不同瘤胃乙、丙酸比例对绵羊体内氧化代谢的影响

试羊不喂料 ,由瘤胃和真胃瘘管均衡灌注营养液以达到恒态代谢。改变瘤胃灌注混合挥发性脂肪酸的乙、丙酸比例 ,测定由血管插管注入 14C—乙酸后血液CO2 放射比强度(SA)变化曲线。结果表明 ,灌注高乙、丙酸比例的混合挥发性脂肪酸时 ,血液CO2的SA—时间曲线的K值较大 ,体内代谢物的氧化代谢速度加快。     

挥发性脂肪酸在动物体内的作用

挥发性脂肪酸 (volatilefattyacids ,VFA)是碳链为 1～ 6的脂肪酸 ,包括乙酸、丙酸、丁酸、异丁酸、戊酸、异戊酸等 ,其中对动物体代谢作用最为重要的有直链乙酸、丙酸和丁酸 ,约占瘤胃发酵VFA总产量的 95 % ,乙酸是产量最大的VFA ,约占VFA总产量的 70 %～ 75 %。挥发性脂肪酸在不同动物体内其比例和数量不同 ,见表 1。表 1　食糜挥发性脂肪酸浓度及其中各酸比例绵羊瘤胃猪盲肠鸡盲肠总挥发性脂肪酸 (mmol/L) 1 1 91 8 2 1 0 7乙酸 (% ) 54 55 61丙酸 (% ) 2 5 2 7 2 7丁酸 (% ) 1 7 6 1 1长链脂肪酸 (% ) 4 2 1　　注 :资料来源于…     

不同瘤胃乙、丙酸比例对绵羊丙酸糖异生和葡萄糖周转速度的影响

本项试验使用了 14C标记的丙酸和葡萄糖 ;用同位素示踪技术研究了全营养灌注绵羊改变瘤胃灌注混合挥发性脂肪酸中乙/丙酸比例后 ,丙酸糖异生代谢和体内葡萄糖周转速度的变化。结果表明 ,灌注乙/丙酸比例为75 :15的混合挥发性脂肪酸时 ,葡萄糖碳原子中来自丙酸的碳原子比例(P<0.01)和体内葡萄糖周转速度(P<0.05)均高于灌注其它乙/丙酸比例的混合挥发性脂肪酸。本研究结果为粗饲料代谢能利用效率低于精饲料是由于体内葡萄糖供给不足的观点提供了依据     

瘤胃灌注乙丙酸不同摩尔比混合挥发性脂肪酸对奶山羊乳脂合成的影响

4只安装永久性瘤胃瘘管和颈动脉插管的泌乳中后期文登奶山羊,采用4×4拉丁方试验设计,试验处理为瘤胃连续灌注4种不同比例的混合挥发性脂肪酸(VFA)溶液,4种灌注液的乙酸/丙酸/丁酸摩尔比依次为:75:15:10(VFA1),65 : 25:10(VFA2),55:35;10(VFA3)和45 : 45 :10(VFA4).日粮(精粗比为45:55)制作为颗粒料,每2 h自动饲喂1次,瘤胃灌注的VFA按奶山羊维持需要的30%确定.研究表明,灌注液对奶产量、乳糖的影响不显著(P>0.05),高丙酸灌注组乳脂率、乳脂量显著下降(P<0.05);血浆胰岛素水平呈上升趋势(P>0.05),血糖浓度处理间无显著变化(P>0.05).随灌注液丙酸摩尔比的升高,颈动脉血浆乙酸、NEFA、BHBA浓度下降(P<0.05),丙酸浓度上升(P<0.05),TG和丁酸浓度组间差异不显著(P>0.05);动脉血浆BHBA、NEFA、TG和丁酸的乳腺吸收率降低(P<0.01),丙酸的乳腺吸收率升高(P<0.01),乙酸的乳腺吸收率未出现显著变化(P>0.1).随灌注液丙酸摩尔比的升高,乳脂中中链脂肪酸(C10-C16)和中短链脂肪酸(CA-C16)的含量呈上升趋势(P<0.05),长链脂肪酸(≥C16)的含量呈下降趋势(P<0.05),其中VFAl组C10-C16及CA-C16含量均低于其它3组(P<0.05),≥C16含量显著高于其它3组(P<0.05);Trans-10,cis-12CLA无显著变化(P>0.05).研究结果表明,提高瘤胃灌注VFAs混合液的丙酸摩尔比可引起乳脂率的降低,抑制乳腺对NEFA的吸收,增加乳脂中CA-C16脂肪酸的比例,降低≥C16脂肪酸的比例.     

反刍动物挥发性脂肪酸的研究进展

自John Barcroft等(1944)发现碳水化合物在瘤胃中发酵产生的挥发性脂肪酸(VFA)是反刍动物的主要能源之后,很多学者对VFA的吸收与中间代谢和不同种类饲料瘤胃VFA的产量及其乙酸、丙酸和丁酸的摩尔比例的组成进行了大量研     

不同营养水平对牦牛瘤胃内VFA的影响

应用气相色谱法,在维持型(略低于维持水平)、粗料型、精料型三种不同营养条件下测定了牦牛瘤胃内挥发性脂肪酸(VFA)的组成及含量。结果表明:维持组除丙酸及C_2/C_3比例极显著(P<0.01)低于粗料组外,其它无差异(P>0.05);精料组的总挥发性脂肪酸(TVFA)和乙酸高于粗料组(P<0.05),但C_2/C_3比例相同,二者属同一发酵类型。丙酸、丁酸含量高于其它动物是牦牛瘤胃代谢的特点。     

静脉注射挥发性脂肪酸钠盐溶液对绵羊瘤胃运动的影响

实验以颈静脉分别注射乙酸、丙酸、丁酸的钠盐溶液模拟反刍动物采食后血液中挥发性脂肪酸(VFA,下同)升高的状况;以瘤胃平滑肌电为瘤胃消化运动的指标,研究了绵羊血液中VFA对瘤胃消化运动的影响。结果表明:0.2M的乙酸钠50ml,丙酸钠5ml或丁酸钠2.5ml可增强瘤胃运动的频率和强度:而1M的乙酸钠50ml、丙酸钠5ml或丁酸钠2.5ml对瘤胃运动的频率和强度有抑制作用。三种VFA钠盐的作用强弱顺序是:丁酸钠>丙酸钠>乙酸钠。     

不同加工处理日粮对绵羊瘤胃挥发性脂肪酸的影响

选用3只健康并安装永久性瘤胃瘘管的杂种羯羊,平均体重为24 kg,采用3×3无重复拉丁方试验设计,用3种不同日粮(全混合颗粒料日粮、粉碎精料+铡短粗料日粮和未粉碎精料+铡短粗料日粮)来研究对绵羊瘤胃挥发性脂肪酸(VFA)浓度的影响。结果表明,采食未粉碎精料+铡短粗料日粮绵羊的瘤胃总挥发性脂肪酸(TVFA)浓度显著高于采食全混合颗粒料日粮绵羊(P＜0.05),采食未粉碎精料+铡短粗料及粉碎精料+铡短粗料日粮的绵羊瘤胃丙酸摩尔比显著或极显著高于采食全混合颗粒料日粮绵羊(P＜0.05,P＜0.01),而(戊酸+异戊酸)摩尔比极显著低于全混合颗粒料日粮绵羊(P＜0.01),乙酸/丙酸显著或极显著低于采食全混合颗粒料日粮绵羊(P＜0.05,P＜0.01)。因此,用粉碎精料+铡短粗料或未粉碎精料+铡短粗料日粮饲喂绵羊能改善绵羊瘤胃发酵类型。     

基于Actinomyces ruminicola的微态制剂的体外发酵效果

为了研制一种新的微生态制剂,试验利用分离得到的瘤胃厌氧菌Actinomyces ruminicola(命名为NY2)与痤疮丙酸杆菌混合制成微生态制剂进行体外发酵,研究微生态制剂的体外发酵特性及产挥发性脂肪酸的能力,确定微生态制剂中Actinomyces ruminicola与痤疮丙酸杆菌的最佳混合比例。结果表明:当微生态制剂中Actinomyces ruminicola与痤疮丙酸杆菌混合比为1∶1时,培养瓶中乙酸、丙酸、丁酸和总挥发性脂肪酸的浓度最高值分别达到91.07,41.12,27.58,169.19 mmol/L。该比例微生态制剂可保持瘤胃内容物pH值在6.0左右波动,有利于瘤胃微生物发酵,并能促进乙酸、丙酸等挥发性脂肪酸的生成。     

瘤胃乙酸与丙酸摩尔比例的改变对瘤胃发酵及血液指标的影响

通过向瘤胃灌注乙酸：丙酸：丁酸的摩尔比例分别为75：15：10，65：25：10，55：35：10和45：45：10溶液，并在连续灌注的作用下，以期达到最终改变瘤胃液中乙酸：丙酸：丁酸摩尔比例的目的。研究表明：（1）随着灌注液中丙酸浓度的提高，最终瘤胃液中丙酸的比例增加，乙酸的比例逐渐下降，与对照组差异显著（P＜0.05），丁酸的摩尔比例无论与对照组，还是各处理间均无差异；（2）向瘤胃灌注的VFA溶液提供高于维持能量水平30％以上的能量，使瘤胃中总的VFA浓度、VFA产生速率、丙酸的产生速率及VFA的总产量均显著增加（P＜0.01）；但是对基础混合日粮的干物质（DM）、有机物（OM）、中洗纤维（NDF）、酸洗纤维（ADF）、半纤维素（HCF）等养分的消化率不构成显著影响；（3）当灌注溶液中丙酸所占摩尔比例增加到35％，粪氮和尿氮的排出量显著减少（P＜0.05），从而提高日粮氮的沉积能力。进一步研究表明，当灌注液中丙酸的摩尔比例进一步提高至45％时，血糖浓度及胰岛素的浓度才显著增加（P＜0.05）；但胰岛素与胰高血糖素的比值对于不同的处理或对照组，基本保持稳定。     

Forestomach epithelial receptor activation by rumen fluids from sheep given intraruminal infusions of volatile fatty acids

Forty-four reticuloruminal epithelial receptors were tested with rumen fluids obtained from 12 sheep before they were intraruminally infused with 4.0M acetic acid (8 sheep) or 4.0M butyric acid (4 sheep; preinfusion rumen fluid) and with rumen fluids obtained at the onset of ruminal stasis (abolition rumen fluid). The preinfusion rumen fluids from the 8 acetic acid-infused sheep (mean pH, 6.55) contained 1.7 mM nondissociated volatile fatty acids (VFA)/L and excited none of the 25 receptors tested. Preinfusion rumen fluids from the 4 butyric acid-infused sheep (mean pH, 6.98) contained 0.3 mM nondissociated VFA/L and also did not evoke responses in any of the 19 receptors tested. Abolition rumen fluids from sheep treated with acetic acid excited 17 of the 25 receptors tested and contained 89.4 mM nondissociated VFA/L, of which nondissociated acetic acid comprised 85.0 mM/L. Abolition rumen fluids from sheep treated with butyric acid activated 14 of the 19 receptors tested and contained 61.1 mM nondissociated VFA/L, of which 38.7 mM/L was nondissociated butyric acid. Preinfusion rumen fluids whose pH values were adjusted to that of abolition rumen fluids with HCl contained nondissociated VFA levels ranging from 16.3 mM/L (acetic acid-treated sheep) to 20.6 mM/L (butyric acid-treated sheep) and elicited responses in 4 of 30 receptors tested. Preinfusion rumen fluids whose pH values were adjusted to the pH value of abolition rumen fluid with acetic acid contained 29.5 mM nondissociated VFA/L and excited 7 of 13 tested receptors.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of ruminal infusion of volatile fatty acids on plasma concentration of growth hormone and insulin in sheep.

In an initial experiment we observed postprandial changes in plasma concentrations of growth hormone (GH), insulin, glucagon, and somatostatin (SRIF) in sheep. We then examined whether increasing the rumen concentration of volatile fatty acids (VFA) by infusing a VFA mixture at three rates (53.5, 107, and 214 micromol/kg/min for 4 hr) mimicked the postprandial changes in hormone secretion. Feeding significantly (P < 0.05) suppressed the plasma GH concentration for 6 hr, whereas it significantly (P < 0.05) increased plasma concentrations of insulin, glucagon, and SRIF. Plasma glucose levels tended to decrease after feeding but then gradually increased over the prefeeding level (P < 0.05). Intraruminal infusion of the VFA mixture at 107 micromol/kg/min caused similar changes in ruminal VFA concentrations to those seen after feeding. The infusion significantly (P < 0.05) suppressed GH secretion in a dose-dependent manner, whereas it caused a significant (P < 0.05) increase in insulin and glucose concentrations without changing glucagon concentrations. From these results, we conclude that the postprandial change in ruminal VFA concentration may be a physiological signal which modifies GH and insulin secretion in sheep.     

Ammonia, pH and volatile fatty acids in the bovine rumen after feeding with hay.

The effect of feeding level and interval between feedings on the fermentation pattern in the bovine rumen have been investigated in experiments with hay. The animals were completely adapted heifers fitted with rumen cannulas, and the parameters measured were ammonia, pH, volatile fatty acids (VFA) and non-glucogenic/glucogenic ratio (NGGR) in the VFA mixture.Increasing feeding levels, ranging from 2/3 to 4/3 of maintenance level, resulted in higher average concentrations of VFA and lower pH in the rumen fluid. Further the highest level of intake caused a considerable diurnal variation in the pH and the concentration of total VFA, and increased the variation in the molar composition of the VFA mixture.Three feeding intervals ranging from 8 to 16 hrs., with hay administered at maintenance level, caused no changes in the fermentation pattern.Typical variations in the concentrations of ammonia and valeric acid as related to time after feeding were demonstrated, but the concentrations of the branched-chain fatty acids in the rumen fluid were found to be quite constant.It may be concluded that a representative mean value of the parameters measured, except for ammonia and valeric acid, may be based on relatively few samples when feed intake does not exceed maintenance level, whereas sampling every hour is required at higher feeding levels.     

饲粮不同NFC/NDF对肉用绵羊瘤胃pH、氨态氮和挥发性脂肪酸的影响

本试验旨在研究饲粮不同非纤维性碳水化合物/中性洗涤纤维(NFC/NDF)对肉用绵羊瘤胃pH、氨态氮和挥发性脂肪酸的影响.选用(47.21±1.01)kg安装有瘤胃瘘管的杜泊羊(♂)×小尾寒羊(♀)杂交1代肉用公羊12只,采用12×4不完全拉丁方设计,试验分4期进行,每期16 d,分别饲喂NFC/NDF为0.25、0.34、0.36、0.52、0.60、0.80、0.87、1.13、1.30、1.58、2.17和2.49的12种饲粮.结果表明:随着NFC/NDF的增加,试验羊瘤胃pH极显著线性降低(P＜0.01),氨态氮浓度极显著线性增加(P＜0.01),瘤胃总挥发性脂肪酸及丁酸比例呈显著三次曲线变化(P＜0.05),总挥发性脂肪酸中的丙酸、戊酸和异戊酸比例极显著线性增加(P＜0.01),乙酸比例和乙酸/丙酸极显著线性降低(P＜0.01).由此可见,饲粮NFC/NDF对瘤胃pH、氨态氮和挥发性脂肪酸具有显著影响.     

Relationship between the volatile fatty acids (VFA) in the rumen and nitrogen secretion into isolated sheep's rumen]

Two sheep with a ruminal fistula and an isolated small rumen were studied for the secretion of ammonia nitrogen, urea nitrogen, and amino nitrogen into the isolated rumen at different levels of volatile fatty acids (VFA) (50, 133-97, and 97-66 M Mol 1(-1)) in the rumen. The VFA level in the rumen was found to exert a great influence on the quantitative secretion of endogenous nitrogen from the blood through the rumen wall into rumen content. When the VFA level in the rumen was increased by administration of a single dose of acetic, propionic, and butyric acid, the secretion of ammonia nitrogen and amino nitrogen abruptly dropped and the secretion of urea into the isolated rumen slightly increased. The over-all amount of nitrogen (NH3-N + urea-N + amino-N) that had passed into the isolated rumen in the course of an hour showed a highly significant correlation with the passage of nitrogen in the form of ammonia and amino nitrogen and was greatest before the application of VFA to the rumen, i.e. at the level of 50 m mol 1-1. Of the metabolites under study, which were passing to the isolated rumen, amino nitrogen shared the greatest proportion (45.38-46.54%). When the VFA level in the rumen was raised, the proportion of ammonia secreted to the isolated rumen decreased and the proportion of urea in the total amount of nitrogen increased.     

克伦特罗对绵羊肝脏挥发性脂肪酸和糖代谢的影响

在 4头门静脉、肝静脉、颈静脉、肠系膜静脉和股动脉上安装血管导管的绵羊中研究了克伦特罗 (CL ,0 8mg/kgBW ,肠系膜静脉给药每天 2次 ,连续 5d)对其肝脏物质代谢的影响。结果表明 :CL可增加绵羊肝脏中的VFA流量 ,其中门静脉处乙酸、丙酸和丁酸的流量分别较对照期增加 19 4 9% (P <0 .0 1)、2 0 2 % (P >0 .0 5 )和4 5 5 % (P >0 .0 5 ) ,而肝静脉处VFA流量两期水平接近。CL也提高肝脏中葡萄糖的异生作用 ,在肝静脉处血中葡萄糖流量上升了 2 5 96 % (P <0 .0 1)。门静脉处血中葡萄糖循环水平也相应提高。此外在CL作用下肝静脉处胰岛素水平也较对照期有所下降。提示CL可增加进入绵羊肝脏中VFA的流量并促进肝脏对VFA的吸收和利用。通过降低胰岛素水平或对肝脏的直接作用CL还可增加绵羊血中葡萄糖的水平     

Production of acids from inulin by a mixed culture of rumen microorganisms

The production of volatile fatty acids (VFA) and lactic acid from inulin (plant fructan with 2-1 bonds) in in vitro rumen fermentations was followed. The experiments were performed with inocula from wethers receiving two rations, with two pH regimes and using as inocula either whole rumen contents or the corresponding rumen fluid. The following results were obtained: The VFA production was higher when using inocula from hay and concentrate fed wethers. In contrast to this, the lactic acid production was higher when using inocula from hay fed wethers. The VFA production tends to be higher in a weakly acid medium than in a neutral medium. Acetate-to-propionate molar ratio was lower at lower pH. The amounts and composition of the VFA were not different when using both types of inocula. Thus, we believe that micro-organisms colonising plant fibres obviously do not play an important role in inulin splitting.     

Feeding animal fats to sheep.

In an experiment lasting 7 weeks, 18% of the calculated energy requirement of 5 nonpregnant ewes was met by giving natural fats of animal origin mixed in the ration (at a level of 6.6%). Changes in certain blood and blood plasma parameters of lipid and energy metabolism were monitored at 5 time-points during the experiment. Samples of rumen fluid were taken three times for determining the concentrations of volatile fatty acids (VFA). Rumen fermentation was studied by in sacco method. Total lipid (TL) content of the liver and fatty acid composition of the liver tissue and subcutaneous adipose tissue (from the tailhead) were analyzed at the beginning and at the end of the experiment. At the concentration used in this experiment, fat supplementation caused neither digestive disturbances nor any other adverse changes in the animals' health status. It did, however, exert a significant influence on blood plasma lipid composition. TL and total cholesterol (TCh) concentration increased and blood glucose level decreased. A rise in triglyceride (TG) content was accompanied by a drop in free fatty acid (FFA) concentration. The in sacco experiments and volatile fatty acid (VFA) levels in the rumen fluid suggested an impaired crude fibre digestion in the rumen. At the same time, fat supplementation enhanced rumen proteolysis. The TL content of liver samples did not exceed the physiological limit. The liver biopsy samples had decreased myristic acid and increased stearic and oleic acid concentrations. No change occurred in the fatty acid composition of the fat depots.     

Using a novel macro in vitro technique to estimate differences in absorption rates of volatile fatty acids in the rumen

A novel macro in vitro system was used to test the theory that rumen proportions of acetate, propionate and butyrate are not representative of their respective net production rates. Whole rumen content (10–16 kg) from two cows was mixed with a bicarbonate buffer and incubated separately in two 40‐l in vitro vessels for 3 h. A total of six experimental periods were used. In this study, a total of six cows were used and fed 1/8 of the daily ration by hand every 3 h. To obtain differences in rumen volatile fatty acids (VFA) composition, 1 l of acetate (416 mm ), propionate (108 mm ), butyrate (79 mm ), lactic acid (300 mm ) or nothing was infused during 24 h into the rumen before collection of representative samples of rumen contents. Infusions of acids were then continued during the in vitro incubations in exact proportion to the digesta removed from the rumen. In Periods 1 and 2, the cows were alternatively infused with acetate or nothing. In Periods 3 and 4, the infusions consisted of propionate or butyrate and in Periods 5 and 6 of lactate or nothing. Nine liquid samples were obtained between 3 and 180 min after the start of incubation and analysed for concentrations of VFA. Changes in proportions of individual VFA were estimated by linear regression. No differences in VFA proportions were observed in the absence of infusion (p > 0.5) over time, but when individual VFA were infused, their respective proportions increased. This was interpreted as the result of a decreased in vitro fermentation rate of digesta substrates compared with that in the rumen. Lactate infusion increased butyrate proportion in vitro. It is concluded that this study could not provide any evidence that ruminal VFA proportions are unrepresentative of the proportions of net production.