(Met)是动物机体的必需氨基酸,可作为合成蛋白质的底物,也是机体代谢重要的甲基和巯基供体,同时还参与多胺的形成。为此,Met的供应状况以及其在体内的代谢途径影响着机体的生长性能、生理活动,乃至于DNA和功能蛋白质的甲基化修饰,进而影响机体正常的生命活动。本文就Met的4种代谢通路及其相应的周转机制进行综述,以期为Met代谢机理研究和合理科学应用提供参考。     

Changes in the acid-base index of blood in dairy cows in relation to the seasonal composition of feed rations and phases of the reproductive cycle

The changes in the acid-base indices of the blood of dairy cows in different stages of reproduction cycle were studied in relation to the composition of feed ration in the autumn, winter, spring and summer feeding seasons. The cows were in the following stages of their reproduction cycle: Group I the fourth to sixth month of gravidity, II eighth to ninth month of gravidity, III one to two months after calving. The seasonal composition of feed ration was demonstrated to exert a significant influence on the acid-base balance of the blood of cows in the studied stages of reproduction. A considerable occurrence of metabolic acidoses with different levels of compensation was observed when the cows were given the autumn and winter feed rations. Subclinical acid-base disorders of different directions (metabolic and respiratory alkaloses, acidoses) frequently occurred in the green feeding season. The frequency of acid-base disorders as a result of incorrect nutrition was found to be the highest in highly pregnant cows (group II) and in those one to two months after parturition (group III), i. e. in the periods with a significant influence on the reproduction process. On the whole, the best situation as to the acid-base balance was found in cows in the fourth to sixth month of their gravidity, irrespective of the seasonal effect of feed ration.     

The seasonal fluctuation of plasma amino acids in aquarium-maintained bottlenose dolphins (Tursiops truncatus)

Although there has been extensive research on plasma amino acid profiles of mammals, there is currently a lack of information on seasonal differences in the concentrations of plasma amino acids specifically in cetaceans. The present study examined the response of the plasma amino acids to seasonal changes in the culture environment after controlling for the effect of sex and age. Significant seasonal changes in plasma carnosine (P=0.012), cystine (P=0.0014), isoleucine (P=0.0042), methionine (P=0.002), ornithine (P=0.0096), and taurine (P=0.032) were observed. These amino acids were mainly related to capacity for exercise, ammonia detoxification, thermoregulation, and osmoregulation. We proposed that optimizing plasma amino acids levels by supplementation of amino acids should be of considerable benefit for aquarium-maintained bottlenose dolphins. This study constitutes a first step towards improving our understanding of the metabolism of aquarium-maintained bottlenose dolphins. We also revealed that the ratio of tryptophan to large neutral amino acids significantly declined (P=0.0076), suggesting reduction in serotonin synthesis in winter and autumn. Although further studies are needed, this finding implied that bottlenose dolphins could produce behavioral changes seasonally by the alteration of serotonin activity. To better understand the metabolic machinery for amino acids that facilitate the adaptation of marine mammals to their environments, it is essential to continue monitoring of and further investigations into relationships between plasma amino acids and specific environmental factors.     

Subacute butyric acid burden in cattle. 2. Effect on the acid-base balance and the protein metabolism in young fattening bulls

Three weeks of butyric acid applications (0.5 g/kg and 1.0 g/kg body weight) caused strong dose-dependent strains on the acid-base balance in young fattening bulls aged 4 months. Disorders were primarily reflected in changed net values of acid-base excretion in urine. Activity of alkaline phosphatase was found to depend strongly and directly on these changes. Drastic variations were recorded also from nitrogen metabolism.     

支链氨基酸调控机体糖代谢的研究进展

支链氨基酸是体内最丰富的必需氨基酸,包括亮氨酸﹑异亮氨酸和缬氨酸。支链氨基酸具有促进蛋白质合成、提高机体免疫力和促进胚胎发育等生理功能。支链氨基酸在机体糖代谢调节中发挥着重要作用,其可以通过调控机体胰岛素的分泌﹑胰岛素的敏感性以及葡萄糖转运载体的表达和易位等方式调控糖代谢。本文对支链氨基酸在体内的代谢途径及其调控机体糖代谢的途径进行综述。     

Relevance of apolipoproteins in the development of fatty liver and fatty liver-related peripartum diseases in dairy cows

Most metabolic diseases in dairy cows occur during the peripartum period and are suggested to be derived from fatty liver initially developed during the nonlactating stage. Fatty liver is induced by hepatic uptake of nonesterified fatty acids that are released in excess by adipose tissues attributable to negative energy balance. The fatty accumulation leads to impairment of lipoprotein metabolism in the liver, and the impairment in turn influences other metabolic pathways in extrahepatic tissues such as the steroid hormone production by the corpus luteum. Detailed understanding of the impaired lipoprotein metabolism is crucial for elucidation of the mechanistic bases of the development of fatty liver and fatty liver-related peripartum diseases. This review summarizes results on evaluation of lipoprotein lipid and protein concentrations and enzyme activity in cows with fatty liver and those with ketosis, left displacement of the abomasum, milk fever, downer syndrome and retained placenta. Obtained data strongly suggest that decreases in serum concentrations of apolipoprotein B-100, apolipoprotein A-I and apolipoprotein C-III, a reduction in activity of lecithin:cholesterol acyltransferase and induction of haptoglobin and serum amyloid A are intimately related to the development of fatty liver and fatty liver-related diseases. Moreover, determination of the apolipoprotein concentrations and enzyme activity during the peripartum period is useful for early diagnoses of these diseases.     

Effect of dietary electrolyte balance on growth and acid-base status in swine

The effect of dietary electrolyte balance on pigs fed lysine- or tryptophan-adequate or tryptophan-deficient diets was investigated in four experiments using 8- to 12-wk-old pigs. Electrolyte balance, expressed as Na+K-Cl in meq/kg of diet, was varied by altering dietary levels of Na and Cl while holding all other minerals constant. In two experiments in which the basal diet contained a balance of 135 meq/kg, simple lysine or tryptophan deficiences caused depressed growth, feed intake and efficiency of feed utilization, but none of these responses was altered by dietary supplementation with NaHCO3. In one experiment in which the electrolyte balance of the basal diet was 61 meq/kg and in which both lysine and tryptophan were limiting. NaHCO3 supplementation significantly increased growth and feed intake. This did not occur if the diet was also supplemented with tryptophan. A final experiment was conducted to determine the response of pigs to a range of electrolyte balance (-85 to 341 meq/kg) in a practical corn-soy diet containing adequate levels of all amino acids. Growth and feed intake appeared to be maximal for balances of 0 to 341 meq/kg Na+K-Cl, but were decreased at -85 meq/kg (P less than .05). Acid-base balance was adversely affected at 0 meq/kg. The results suggest that the response of lysine-deficient pigs to sodium bicarbonate is dependent upon the electrolyte balance of the diet, and also is influenced by other dietary amino acids.     

Examination of mink (Mustela vison) fed a sulphuric acid preserved fish during lactation and growth period. I. A clinical-chemical examination

Addition of sulphuric acid preserved fish in great amounts as fur animal feed has a serious influence on the metabolism of the animals. The present experimental work shows that several clinical-chemical parameters are changed during feeding of acid preserved feed resulting in changes of the fluid-, electrolyte- and acid-base balance as well as in the immunological status. The changes are most probably due to changes also found in the organ functions. The present work together with earlier investigations by the authors has formed the scientific background for the use of acid preserved fish silage in mink during the last 10 years. This has made it possible to out-distance the competitors further, both with respect to fur quality and feeding costs.     

Metabolic acid-base disorders.

Acid-base homeostasis is an important determinant of many physiologic functions. Nowhere is understanding the mechanisms and significance of hydrogen ion (H+) imbalance more important than in critical care management, where patients are threatened with a physiochemical disorder that is often as complex as it is dangerous. Although there may be contentious issues yet unresolved concerning acid-base homeostasis, the incontrovertible fact is that the body at least seems to defend H+ balance as vigorously as it does oxygen transport or perfusion pressure. Equally, there seems to be an important and predictable relation between this balance and other physiochemical variables such as concentrations of other ionic species, carbon dioxide, and plasma proteins. The prudent clinician strives to understand whether or not and how acid-base imbalances are affecting his or her patient and what to do about it.     

奶牛分娩前后瘤胃代谢物变化规律及其代谢通路研究

本试验旨在阐明奶牛分娩前后瘤胃代谢物及其代谢通路的变化规律。选取10头体况和胎次相近的健康待产荷斯坦奶牛,分别于分娩前后晨饲前采集瘤胃液,采用UPLC-MS/MS代谢组学技术和MetaboAnanlyst 5.0中的通路分析方法研究奶牛分娩前后瘤胃发酵产物及其代谢通路的变化规律。结果表明,奶牛分娩后瘤胃中57种代谢物含量较分娩前发生了明显变化,其中34种代谢物含量显著降低,23种代谢物含量显著升高,9个代谢通路（牛磺酸和亚牛磺酸代谢、精氨酸和脯氨酸代谢、精氨酸的生物合成、D-谷氨酰胺和D-谷氨酸代谢、淀粉和蔗糖代谢、半乳糖代谢、丙氨酸、天冬氨酸和谷氨酸代谢、嘌呤代谢和维生素B₆代谢）发生了显著变化。本研究表明,奶牛在分娩前7~10 d与氨基酸、糖、核苷酸和维生素相关的瘤胃微生物菌群组成发生了应答性改变。     

Correction of metabolic acidosis in diarrheal calves by oral administration of electrolyte solutions with or without bicarbonate

Acid-base balance was evaluated in calves with experimentally induced viral diarrhea. When blood pH decreased to less than 7.200, calves were assigned to treatment groups and fed milk replacer, electrolyte solution without bicarbonate, or electrolyte solution containing bicarbonate. Calves in the electrolyte treatment groups had lower mortality (P less than 0.05), were better hydrated (P less than 0.05), and were less acidotic (P less than 0.05) than calves fed milk replacer. Bicarbonate-containing electrolyte solution restored acid-base balance (P less than 0.05) and corrected depression better (P less than 0.05) than electrolyte solution that did not contain bicarbonate. Both electrolyte solutions were equally good at correcting dehydration.     

基于LC-MS代谢组学的植物乳杆菌发酵黄芪的代谢产物分析

试验旨在利用色谱-质谱联用（liquid chromatograph-mass spectrometer,LC-MS）代谢组学技术分析植物乳杆菌发酵黄芪的代谢产物,并探索其互作发酵机制。分别采取植物乳杆菌发酵黄芪（FT组）和未发酵黄芪固态粉末（CT组）,经样本前处理、LC-MS分析、生物学信息分析等探寻差异代谢物并分析代谢通路。结果显示,总离子流图峰图重现性良好,发酵黄芪主要代谢物共鉴定出183种代谢成分,正离子和负离子模式样品间关系PCA图均能良好区分。火山图分析表明,FT和CT组间的代谢物变化具有差异性,正离子模式上调的1 416个代谢物富集到83个代谢途径;下调的935个代谢物富集到83个代谢途径;负离子模式上调的1 040个代谢物富集到52个代谢途径,下调的809个代谢物富集到45个代谢途径。发酵黄芪差异代谢产物酸类、脂类、酮类等氨基酸显著增加,烯类等氨基酸显著下调,其中上调代谢物15个,下调代谢物2个,关键代谢产物主要为α-硫酸二乙酯、2-甲基柠檬酸、3-异丙烯基-6-氧代庚酸等,涉及到丙酮酸代谢、丙酸代谢、半乳糖代谢等途径。本研究结果为发酵黄芪的代谢产物、发酵互作机制和临床应用提供理论依据。     

Effect of acute deficiency of dietary proline on proline balance in the rat small intestine and liver

Introduction Proline is widely found in all types of mammalian tissue, and accounts for about 20% of the amino acids that constitute collagen (A dams 1970). Proline is nutritionally nonessential but biologically it is an important amino acid and consequently mammalian organisms synthesize the required amounts of proline even in the absence of sufficient proline consumption via food. The metabolism of higher animals is unique, and amino acid metabolism differs from one tissue to the next. Some organs are capable of synthesizing nonessential amino acids for use throughout the body. For example, arginine is primarily synthesized in the kidney and then released and distributed throughout the body. Pyrroline-5-carboxylate reductase is the enzyme responsible for the final stage of proline synthesis, and its activity has been confirmed in many important organs and tissue such as the cartilage, liver, small intestine, kidney and thymus gland (H erzfeld et al. 1977; S mith and P hang 1978). However, the different levels of pyrroline-5-carboxylate reductase activity among these organs has led to the belief that different amounts of proline are synthesized in these organs. In order to ascertain biological responses to dietary proline deficiency, it is important to identify the organs that release and distribute proline throughout the body when insufficient proline is consumed through the diet, thus reducing the blood proline concentration. Few studies have investigated this issue, but when ascertaining biological responses to dietary proline deficiency, it is more important to elucidate the effect of dietary proline deficiency on the metabolism of proline and other amino acids that are closely related metabolically to proline, in proline synthesizing organs. One of the most effective ways to assess amino acid metabolism in a target tissue of higher animals is to measure the difference between the arterial and venous concentrations of amino acids. I shikawa (1974) measured arteriovenous differences in order to examine the release of proline from the kidney and small intestine of fasted rats and the uptake of proline by the liver. In a previous study, it was found that when the plasma proline concentration was reduced to the fasting level by the consumption of a proline-deficient diet, proline was released from the kidney (W atanabe et al. 1995, 1997). In the present study, to ensure the induction of dietary proline deficiency, a completely purified diet containing all amino acids except for proline was prepared and fed to rats under experimental conditions. To investigate the role of the small intestine and liver in supplying and ingesting proline when the uptake of proline through food is restricted, the release and uptake of amino acids in the small intestine and liver were assessed by measuring carotid artery–portal vein and portal–hepatic vein differences in proline in rats.