反刍动物瘤胃氮代谢及其与瘤胃微生物相关性的研究进展

通过饲料养分调控瘤胃氮代谢是提高反刍动物氮利用效率的一种有效方式,其中能量和蛋白质对瘤胃氮代谢的影响尤为显著。能量和蛋白质通过调控瘤胃中的微生物进而影响瘤胃氮代谢过程,但两者对瘤胃中不同微生物的影响程度存在差异。本文综述了瘤胃中的氮降解过程、尿素氮循环、能氮平衡对瘤胃氮代谢的调控以及能量和蛋白质与瘤胃微生物之间的关系,为提高反刍动物氮利用效率和减少反刍动物氮排放量的研究提供科学依据。     

青粗饲料蛋白质及有机物瘤胃降解规律的研究

青粗饲料蛋白质及有机物瘤胃降解规律的研究颜品勋，冯仰廉，杨雅芳，莫放（中国农业大学动物科技学院北京１０００９４）前言进入反刍动物的小肠蛋白质包括饲料非降解蛋白质和瘤胃微生物蛋白质，而微生物蛋白质的合成又须由饲料降解蛋白质提供氮源，饲料蛋白质的降解率是...     

瘤胃微生物蛋白质产量的调控

反刍家畜瘤胃内栖居着大量微生物 ,其厌氧发酵合成的微生物蛋白可以为动物提供蛋白质需要量的 40 %～ 60 % (Church,1988)。小肠可利用的蛋白主要来自于微生物蛋白 (Orskov and Fraser,19 73) ,因此了解影响瘤胃微生物产量的调控因素对于研究反刍动物的营养调控技术有重要的意义。1　营养调控能量、蛋白质、进食水平、青贮饲料等都是影响瘤胃微生物蛋白质产量的营养因素 (韩兴泰 ,1993;袁森泉 ,1998;陈友慷 ,1991)。目前的研究主要集中于肽、氨基酸、维生素、微量元素、矿物质等方面。1.1　维生素反刍动物自身可以合成 B族维生素 ,能够满…     

饲料蛋白质在反刍动物瘤胃的降解及其影响因素

由于瘤胃细菌和原虫的作用,反刍动物利用蛋白质明显不同于单胃动物。饲料蛋白质进入瘤胃后,一部分被微生物降解为非蛋白氮,与饲料中原有的以及唾液中的非蛋白氮最终一起转变为氨。瘤胃微生物利用发酵生成的挥发性脂肪酸等作为碳架,并利用瘤胃发酵释放的能量(ATP)将氨合成微生物蛋白。微生物蛋白连同饲料蛋白质中的未降解部分(过瘤胃蛋白质),随着食糜流动进入真胃和小肠,被动物分泌的消化液(酶)分解为氨基酸,为动物体吸收和利用。大量研究表明,优质饲料蛋白质经过保护后,就能够满足高产反刍动物对过瘤胃蛋白质的需要,提高优质植物性蛋白质利用效率,动物的氮沉积及生产性能得到明显改善,同时根据瘤胃能氮平衡理论为在日粮中利用更多的非蛋白氮提供了可能。了解饲料蛋白质在反刍动物瘤胃的降解及其影响因素,可为制定过瘤胃蛋白质、氨基酸的技术措施提供依据。     

控释尿素对藏羊瘤胃氨氮和微生物蛋白质的影响

作者旨在探讨控释尿素对藏羊瘤胃氨氮和微生物蛋白质合成的影响。试验选4只2岁藏羊，安装永久性瘤胃瘘管，分期定量饲喂不同粗蛋白质日粮：含尿素日粮（粗蛋白质含量为10.79%）、无尿素日粮（粗蛋白质含量为10.75%）、控释尿素日粮（粗蛋白质含量为10.73%）。结果表明，含尿素日粮瘤胃pH和氨氮浓度在一天中变化较快，而无尿素日粮和控释尿素日粮变化较为平缓，控释尿素日粮微生物蛋白质合成量虽然变化幅度较大，但能量与氨氮释放同步，微生物蛋白质合成量较大，充分把食用氮转化为微生物蛋白质。控释尿素日粮与含尿素日粮、无尿素日粮存在极显著差异（P<0.01），且控释尿素在瘤胃pH、氨氮浓度和微生物蛋白质含量方面均优于含尿素日粮和无尿素日粮，从而表明采用控释尿素日粮对藏羊补饲具有良好的效果，是反刍家畜安全、高效的粗蛋白质营养日粮。     

尿中嘌呤衍生物是估测瘤胃微生物合成量的一种指示物

确定瘤胃微生物细胞净合成量对反刍动物营养十分重要。这是因为微生物蛋白质量是反刍动物宿主对蛋白质需要的重要来源。用标记物和在动物小肠安装瘘管的方法来测定瘤胃合成的净微生物细胞量或微生物细胞进入下一级消化道的数量不仅费时，且精度不高。Ｌｉｎｇ等（１９７８）研究了许多用以区分进入绵羊小肠食糜中微生物蛋白质的微生物标记物。食糜中ＲＮＡ与总氮比率是一种测定进入十二指肠食糜氮中微生物氮含量的适宜标记物。然而Ｂｒｏｄｅｒｉｃｋ等（１９９２）认为常用的微生物标记物（嘌呤、ＲＮＡ、ＤＮＡ、二氨基庚二酸及同位素标记…     

反刍动物瘤胃内含氮化合物代谢研究概况

反刍动物瘤胃内的含氮化合物主要包括蛋白质、核蛋白和非蛋白氮（NPN）等，它们主要来源于饲料、微生物蛋白（MCP）、脱落的上皮细胞和循环进入瘤胃的尿素。     

影响反刍动物蛋白质利用率的因素

反刍动物蛋白质来源于微生物蛋白（MCP）、瘤胃非降解饲料蛋白质（UDP）及极少量的内源蛋白质（ECP）。其中,影响MCP合成的因素主要有饲料蛋白质的组成及含量、饲料中碳水化合物含量、饲料的维生素矿物质以及瘤胃的微生物组成和pH值；     

过瘤胃氨基酸的研究

蛋白质是反刍动物日粮中主要限制性营养成分之一，在反刍动物营养中，日粮蛋白在瘤胃中降解是一种低效的营养过程。在有些条件下仅靠饲喂高蛋白日粮也不一定能提高反刍动物生产性能。为了减少瘤胃内蛋白质的降解损失，人们采取各种措施以提高日粮中蛋白质的过瘤胃值（斯钦，1996）。研究发现，单靠增大过瘤胃蛋白的量，并不一定能保证家畜增产，蛋白质对反刍动物的。     

奶牛过瘤胃氨基酸的研究进展

约在１９４２年 ,科学家发现经加热处理的大豆饼 ,添加蛋氨酸后能改善其营养价值 ,于是才开始将氨基酸用作配合饲料的添加物。但氨基酸在饲料中的应用 ,主要限于猪、鸡等单胃动物。关于反刍动物利用氨基酸的研究 ,最初只是从瘤胃微生物的营养需要方面来考虑的。但对于高产反刍动物（如高产奶牛） ,仅靠瘤胃微生物合成的菌体蛋白质不能满足其对蛋白质的需要 ,直到２０世纪７０年代后期 ,人们才加快了对反刍动物利用氨基酸的研究步伐。氨基酸在反刍动物饲料中的添加利用 ,比在猪、鸡中困难 ,因为牛、羊的瘤胃具有发酵降解功能 ,能使添加的氨基…     

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.     

不同纤维素与淀粉比率等氮纯化底物瘤胃发酵微生物蛋白质合成量

采用持续动态瘤胃模拟装置 (RSI)研究了 6种不同纤维素和淀粉比率 (C S) :0 .14、0 .44、0 .94、1.92、4.75、15 .76,等氮 ( 14.2 2 % ,风干物质基础 )纯化底物养分瘤胃发酵微生物组分及微生物蛋白质合成量。结果显示 :微生物有机物中氮的含量MN MOM在 5 5 0 %～ 6 64 %之间 ;微生物有机物中RNA含量 (RNA MOM ,% )不受日粮C S影响(P >0 0 5 ) ,仅发现微生物氮含量受到日粮碳水化合物比率影响 (P <0 0 5 )。 72小时发酵后 ,瘤胃微生物蛋白质合成效率与底物纤维素和淀粉比率成乘幂负相关关系 :MN RDN =0 .764 9(C S) - 0 .1 0 6 3,n =6,R =- 0 .93 1;MN FOM(g kg) =2 3 .88(C S) - 0 .0 988,n =6,R =- 0 .881。结果表明 ,在瘤胃可利用氮相同条件下 ,微生物蛋白合成效率取决于适宜的底物结构性碳水化合物和非结构性碳水化合物比率     

Effect of Fusarium toxin-contaminated triticale and forage-to-concentrate ratio on fermentation and microbial protein synthesis in the rumen

In this study, the effect of Fusarium toxin-contaminated triticale (FUS) at high (60%) and low (30%) concentrate proportion in ruminant rations on ruminal fermentation, microbial protein synthesis and digestibility was investigated, using in vivo and in vitro methods. Significant effects of the forage-to-concentrate ratio on ruminal degradation and digestibility of crude nutrients and detergent fibre fractions as well as on the pH value and the concentration of short chain fatty acids (SCFA) in rumen fluid were found. The production of SCFA was affected, and the degradation of crude fibre and neutral detergent fibre in the rumen was reduced by the inclusion of FUS at high concentrate proportion. The efficiency of microbial crude protein synthesis was higher in diets with 60% than in diets with 30% concentrates, but was impaired in the presence of FUS in vitro at the high concentrate level. Marginal effects of FUS on the amino acid pattern of microbial protein were detected. It was concluded that the use of FUS in high concentrate diets can influence ruminal fermentation and microbial protein synthesis at a dietary deoxynivalenol concentration below 5 mg/kg dry matter.     

能量溢出与储备碳水化合物合成对瘤胃微生物生长效率影响的研究进展

瘤胃微生物将一些ATP用来维持代谢,剩余的ATP用来进行储备碳水化合物合成和能量溢出（进行无效循环并产热）,因此,瘤胃微生物蛋白质合成效率较低。瘤胃原虫贮存的碳水化合物占绝大部分。在一些细菌纯培养实验中发现有能量溢出,最近研究发现在混合瘤胃菌群中也能发生能量溢出。通过精确测定碳水化合物贮存和能量溢出的量,以及二者对微生物生长效率的影响,可以预测微生物蛋白质产量,制定提高瘤胃微生物蛋白质生产效率的措施。综述了瘤胃微生物能量溢出和糖原储备规律方面的研究进展,以期为估测微生物蛋白质合成量,提高饲料蛋白质利用效率提供参考。     

Urea transport and hydrolysis in the rumen: A review

Inefficient dietary nitrogen (N) conversion to microbial proteins, and the subsequent use by ruminants, is a major research focus across different fields. Excess bacterial ammonia (NH₃) produced due to degradation or hydrolyses of N containing compounds, such as urea, leads to an inefficiency in a host's ability to utilize nitrogen. Urea is a non-protein N containing compound used by ruminants as an ammonia source, obtained from feed and endogenous sources. It is hydrolyzed by ureases from rumen bacteria to produce NH₃ which is used for microbial protein synthesis. However, lack of information exists regarding urea hydrolysis in ruminal bacteria, and how urea gets to hydrolysis sites. Therefore, this review describes research on sites of urea hydrolysis, urea transport routes towards these sites, the role and structure of urea transporters in rumen epithelium and bacteria, the composition of ruminal ureolytic bacteria, mechanisms behind urea hydrolysis by bacterial ureases, and factors influencing urea hydrolysis. This review explores the current knowledge on the structure and physiological role of urea transport and ureolytic bacteria, for the regulation of urea hydrolysis and recycling in ruminants. Lastly, underlying mechanisms of urea transportation in rumen bacteria and their physiological importance are currently unknown, and therefore future research should be directed to this subject.     

Comparative characterization of reticular and duodenal digesta and possibilities of estimating microbial outflow from the rumen based on reticular sampling in dairy cows

The objective of this experiment was to investigate the possibility of estimating the outflow of nutrients and microbial protein from the rumen based on sampling reticular contents as an alternative to duodenal sampling. Microbial protein flow estimates were also compared with a third method based on sampling of ruminal contents. Reticular and duodenal digesta and ruminal contents were recovered from 4 cows used in a 4 x 4 Latin square design experiment, in which the ruminal effects of 4 exogenous enzyme preparations were studied. Large and small particulate and fluid markers were used to estimate digesta flow in a triple-marker model; 15N was used as a microbial marker. Reticular and duodenal digesta were segregated into small and large particles (SP and LP, respectively) and a fluid phase, and ruminal digesta was segregated into particulate and fluid phases. Compared with digesta recovered at the duodenum, reticular digesta had lower OM and greater NDF contents. The proportion of microbial N was notably greater in the fluid phase of reticular digesta. Ruminal outflow of DM and OM was greater (by 17 and 28%) and that of NDF was lower (by 14%) when estimated from duodenal compared with reticular samples. There was no difference in the estimated flow of starch and nonammonia and microbial N between the reticular and duodenal techniques. Microbial N flow estimated based on ruminal sampling was similar to those based on duodenal and reticular sampling. The ruminal method, however, grossly overestimated flow of DM, OM, and NDF. This study supports the concept that microbial protein outflow from the rumen can be measured based on sampling of ruminal or reticular digesta. The reticular sampling technique can also provide reliable estimates for ruminal digestibility of OM, N, and fiber fractions. These findings need to be confirmed in experiments with basal diets varying in structure and forage-to-concentrate ratios.     

Comparative investigation of salinomycin and flavophospholipol in sheep fed different composed diets.

The effects of salinomycin and flavophospholipol, and their relationship with the diet, were studied in nine ruminally and duodenally cannulated wethers. Within the composition of the ration, the levels of rumen degradable protein (RDP) and non-structural carbohydrates (NSC) were changed (diet H: 74% RDP and 38% NSC; diet M: 57% RDP and 32% NSC; diet L: 48% RDP and 23% NSC). There was no clear treatment effect of flavophospholipol on propionate concentration. Salinomycin supplementation appeared to be more effective than flavophospholipol in the increase of propionate concentration at the expense of acetic acid. Salinomycin significantly reduced the ammonia concentration of the rumen fluid. Microbial N content of the duodenal digesta was significantly lower when salinomycin was used. Salinomycin inhibited proteolysis and reduced the efficiency of microbial protein synthesis. The effect of salinomycin on ruminal N metabolism was independent of the composition of substrate. Unlike salinomycin, flavophospholipol tended to increase proteolysis in the rumen and did not inhibit protein synthesis. The effect of salinomycin on ruminal fermentation and the duodenal flow of nutrients were independent of substrate composition.     

Quantification of intraruminal recycling of microbial nitrogen using nitrogen-15.

Studies were done to derive a technique to quantify intraruminal recycling of microbial nonammonia nitrogen (NAN). After dosing 15NH4+ into the rumen, ruminal NH3N and NAN pools were sampled over time for analyses of 15N enrichment. Compartmental analysis of both pools was used to quantify the percentage of microbial NAN that recycles in the rumen. Microbial NAN does not need to be fractionated from total NAN, assuming that only microbial NAN becomes labeled with 15N and that the ratio of microbial NAN:nonmicrobial NAN remains constant over time. Based on the data obtained from eight nonlactating cattle fed 85% corn silage diets at 1.5 to 1.0% BW, percentage of intraruminal recycling of microbial NAN was related to efficiency of bacterial protein synthesis (grams of CP/100 g of OM truly digested) in a curvilinear manner (y = 100 - .073x2). From this function, recycling was predicted to be approximately 75% for dairy cows consuming 50:50 forage:concentrate diets at 3.5% of BW. However, more data are needed to evaluate intraruminal recycling of microbial NAN using this technique under different dietary conditions.     

瘤胃微生态种群对宿主动物氮源物质的调节作用研究

瘤胃微生物如细菌、原虫以及纤毛虫等的研究一直是反刍动物研究的重要方面。它们不仅可以对饲料纤维、淀粉进行降解,日粮蛋白质也是它们的发酵底物之一,此外,内源性的含氮物质和日粮中添加的氮源物质都可被它们代谢利用。在瘤胃微生物产生的各种降解酶的作用下,饲料养分被逐级降解进行转化,但它们的作用机理及相互作用尚不完全清楚,一直是反刍动物营养研究的重点。为此,文章对瘤胃微生物对宿主动物氮源物质的作用及其需求作一介绍,以便为深入研究作一参考。     

日粮降解氮转化为瘤胃微生物氮效率影响因素的研究

用１０种不同氮源日粮（４种糊化淀粉尿素日粮、常规尿素日粮、豆饼日粮、甲醛及非甲醛新保护剂保护豆饼日粮）在５头装有瘤胃和真胃瘘管的阉牛中分别进行６×５和４×４两个拉丁方试验，用体内法测定日粮的蛋白质和有机物质的降解率、微生物蛋白质产量及瘤胃氨浓度。同时用瘤胃尼龙袋法测定蛋白质和有机物质降解率。结果表明：不同氮源日粮间降解氮转化为微生物氮的效率差异明显（Ｐ＜０．０１）：降解氮转化效率与瘤胃平均氨浓度有限高曲线负相关（ｒ＝－０．９１９２），与降解氮同体内法测定的瘤胃可消化有机物（ＲＤＯＭ）及瘤胃尼龙袋法测定的瘤胃２４小时可发酵有机物（ＦＯＭ）的比率均有同种类型的曲线负相关（ｒ＝－０．８７９６，ｒ＝－０．９０３７）。说明降解氮转化为微生物氮的效率受饲料蛋白质降解量、降解速度及降解氮与微生物可利用能平衡的影响。