单胃动物消化道内源氨基酸排泄量的测定方法研究进展

氨基酸的利用受消化率的影响最大,消化吸收后的氨基酸仅有很小一部分不能为体内代谢利用。从实际应用的角度出发,经常把可消化氨基酸与可利用氨基酸看作等同的概念。目前普遍认同的是饲粮蛋白质和氨基酸的消化率测定应在回肠水平而不是粪水平。但由于回肠食糜蛋白中包含了相当数量的非日粮蛋白质(内源和微生物),M oughan等(1989)研究报道,代谢氨基酸及胃肠道内源氨基酸的损失占生长猪氨基酸维持需要量的绝大部分。D eLange等(1995)也研究报道,内源氮损失在畜禽维持氮需要中所占的比例最大。因此,准确量化回肠末端内源氨基酸流量的方法学问…     

畜禽基础氮代谢及无氮日粮配制研究进展

研究动物的基础氮代谢是测定蛋白质真消化率的关键步骤,是了解动物维持蛋白质需要的必要环节,准确测定动物的内源氮损失具有重要意义。本文对基础氮代谢、无氮日粮法及存在问题和影响无氮日粮配制的因素进行了综述。     

猪内源氮损失的调控

综述了猪内源氮损失、影响猪内源氮损失的因素及减少猪内源氮损失的措施，这有助于降低猪内源氮排出，提高氮的利用率，减轻养猪对环境的氮污染。     

大豆胰蛋白酶抑制因子降低小型猪外源性蛋白质的吸收和提高内源性蛋白质损失

本试验的目的是,研究胰蛋白酶抑制因子是否通过提高内源性和外源性蛋白质的损失降低蛋白质消化率,并在实验室中应用高精氨酸技术确定这些损失的数量。装有持久性回肠T—套管的猪,饲喂含高精氨酸标记的蛋白质试验日粮,日粮含有酪蛋白并提高胰蛋白酶抑制因子剂量(试验1),或进行热处理或粗制粉碎大豆(试验2),酪蛋白日粮组(425mmol氮,无胰蛋白酶抑制因子)猪回肠蛋白质内源性来源显著高于外源性来源(105对9mmol氮),添加分离的胰蛋白酶抑制因子(3000mg)显著提高回肠内源性和外源性蛋白质(73对9mmol氮)。在单一试验日粮中,饲喂粗制而未热处理的大豆显著提高内源性蛋白质(217±42→263±47mmol)和外源性蛋白质(16±3→48±14mmol)。如果连续饲喂1周粗制大豆日粮,可导致内源性蛋白质损失从221±26显著提高到432±85mmol。我们的结果是,摄入含有胰蛋白酶抑制因子的饲料,通过氨基酸内源性分泌的 损失影响氮平衡,较通过日粮氨基酸损失大。     

相比于完整酪蛋白,酪蛋白水解物不能提高生长猪回肠内源性蛋白流量

日粮中氮的存在形式(游离肽或完整蛋白)可能会影响猪回肠末端中内源性氨基酸的含量,人们认为日粮中蛋白水解后可增加内源性氨基酸。本研究旨在对比日粮中同一蛋白源消化所得的游离肽对回肠内源氮流量和回肠内源性氨基酸流量(ENFL,EAAFL)的影响。选用六头装有后瓣膜T性盲肠套管(PVTC)的猪(平均体重34千克)。半纯合日粮含有同样的15N标记的酪蛋白(C)或水解酪蛋白(HC),每六天饲喂一次标记过的日粮,其余五天饲喂相应无标记日粮。采食后4至10小时收集食糜。利用日粮中标记物TiO 2,以及C和HC中稀释后的同位素含量来计算EAAFL和ENFL值。HC组和C组回肠EAAFL和ENFL(在饲喂HC和C日粮时干物质摄入的平均流量分别是1828和1912μg/g,n=5)两者无显著差异(P0.05)。经过离心和超滤后的HC食糜可作为标记性再循环回到肠道的内源性蛋白的指示物。经过对示踪剂的回收,约有20%的回肠内源性蛋白(日粮HC,超滤后食糜)是15N标记的。与完整的酪蛋白相比,酪蛋白水解物应用对回肠内源蛋白流量没有影响。没有直接证据证明酪蛋白水解物日粮会增加回肠内源性蛋白的损失。     

家兔蛋白质和氨基酸营养的新概念和目标

在欧洲，减少矿物质污染和禁用抗生素作为生长促进剂的新法规已引起氮供应目标的变化。作者综述了家兔氮营养的现状，蛋白质和氨基酸对健康的作用，以及基于未来营养需要的真回肠消化率（TID）蛋白源的新的氮价值。微生物生长的主要氮源是氨、尿素和来自内源及日粮的蛋白质，肥育期氮过量进入盲肠促使栖居病原微生物生长而增加了家兔的死亡率。作者还讨论了减少回肠氮流量的饲养技巧，日粮蛋白水平过低也可能对生产性能和死亡率有负面影响。为了配合平衡的低蛋白日粮，综述了14种原料的回肠和粪氨基酸消化率。同时讨论了氨基酸消化率的不同单位。     

家禽内源氨基酸损失测定的可重复性与无氮饲粮的配制

准确评估内源氨基酸损失是建立家禽标准回肠可消化氨基酸或回肠真可消化氨基酸模式的基础。在现有方法中,无氮饲粮法(NFD)测定家禽基础内源氨基酸损失的一致性或可重复性最高。先前很多研究所采用的无氮饲粮配方不同,为减小结果变异,无氮饲粮的配制需要建立统一标准。此外,家禽内源氨基酸损失测定还需考虑品种和日龄等因素以及饲粮特异性内源氨基酸损失。本文讨论了家禽内源氨基酸损失测定的可重复性问题,并推荐了标准无氮饲粮配方。     

不同淀粉源对獭兔内源氮和内源能损失的影响北大核心CSCD

本试验旨在研究不同淀粉源对獭兔內源氮和内源能损失的影响。选用1.5岁左右健康的獭兔30只,随机分成3组,每组10只,公母各占1/2。3组獭兔分别饲喂玉米淀粉型、马铃薯淀粉型和木薯淀粉型无氮饲粮。预试期和正试期各7 d。结果显示:内源氮损失方面,各组獭兔的代谢粪氮(MFN)和内源尿氮(EUN)差异不显著(P>0.05);总体上看,木薯淀粉组内源氮损失最高,马铃薯淀粉组最低,玉米淀粉组居中;内源能损失方面,各组獭兔的代谢粪能(Fm E)和内源尿能(Ue E)差异不显著(P>0.05);总体上看,木薯淀粉组内源能损失最高,马铃薯淀粉组最低,玉米淀粉组居中。由此得出,虽然不同淀粉源对獭兔MFN、EUN、Fm E和Ue E均无显著影响,但总体看,木薯淀粉组獭兔的内源氮和内源能损失要高于玉米淀粉组和马铃薯淀粉组。     

不同淀粉源对獭兔内源氮和内源能损失的影响

本试验旨在研究不同淀粉源对獭兔內源氮和内源能损失的影响。选用1.5岁左右健康的獭兔30只,随机分成3组,每组10只,公母各占1/2。3组獭兔分别饲喂玉米淀粉型、马铃薯淀粉型和木薯淀粉型无氮饲粮。预试期和正试期各7 d。结果显示:内源氮损失方面,各组獭兔的代谢粪氮(MFN)和内源尿氮(EUN)差异不显著(P0.05);总体上看,木薯淀粉组内源氮损失最高,马铃薯淀粉组最低,玉米淀粉组居中;内源能损失方面,各组獭兔的代谢粪能(Fm E)和内源尿能(Ue E)差异不显著(P0.05);总体上看,木薯淀粉组内源能损失最高,马铃薯淀粉组最低,玉米淀粉组居中。由此得出,虽然不同淀粉源对獭兔MFN、EUN、Fm E和Ue E均无显著影响,但总体看,木薯淀粉组獭兔的内源氮和内源能损失要高于玉米淀粉组和马铃薯淀粉组。     

大豆胰蛋白酶抑制因子降低小型猪外源性蛋白质的吸收和提高内源性蛋白质…

本试验的目的是，研究胰蛋白酶抑制因子是否通过提高内源性和外源性蛋白质的损失降低蛋白质消失率，并在实验室中应用高精氨酸技术确定这些损失的数量。装有持久性回肠Ｔ一套管的猪，饲喂含精氨酸标记的蛋白质试验日粮，日粮含有酷蛋白并提高胰蛋白酶抑制因子剂量（试验１），或进行热处理或粗制粉碎大豆（试验２）酷蛋白粮组（４２５ｍｍｏｌ氮，无胰蛋白酶抑制因子）猪回肠蛋白质内源性来源显著高于外源性来源（１０５对９ｍｍｏｌ     

仔猪精氨酸的内源合成及其影响因素

由于精氨酸及其代谢产物具有广泛生物学作用,使得近年来研究者们在生理、生化和营养等方面对其作了大量的研究。母乳严重缺乏精氨酸,仔猪精氨酸内源合成对精氨酸的平衡起了重要作用,使得哺乳仔猪精氨酸的内源合成成为精氨酸营养的研究核心。通过对精氨酸内源合成路径和场所的了解,研究者们进一步研究了精氨酸内源合成的影响因素,主要有仔猪日龄、日粮中精氨酸的水平、乳酸盐和皮质醇的浓度等。本文就仔猪精氨酸内源合成的途径和场所、内源合成的量、影响因素以及精氨酸的需要量等进行了综述,重点阐述了精氨酸内源合成的影响因素。     

Alleviation of body weight loss by dietary methionine is independent of insulin‐like growth factor‐I in protein‐starved young chickens

It is well known that in protein‐starved chickens, small amounts of amino acid supplement, especially methionine, reduces nitrogen excretion and thereby improves nitrogen balance. On the other hand, excess intake of methionine causes growth depression and the growth‐depressive effect of excess methionine can be alleviated by consumption of dietary glycine. Insulin‐like growth factor‐I (IGF‐I) is one of various growth‐promoting factors relating to the efficiency of animal production and is known to be very sensitive to changes in nutritional status. In the present study, the interactive effect of glycine on nitrogen sparing effect of methionine in protein‐starved chickens was examined. In addition, the relation of IGF‐I and its specific binding protein to the nitrogen sparing effect of supplemented methionine was also investigated. Two‐days refeeding of methionine supplemented to protein‐free diet could promptly alleviate body weight loss in protein‐starved chickens, and the alleviation of body weight loss by methionine was not improved by glycine supplements. Moreover, such acute alleviation of body weight loss by dietary methionine was independent of the change in plasma IGF‐I concentration.     

单胃动物内源氨基酸损失的测定方法及影响因素研究进展

氨基酸消化率是评定饲料蛋白质生物学效价的重要指标。对内源氨基酸损失进行准确测定可获得精准的氨基酸消化率,不仅可以节约日粮蛋白资源,降低饲料成本,还可减少因氮排放造成的环境污染。目前,内源氨基酸损失测定的方法主要包括无氮日粮法、绝食法、差量法、酶解蛋白日粮法、回归法、高精氨酸法和同位素法等。内源氨基酸损失又与动物、饲养环境、日粮组成(日粮蛋白、纤维、抗营养因子)及测定方法等有关。本文综述了内源氨基酸损失的测定方法及影响因素。     

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。     

Advances in low-protein diets for swine

Recent years have witnessed the great advantages of reducing dietary crude protein(CP) with free amino acids(AA)supplementation for sustainable swine industry, including saving protein ingredients, reducing nitrogen excretion, feed costs and the risk of gut disorders without impairing growth performance compared to traditional diets. However, a tendency toward increased fatness is a matter of concern when pigs are fed low-protein(LP) diets. In response, the use of the net energy system and balanced AA for formulation of LP diets has been proposed as a solution. Moreover, the extent to which dietary CP can be reduced is complicated. Meanwhile, the requirements for the first five limiting AA(lysine, threonine, sulfur-containing AA, tryptophan, and valine) that growing-finishing pigs fed LP diets were higher than pigs fed traditional diets, because the need for nitrogen for endogenous synthesis of non-essential AA to support protein synthesis may be increased when dietary CP is lowered. Overall, to address these concerns and give a better understanding of this nutritional strategy, this paper reviews recent advances in the study of LP diets for swine and provides some insights into future research directions.     

Progress in ileal endogenous amino acid flow research in poultry

The progress in our understanding of the endogenous protein concept over the past century is reviewed. Nondietary proteins found in the digesta at the terminal ileum of poultry, known as endogenous protein loss, are comprised of digestive secretions, mucus and sloughed gut epithelial cells. The measurement of this loss is of fundamental importance because it is an indicator of gut metabolism and is essential to adjust apparent estimates of ileal amino acid digestibility. The ileal endogenous amino acid losses comprise of two components, namely basal and specific losses. The basal losses are fixed and associated with feed dry matter intake, whereas the specific losses are variable and induced by the presence of dietary components such as fibre and anti-nutrients. Currently there is no methodology available to directly measure the specific endogenous losses and these losses are calculated by determining the basal and total(basal plus specific) losses and, then subtracting the basal losses from total losses.The seminal features, specific applications and shortcomings of available methodologies are briefly outlined as well as the practical challenges faced in using the published endogenous amino acid loss values for true digestibility corrections. The relevance of taurine as a component of endogenous protein flow in poultry is identified for the first time.     

Pathophysiology of nematodiasis in cattle

Recent detailed studies of the physiologic changes occurring in cattle infected with some of the common gastrointestinal nematodes have shown that the weight loss and reduced carcass values resulting from these infections are a consequence of major alterations in host metabolism. Dramatic changes in protein metabolism were consistently found to involve decreased muscle synthesis and increased urinary nitrogen excretion. Because of the well-recognized loss of plasma proteins into the gut lumen and cellular damage at the mucosa occurring during nematode infections of the abomasum and duodenum, it has been assumed that protein was being lost in feces or not absorbed; however, this loss has proved not to be as significant as postabsorptive protein catabolism in these infections. Only when the colon and cecum are involved in protein-losing infections is the loss of protein into the feces significant. The mechanisms by which gastrointestinal nematode infections result in such altered host metabolic states are not known, but suggestions have been made that parasites directly or indirectly alter gut hormone levels. Gut hormone changes may also be responsible for diarrhea and anorexia. Another mechanism of altering metabolism has been proposed for chronic parasitisms that stimulate macrophages. Macrophages produce a peptide called cachectin, and cachectin is thought to mediate protein and lipid catabolism. This mechanism obviously could be contributing to weight loss and anorexia whenever nematodes cause sufficient macrophage activation, including during lungworm infections, which do not have enteric involvement.     

饲粮蛋白质水平对冬毛生长期水貂生长性能、血清生化指标及毛皮质量的影响

本文旨在探讨饲粮蛋白质水平对水貂生长性能、营养物质消化吸收、毛皮品质和血清生化指标的影响.随机选取日龄体重相近的70只健康公水貂平均分至5组,饲喂5个蛋白质水平的饲粮(32%、28%、24%、20%和16%),每千克干物质中含蛋白质分别为326.4、284.7、249.3、203.9和172.8 g.试验组编号分别为P...     

肠道健康标准和影响家禽肠道健康的因素分析及其防控方案

肠道作为整个机体主要的消化器官和体内最大的免疫器官,在家禽的生长发育和繁殖生产中起着至关重要的作用。肠道健康标准可为生产中及时监测并准确判断肠道的健康状况提供依据,了解肠道屏障的损伤机制有助于制定相应的防控策略。在实际生产中影响家禽肠道健康的因素众多,主要包括:致病性病毒、细菌、真菌和寄生虫等感染;饲料卫生、饲料霉菌及其毒素、日粮抗原、应激因素、禽舍环境卫生等。文章重点介绍了畜禽肠道健康的五大标准和评价肠道是否健康的相关生物标记物,阐述了影响家禽肠道健康的因素,肠道屏障损伤的机制,并针对不同因素导致的肠道健康问题阐明了不同的防控方案。     

The relevance of glycine and serine in poultry nutrition: a review

ABSTRACT

1. Dietary glycine equivalents (Gly_equi) for glycine and serine represent the first-limiting non-essential amino acid in poultry diets. Targeted adjustment of essential amino acids and Gly_equi in diets can considerably decrease crude protein (CP) in poultry diets below the limit of CP reduction when only essential amino acids are adjusted.

2. The level to which CP can be reduced in diets adequate in Gly_equi depends on the objective; which includes reducing dietary CP without affecting performance and increasing nitrogen utilisation efficiency. Dietary CP can be reduced to ~15–16% in diets for up to 21 d old broiler chicken without affecting growth performance compared to responses to diets with currently common CP concentrations by considering Gly_equi in the diet formulation. Dietary CP can be further reduced to maximise nitrogen utilisation efficiency; however, this leads to reduced growth performance.

3. The dietary Gly_equi requirement of poultry varies depending on other dietary constituents. In broiler chickens up to 21 days of age, the dietary Gly_equi requirement is estimated to be between 11 and 20 g/kg. This estimate is influenced by the concentrations of Cys and the endogenous Gly_equi precursors, threonine and choline. Urinary nitrogen excretion seems to be a major determinant of the response to dietary Gly_equi, because it is needed for uric acid formation.

4. The variable requirement for dietary Gly_equi means that its static recommendation in poultry diets would lead to high safety margins in Gly_equi supply or the risk of Gly_equi deficiency. Variable recommendations for dietary Gly_equi concentrations would help to supply birds based on their specific requirements and could reduce nitrogen emissions originating from poultry farming.