分解代谢物控制蛋白A对瘤胃中牛链球菌碳水化合物代谢的调控作用

分解代谢物控制蛋白A(CcpA)是低GC含量的革兰氏阳性菌基因转录的抑制或激活因子,对瘤胃微生物代谢具有调控作用。瘤胃中主要乳酸产生菌——牛链球菌(S.bovis)中的CcpA与磷酸转移酶系统(PTS)有着密切关系,对碳源次序代谢利用及碳水化合物代谢的多种关键酶具有重要的调控作用。本文综述了有关CcpA对S.bovis碳水化合物的代谢调控的研究进展,旨在为后期进一步研究S.bovis代谢产酸机制、防控反刍动物瘤胃酸中毒提供思路和参考。     

瘤胃中乳酸的代谢及其调控机制

有关瘤胃酸中毒发生机制研究表明,瘤胃乳酸的累积可能对酸中毒诱导起重要作用,而高精料日粮下瘤胃乳酸累积主要取决于瘤胃乳酸产生菌和乳酸利用菌间的平衡程度。本文综述了瘤胃微生物对乳酸的代谢机制,包括主要乳酸产生菌[溶纤维丁酸弧菌(Butyrivibrio fibrisolvens)、牛链球菌(Streptococcus bovis)、乳酸杆菌(Lactobacillus)]和主要乳酸利用菌[反刍兽新月单胞菌(Selenomonus ruminantium)、埃氏巨型球菌(Megasphaera elsdenii)],并简要概述了酸中毒的调控方法,旨在为反刍动物瘤胃酸中毒的乳酸中毒机制深入解析提供参考。     

瘤胃代谢调控对牛代谢生理影响的研究

本研究对牛瘤胃代谢调控的机理了初步探讨,其作用原理是促进瘤胃内环境发生改变来影响牛的代谢生理,表现为血液生理指标的变化,瘤胃代谢调控后,瘤胃内ｐＨ值提高１０．８２％,达到６．７６,微生物总数１１．２８×１０＾９个,增加１．４６３倍,血浆中血糖和胆固醇的水平分别提高５５．７２％,５８．６％,尿素氮素浓度降低了３９．１５％,经ｔ检验,以上各指标试验组和对照组差差异达以级显著（Ｐ〈０．０１）或显著水平（     

反刍动物瘤胃乳酸代谢及其调控的研究进展

反刍动物采食大量的高精饲料后,瘤胃中乳酸会大量积累导致瘤胃酸中毒。本文针对"乳酸中毒学说"综述乳酸在瘤胃中的代谢情况与相关瘤胃微生物代谢以及乳酸中毒调控的部分措施,以期为实际生产提供有用的理论依据。     

反刍动物瘤胃内乳酸代谢与瘤胃酸中毒调控的研究进展

乳酸是反刍动物瘤胃内重要的中间代谢产物,在饲喂高精料的反刍动物瘤胃内乳酸累积过多可能会加速瘤胃酸中毒的进程。本文综述了瘤胃内乳酸代谢机制和影响因素,以及提高乳酸利用和添加硫胺素等预防瘤胃酸中毒的几种方式,旨在系统地总结反刍动物瘤胃内乳酸代谢机制,为瘤胃酸中毒的调控提供理论支撑。     

反刍动物发生瘤胃酸中毒的营养机制及其防治

瘤胃酸中毒是危害反刍动物常见的一种代谢病。其产生的主要原因是反刍动物日粮中含有大量易发酵的碳水化合物饲料或者日粮粗纤维含量较低,导致瘤胃产生乳酸过多,引起瘤胃微生物区系失调和瘤胃功能紊乱而造成的。本文就酸中毒的发病机理、防治措施等几方面进行了论述。     

牛瘤胃急性酸中毒的治疗

牛瘤胃急性酸中毒的治疗哈尔滨动植物检疫局（１５００３６）龙呈祥译马思奇校牛食过量的甜菜和玉米穗后，会使其瘤胃的消化过程受到破坏，瘤胃内容物ｐＨ值由６．５—７．２降到３．７—４．３时，瘤胃微生物区系参与分解氨基酸而形成生物胺（组胺、丁二胺、戊二胺等），...     

一起急性牛瘤胃酸中毒的治疗体会

瘤胃酸中毒是复胃动物的常见病和多发病,它是由于采食了过量的含碳水化合物丰富的饲料后,在瘤胃中分解发酵、导致瘤胃内微生物群落失调,产生大量乳酸、瘤胃内pH值下降,继而引起瘤胃积食滞留和机体乳酸中毒症状.本病以发病突然、死亡迅速,并以严重的毒血症、脱水、瘤胃鼓胀、肠胃蠕动停滞和高度虚弱为特征的急性中毒疾病.     

牛瘤胃酸中毒的综合防治

当牛采食大量易发酵的饲料后容易在瘤胃中产生大量乳酸,引起乳酸中毒。瘤胃酸中毒既是乳酸中毒也是瘤胃积食,但发病剧烈,死亡率高,对牛只的影响较大。本文就瘤胃酸中毒的病因、临床症状、诊断方法和综合防治进行简要阐述,为在牛只养殖过程中预防瘤胃酸中毒提供理论基础。     

牛瘤胃酸中毒的诊治报告

牛瘤胃酸中毒是因牛采食大量富含淀粉、糖类的饲料后,在瘤胃内发酵产生大量乳酸, 乳酸被吸收而引起酸中毒。临床上以消化不良、脱水、酸中毒及神经症状为主。发病急、病程短、死亡率高。对养牛业危害严重。 我校兽医院在几年来的临床诊疗工作中遇到过几例,现将典型病例的诊治情况报告如下。     

Cloning and characterization of the glutamate dehydrogenase gene in Streptococcus bovis

Streptococcus bovis, an etiologic agent of rumen acidosis in cattle, is a rumen bacterium that can grow in a chemically defined medium containing ammonia as a sole source of nitrogen. To understand its ability to assimilate inorganic ammonia, we focused on the function of glutamate dehydrogenase. In order to identify the gene encoding this enzyme, we first amplified an internal region of the gene by using degenerate primers corresponding to hexameric family I and NAD(P)⁺ binding motifs. Subsequently, inverse PCR was used to identify the whole gene, comprising an open reading frame of 1350 bp that encodes 449 amino acid residues that appear to have the substrate binding site of glutamate dehydrogenase observed in other organisms. Upon introduction of a recombinant plasmid harboring the gene into an Escherichia coli glutamate auxotroph lacking glutamate dehydrogenase and glutamate synthase, the transformants gained the ability to grow on minimal medium without glutamate supplementation. When cell extracts of the transformant were resolved by blue native polyacrylamide gel electrophoresis followed by activity staining, a single protein band appeared that corresponded to the size of S. bovis glutamate dehydrogenase. Based on these results, we concluded that the gene obtained encodes glutamate dehydrogenase in S. bovis.     

Effects of lauric acid on physical, chemical and microbial characteristics in the rumen of steers on a high grain diet

The effects of being fed lauric acid on rumen characteristics were evaluated in a double 3 × 3 Latin square design using six Holstein steers with ruminal cannulas on a high grain diet. The steers were fed commercial concentrate (8.7 kg/day/steer) with one of three levels of lauric acid (0, 25 or 50 g/day/steer) and timothy hay (1.8 kg/day/steer). The feed intake and digestibility were determined. Ruminal fluid was collected at 3 h after feeding to determine chemical, physical and microbial parameters. An in vitro pure culture study was performed to determine the effects of lauric acid on Streptococcus bovis, a potent bloat‐ and acidosis‐promoting rumen bacterium. There were no differences in feed intake and digestibility among the treatments. The proportion of butyrate and the viscosity of the rumen fluid tended to be lowered (P < 0.08 and P < 0.09, respectively) and the stable ingesta volume increase was significantly decreased (P < 0.01) by the lauric acid feed. The abundance of protozoa and bacteria did not differ among the treatments. In the in vitro study, the growth of S. bovis was inhibited by the lauric acid (100 nmol/L) but it showed an adaptive growth to lauric acid in long‐term subculturing. The S. bovis that had adapted to lauric acid showed decreased viscosity and lactate production (P < 0.01) in culture with sucrose. These results indicate that supplemental lauric acid added to a high grain diet improves physical properties, possibly by altering the metabolic activity of S. bovis, and it may prevent the occurrence of feedlot bloat and acidosis in beef cattle.     

体外法研究烟酸对牛链球菌乳酸发酵的影响

本试验旨在研究不同水平烟酸对牛链球菌乳酸发酵的影响.采用单因素完全随机试验设计分为4组,分别在培养液中添加0(对照)、0.05、0.25、0.50 mg/mL烟酸,每组4个重复.39℃体外培养0、2、4、6、12、24 h后,测定培养液菌群密度、pH,测定12 h培养液的乳酸发酵指标和烟酰胺腺嘌呤二核苷酸浓度.结果表明,随着烟酸添加量的增加,菌群密度呈现下降的趋势,0～24 h平均菌群密度0.50 mg/mL烟酸组最低,极显著低于其他各组(P＜0.01).烟酸显著或极显著提高了2～24 h培养液pH(P＜0.05或P＜0.01).烟酸对单位密度细菌耗糖速率没有显著影响(P＞0.05),但0.25、0.50 mg/mL烟酸组显著降低了单位密度细菌乳酸产量(P＜0.05),极显著降低了产乳酸效率(P＜0.01);试验组乳酸脱氢酶活性均显著或极显著高于对照组(P＜0.05或P＜0.01).烟酸对培养液氧化态烟酰胺腺嘌呤二核苷酸(NAD+)浓度没有显著影响(P＞0.05),但随着烟酸添加量的提高,还原态烟酰胺腺嘌呤二核苷酸浓度增加,且各组间差异极显著(P＜0.01).本试验条件下,烟酸可抑制牛链球菌增殖,并保证NAD+的稳定供给,维持了糖酵解的进行,减少了乳酸的生成,提高了培养液pH,其中以0.50 mg/mL的添加量效果最好.     

Immunization with a Streptococcus bovis vaccine administered by different routes against lactic acidosis in sheep

Streptococcus bovis is an important lactic acid bacterium in the rumen, which contributes to the development of lactic acidosis. This study was designed to test the efficacy of immunization with S. bovis primed either intramuscularly (i.m.) or intraperitoneally (i.p. ) against lactic acidosis. Forty-five wethers were allocated to three treatment groups. Two groups were injected with a S. bovis vaccine by either the i.m. or i.p. route for primary immunization; both groups were further immunized by the same route(s) (oral and/or i.m.) for boosters. The third group was not immunized (control). Antibody concentrations were measured in saliva prior to and following animals being fed a grain diet, and also in the rumen fluid, before the animals were suddenly introduced to a grain diet. The average antibody concentration in the animals of the i.m. group was higher than the i.p. group (P< 0.05). The antibody concentration in the rumen fluid of immunized sheep was higher than the control animals (P< 0.01). The difference in the rumen fluid antibody concentration between the i.m. and i.p. groups was not statistically significant (P> 0.05). In the i.m. group, there was a significantly greater feed intake, higher rumen pH, lower diarrhoea scores, and less increase in blood packed cell volume following grain feeding than in the animals of the control group. The severity of diarrhoea and the increase of blood packed cell volume in the animals of the i. p. group were also less than in the animals of the control group. The results suggest that the risk of lactic acidosis can be reduced by immunization against S. bovis, and that the immunization primed i. m. is more effective than the immunization primed i.p.     

山羊瘤胃内产乳酸菌的分离鉴定及其产D-、L-乳酸特性的研究

为阐明瘤胃中产乳酸菌的种类及其产乳酸特性,本试验以饲喂精粗比例为6:4的健康山羊瘤胃液为接种物,利用厌氧分离技术,经形态学和16s rRNA序列分析法,从山羊瘤胃中分离获得6株细菌(分别命名为L2、L3、L5、L8、L10和L12).菌株主要为3类:L2、L8、L10为牛链球菌,L5为马链球菌,L3和L12为食窦魏斯氏...     

反刍动物瘤胃发育规律及其调控机制研究进展

瘤胃是反刍动物至关重要的消化吸收器官,部分降解的营养物质可直接通过瘤胃上皮被机体吸收和利用。因此,瘤胃的发育程度与反刍动物的生产性能密切相关,而瘤胃发育充分且功能健全是反刍动物最佳生产性能得以发挥的前提条件。然而,幼龄反刍动物瘤胃的生理结构及其功能均发育不完善,需在固体饲料、断母乳等外界刺激下完成经由非反刍阶段向反刍阶段转变的复杂过程,进而才可发挥其重要功能。目前,如何掌握并遵循瘤胃的发育规律,在保证瘤胃充分发育且功能完善的情况下,对幼龄反刍动物实施早期断奶技术,已成为现代反刍动物养殖生产中亟需解决的问题之一。作者就反刍动物瘤胃发育进程中瘤胃微生物菌群的时空演变、瘤胃组织形态学发育和代谢改变及瘤胃发育调控机制进行综述,由生理结构至功能逐层对反刍动物瘤胃的发育规律进行全面总结,阐明影响反刍动物瘤胃发育的相关因素及其可能的调控机制。本文旨在进一步丰富与瘤胃发育相关的理论基础,以期为利用瘤胃发育规律开发促进反刍动物瘤胃发育的营养调控策略提供科学支撑,为挖掘幼龄反刍动物的生产潜力提供新思路。