小肽对动物免疫功能的影响

长期以来,人们一直认为动物采食的日粮蛋白质在消化道内降解成小肽和游离氨基酸,游离氨基酸可以被动物直接吸收利用,而小肽只有进一步降解成游离氨基酸才能被利用,后来发现,蛋白质降解产生的小肽也能被动物直接吸收。从此,小肽在动物生产中的应用开始了广泛的研究。众多研究表明,小肽具有促进氨基酸的吸收,     

小肽营养的研究进展

小肽是动物降解蛋白质为氨基酸过程的中间产物,是动物的重要营养物质,是除氨基酸之外的蛋白质营养吸收代谢的重要方式之一。在氨基酸的消化、吸收和代谢中,小肽起着非常重要的作用。对小肽的释放、吸收机制、营养作用与生理功能进行了综述。     

小肽营养研究进展

经典营养学认为 ,动物采食的日粮蛋白质在消化道内经蛋白酶和肽酶的作用降解为小肽和游离氨基酸 ,游离氨基酸可以被动物直接吸收利用 ,而小肽只有进一步降解成游离氨基酸才能被利用 ,理想蛋白质、可利用氨基酸等系列蛋白质营养理论就是在此基础上建立起来的。后来发现 ,动物对饲料中各种氨基酸的利用程度并不完全受单一限制性氨基酸水平的影响 ,也不完全遵循“木桶理论” ,而且即使喂给动物按理想氨基酸模型配制的纯合日粮或低蛋白平衡日粮 ,也不能获得最佳生产成绩。因而 ,有些学者提出了完整蛋白质或其降解产生的小肽也能被动物直接吸收的…     

动物源小肽在生长猪日粮中的应用

传统动物营养学认为,动物采食的日粮蛋白质在消化道内经蛋白酶和肽酶的作用降解为小肽和游离氨基酸,游离氨基酸可以被动物直接吸收利用,而小肽只有进一步降解成游离氨基酸才能被利用。理想蛋白质和可利用氨基酸等蛋白质营养理论就是在此基础上建立起来的。后来研究发现．动物饲料中各种氨基酸的利用程度并不完全受单一限制性氨基酸水平的影响,     

小肽吸收机制及在动物生产中的应用

传统的经典蛋白质营养理论即氨基酸营养理论认为,动物采食的日粮蛋白质在消化道内经蛋白酶和肽酶作用降解为小肽和游离氨基酸,游离氨基酸可被动物直接利用,而小肽只有进一步降解为游离氨基酸才能被利用。但在后来的一些研究中发现,用纯合日粮或低蛋白质平衡氨基酸日粮饲喂动物,并不能达到最佳生产性能。Agao等(1953)首先观察到肠道能完整地吸收转运双甘肽。Neway等(1960)的研究为小肽能被完整吸收提供了证据。Hara等(1984)在小肠黏膜上发现了小肽载体。Garder(1984)研究也表明,大量小肽能直接被吸收,进入体循环。Webba(1989)研究表明,蛋白…     

乐能大豆肽在仔猪饲料中的应用

蛋白质营养一直是动物营养的重要组成部分,传统营养学理论认为,蛋白质在动物体内完全降解为氨基酸后再被吸收。随着科学研究的不断深入,人们逐渐认识到,蛋白质在动物体内一部分完全降解为氨基酸后被吸收,而另一部分则以小肽(主要是二肽、三肽)的形式被完整吸收。众多的研究表明     

肠道小肽吸收利用机制及其营养功能

小肽是动物降解蛋白质过程中的中间产物,是由2个或2个以上的氨基酸以肽键相连的化合物,其吸收在总饲粮蛋白质的吸收中有重要作用。本文综述肠道对小肽的吸收利用及其调控机制,肠道小肽感应与胃肠激素分泌和摄食调控,肠道小肽利用对肠道健康的调控,以及小肽在动物营养中的应用。     

小肽营养及其在水产养殖中的应用进展

长期以来．人们一直认为动物采食的日粮蛋白质在消化道内降解成小肽和游离氨基酸．游离氨基酸可以被动物直接吸收利用；而小肽只有进一步降解成游离氨基酸才能被利用。后来发现，蛋白质降解产生的小肽也能被动物直接吸收。从此．小肽在动物营养中的应用开始了广泛的研究。水产养殖的研究表明．添加适量的小肽可促进鱼类的生长，增强水产动物的免疫力和提高成活率、矿物元素利用率、饲料转化率。本文针对小肽的吸收与代谢机制、影响小肽吸收和释放的因素以及小肽在水产养殖中的应用等方面做一论述。     

小肽在反刍动物营养中的应用

小肽是动物降解蛋白质过程中产生的中间产物,蛋白质在动物消化道内降解成游离氨基酸和小肽后被吸收。近年来,对寡肽特别是小肽在反刍动物蛋白质营养中的作用有了越来越多的研究。为了全面了解小肽在反刍动物营养中的应用情况。论文综述了小肽应用于反刍动物日粮中对反刍动物的生产性能、物质代谢及瘤胃发酵的作用效果,以期为小肽在反刍动物营养中的研究和应用提供参考。     

小肽的功能及其在家禽生产中的应用

小肽是动物降解蛋白质为氨基酸过程中的中间产物,是动物的重要营养物质。它能在动物胃肠内被完整的吸收,这被认为是一种重要的生理现象,完善了传统蛋白质代谢理论。文中就小肽的分类和吸收特点、小肽的功能、小肽在家禽养殖中的应用效果及其应用前景作了简要综述。     

反刍动物小肽吸收与利用的研究进展

蛋白质在动物消化道内降解成游离氨基酸和肽类后被吸收。试验表明,反刍动物以肽吸收为主要形式。这一点与单胃动物以氨基酸吸收为主不同,原因是反刍动物存在肽的非肠系膜吸收系统。近年来,对寡肽(Oligo-Peptide,OP)特别是小肽(Small—Peptide,SP)在反刍动物蛋白质营养中的作用有了越来越多的研究。本文回顾了国内外的研究进展情况。     

Peptide absorption: a review of current concepts and future perspectives.

Absorption of di- and tripeptides from the gastrointestinal tract is accepted as being an important biological phenomenon. The extent to which peptides are absorbed and the nutritional and metabolic significance of peptide absorption remain unclear. Evidence is strong for the existence of multiple peptide transport systems, including one type that is electrogenic in nature and that requires a protonmotive force and cotransports two H+ for every peptide transported. The rate of absorption of peptides can be responsive to level of dietary intake and level of dietary protein. Peptide absorption seems to be an important physiological process in ruminants, and this process may account for a large portion of absorbed amino acids. An important new observation is that the nonmesenteric portion of the portal-drained viscera of the ruminant is a major site of peptide absorption. These new observations may result in a reshaping of the currently accepted theory concerning protein utilization by ruminants.     

动物的肽吸收机制及组织利用

已有的研究证实,小肽的消化道吸收机制不同于氨基酸。已发现的吸收机制包括渗透扩散、中间载体转运、通道穿透吸收3种方式。其中,小肽的中间载体转运吸收有2种类型:(1)依赖跨膜的H 浓度梯度,H /肽共转运子在向吸收细胞内转运分子肽的同时伴随着两个H 的吸收,而跨膜的H 浓度梯度则是依靠耗能的Na /H 交换子来维持,H /肽共转运子和Na /H 交换子在功能上是独立的;(2)肽中间载体转运依赖跨膜的阳离子浓度梯度,而二价阳离子的促吸收作用高于一价阳离子。已知谷胱甘肽是通过第二种转运机制转运的。瘤胃和瓣胃具有很强的小肽吸收能力,可能是反刍动物肽吸收的主要部位,但有关研究的结果差异较大,与动静脉差法的测定误差较大有关。对于体组织肽利用的了解不多,已有的研究表明体组织可以利用小肽,其过程是组织吸收的肽在组织细胞内降解为氨基酸,而后用于蛋白质的合成和分解代谢。     

Intestinal absorption of protein hydrolysis products: a review

Many experimental techniques have allowed researchers to probe the fate of hydrolysis products from proteins in the small intestine. An overview of amino acid and peptide absorption from the small intestine is presented with attention given to historical perspectives that have led to current concepts. Speculation about nutritional significance of these processes is offered. Species differences exist in site of amino acid absorption. Numerous mechanisms are available for the transport of amino acids, including Na(+)-dependent carriers (energy-requiring), Na(+)-independent carriers and diffusion. The relative contribution each transport system makes to absorption is dependent on substrate concentration. Individual amino acids are not absorbed with equal efficiency; methionine usually is absorbed in the greatest proportion. There are interactions among amino acids for transports by specific transport systems. Small peptides (mostly di- and tripeptides) are absorbed from the small intestine more rapidly than are free amino acids; peptides are transported by systems independent of those responsible for transporting free amino acids. Evidence exists that the active transport of these peptides is via a proton gradient. Although the concept that peptides are absorbed intact into the circulation is not universally accepted, evidence supporting the possibility of tissue utilization of these small peptides is accumulating.     

动物的肽营养研究进展

蛋白质在动物消化道内经过各种消化酶的作用 ,降解成为游离氨基酸和肽。自 2 0世纪 6 0年代起人们逐渐认识到除了游离氨基酸 ,肽尤其是小肽也能够被动物直接吸收利用。肽除了对动物的营养作用外 ,某些有生理活性的肽直接被动物吸收利用后 ,还具有阿片肽活性、免疫调节、抗高血压、抗凝血、促进DNA合成等作用 ;影响肽吸收转运的因素主要有日粮的营养水平、蛋白质品质、动物采食量、肽分子结构等。本文就肽的吸收机制、对动物的营养和生理作用及影响其吸收的因素作一综述。     

小肽营养在养殖业中的应用研究进展

蛋白质在动物消化道内经过各种消化酶的作用,降解成为游离氨基酸和肽.自20世纪60年代起人们逐渐认识到除了游离氨基酸,小肽也能够被动物直接吸收利用.除了对动物的营养作用外,某些有生理活性的肽直接被动物吸收利用后,还具有阿片肽活性、免疫调节、抗高血压、抗凝血、促进DNA合成等作用.文章综述了小肽的营养与生理作用机制及其在现代养殖业中的应用研究进展.     

Metabolism of microbial nitrogen in ruminants with special reference to nucleic acids

Characteristically the metabolism of microbial nitrogen (N) compounds in ruminants involves the degradation of dietary N and synthesis of microbial protein (MP), compounds including a small amount of peptides and free amino acids, which may account for 75–85% of total N and the remainder are nucleic acids (NA: DNA and RNA). Generally rumen microbes contain 10–25% NA‐N of the total N while 70–80% is in the form of RNA. This paper describes the degradation and synthesis of NA in the rumen and their fate in the lower digestive tracts. Their physiological and nutritional significance in different types of ruminant animals is also discussed. The research works on NA metabolism in ruminants has been mainly on metabolism of purines after rumen microbial digestion and absorption in the lower gut. Subsequently, the fate of absorbed purines has been intensively investigated to assess the extent of MP synthesis in the rumen. The method for predicting ruminal synthesized MP and subsequently digested MP has been proposed using urinary purine derivative (PD) excretion in sheep and cattle fed on ordinary feed. The latter approach has now been adopted for calculation of protein supply in some feeding standards, although there are still difficulties in predicting representative samples of rumen microbes, and also uncertainties in variations of non‐renal and endogenous purine losses.     

反刍动物瘤胃上皮的结构特点

反刍动物的胃是复胃,与单胃动物的胃不同。反刍动物主要以瘤胃中发酵产生的短链脂肪酸（SCFA）作为机体的能量物质,而绝大部分的SCFA又通过瘤胃上皮直接吸收,为宿主供能。因此,深入了解瘤胃上皮结构特点有助于对其吸收功能进行深入的研究。笔者主要对瘤胃上皮的解剖学特点、细胞学特点及超微结构进行了综述。     

Ruminant Nutrition Symposium: Role of fermentation acid absorption in the regulation of ruminal pH

Highly fermentable diets are rapidly converted to organic acids [i.e., short-chain fatty acids (SCFA) and lactic acid] within the rumen. The resulting release of protons can constitute a challenge to the ruminal ecosystem and animal health. Health disturbances, resulting from acidogenic diets, are classified as subacute and acute acidosis based on the degree of ruminal pH depression. Although increased acid production is a nutritionally desired effect of increased concentrate feeding, the accumulation of protons in the rumen is not. Consequently, mechanisms of proton removal and their quantitative importance are of major interest. Saliva buffers (i.e., bicarbonate, phosphate) have long been identified as important mechanisms for ruminal proton removal. An even larger proportion of protons appears to be removed from the rumen by SCFA absorption across the ruminal epithelium, making efficiency of SCFA absorption a key determinant for the individual susceptibility to subacute ruminal acidosis. Proceeding initially from a model of exclusively diffusional absorption of fermentation acids, several protein-dependent mechanisms have been discovered over the last 2 decades. Although the molecular identity of these proteins is mostly uncertain, apical acetate absorption is mediated, to a major degree, via acetate-bicarbonate exchange in addition to another nitrate-sensitive, bicarbonate-independent transport mechanism and lipophilic diffusion. Propionate and butyrate also show partially bicarbonate-dependent transport modes. Basolateral efflux of SCFA and their metabolites has to be mediated primarily by proteins and probably involves the monocarboxylate transporter (MCT1) and anion channels. Although the ruminal epithelium removes a large fraction of protons from the rumen, it also recycles protons to the rumen via apical sodium-proton exchanger, NHE. The latter is stimulated by ruminal SCFA absorption and salivary Na(+) secretion and protects epithelial integrity. Finally, SCFA absorption also accelerates urea transport into the rumen, which via ammonium recycling, may remove protons from rumen to the blood. Ammonium absorption into the blood is also stimulated by luminal SCFA. It is suggested that the interacting transport processes for SCFA, urea, and ammonia represent evolutionary adaptations of ruminants to actively coordinate energy fermentation, protein assimilation, and pH regulation in the rumen.     

Identification of T-helper and linear B epitope in the hypervariable region of nucleocapsid protein of PPRV and its use in the development of specific antibodies to detect viral antigen

Peste des petits ruminants is a highly contagious viral disease of small ruminants making its diagnosis difficult from the similar symptoms of Rinderpest. Computer based prediction algorithms was applied to identify antigenic determinants on the nucleocapsid (N) protein of PPRV. Specificity and antigenicity of each peptide was evaluated by solid phase ELISA. Six specific peptide sequences were evaluated in multiple antigenic peptide (MAP) form and immune response was evaluated by supplementing universal T-helper epitope human IL-1beta peptide (VQGEESNDK, amino acids 163-171). Out of the six peptides 19mer sequence corresponding to 454-472 region of N protein of PPRV was found to be highly immunogenic and specific to PPRV. Evaluation of overlapping peptides differing in length for this 452-472 region, showed minimum length of 14 amino acid residues were required for the stable affinity binding of antigen-antibody. The results of immunization and indirect ELISA indicated the presence of T-helper epitope at the N-terminal end and linear B epitope at the C-terminal region of 454-472 19mer of nucleocapsid peptide of PPRV-nucleocapsid protein. The antipeptide antibodies developed against this region showed specificity to PPRV antigen differentiating it from RPV when used in indirect ELISA and western blot analysis.