Reducing Rumen Methane Emissions through Strengthening Acetogens Pathway

产乙酸菌是一类形态、营养和生理特征极其多样化的厌氧微生物.以二氧化碳为终端电子受体的氢依赖性乙酸生成过程与甲烷生成过程相比,热力学上处于劣势.产乙酸菌的代谢多样性使其广泛存在于自然界和动物肠道内.白蚁、鸵鸟和袋鼠等物种胃肠道内的产乙酸菌利用氢生成的乙酸可以满足动物自身7％～33％的能量需要.瘤胃内也有产乙酸菌定植,是否可以通过强化瘤胃内产乙酸菌的代谢途径,减少反刍动物甲烷排放.为了回答这一问题,本文就瘤胃中产乙酸菌的菌群结构、产乙酸菌与产甲烷菌的竞争关系、产乙酸菌的利用战略进行了探讨.     

瘤胃甲烷生成过程中微生物之间的相互关系

反刍动物瘤胃含有甲烷菌,是主要的甲烷(methane,CH4)排放源,甲烷菌利用饲料发酵过程中生成的氢和CO2作为主要的电子受体和供体通过还原反应生成甲烷,在瘤胃功能性生态生境(niche)中发挥重要作用.除甲烷菌以外,其他瘤胃微生物也影响甲烷产量.瘤胃微生物总体来说可分为产氢微生物(hydrogenogens)和耗氢...     

瘤胃产甲烷菌与其他微生物间的氢传递及其调控研究进展

在反刍动物瘤胃中产甲烷菌生成甲烷既造成能量的浪费又产生大量温室气体,因此减少瘤胃甲烷生成与排放是提升生产效率与维持可持续发展的要求。瘤胃内的产甲烷菌通过共生、黏附和伴生模式,分别从原虫、细菌和真菌中摄取氢,保证氢营养型甲烷生成途径的顺利进行。抑杀原虫和产氢细菌、竞争性结合氢和阻断氢生成甲烷是基于氢调控抑制甲烷生成的途径。由于瘤胃微生物的冗余和互作,降甲烷的同时,瘤胃中饲料消化可能受到抑制,且单一的氢调控往往会诱发瘤胃的适应,瘤胃的降甲烷效果仅能短时间维持。为此,需从瘤胃微生物整体出发,通过多种氢调控机制的添加剂联用及间歇饲喂、幼龄反刍动物瘤胃早期调控、甲烷生成途径关键酶调控等的综合应用,实现更优的甲烷减排。     

探讨影响奶牛瘤胃甲烷产生的因素

奶牛瘤胃产生并释放的甲烷,大约占饲料总能损失的5%~9%,一头奶牛每年产大约60~160kg甲烷。瘤胃中的甲烷产生菌通过获得氢把CO_2还原成CH_4,瘤胃中氢浓度受化学极性基团和饲料中的植物化学活性成份的调节,宿主动物和共生微生物维持瘤胃pH在6~7的范围,瘤胃中的代谢氢处理是由有效的瘤胃生态系统的适应和调节。该综述将探讨涉及这些生化过程的化学竞争和影响瘤胃细菌产生甲烷的因素。     

反刍动物瘤胃优势产甲烷菌菌群结构及多样性研究进展北大核心CSCD

甲烷是反刍动物瘤胃产甲烷菌分解饲粮有机物的最终产物,它不仅是一种造成极端气候变化的重要温室气体,而且也难以被动物利用,造成能量损失和养殖效率降低。瘤胃产甲烷菌还原二氧化碳生成甲烷的过程受到动物品种、遗传背景、生理阶段以及地理背景等诸多因素的影响。本文重点总结了国内外典型反刍动物瘤胃内产甲烷菌菌群的组成和多样性特征,以期明确瘤胃甲烷排放机理,为进一步研究产甲烷菌的基因功能和代谢途径以及探索反刍动物瘤胃甲烷减排和调控机制提供参考。     

瘤胃素添加剂(Rumonsin—60)对山羊补饲育肥试验

反雏家畜瘤胃内碳水化合物的降解过程,受多种因素的影响,当其单糖降解为丙酸时,可向动物提供较多的有效能,而降解为乙酸时,可生成甲烷并以暖气形式排出体外,其中的能量不能被动物利用,从而降低饲料利用率。据报导,瘤胃素(Rumonsin或Mononsin)可调节瘤胃发酵,提高丙酸比例,使饲料利用率提高10％左右。目前美国大多数肥育肉牛和部份放牧肉牛用瘤胃素,对肉牛增长起到很大     

瘤胃素作为短期育肥的添加剂效果较好

<正> 反刍家畜瘤胃内碳水化合物的降解过程,受多种因素的影响,当其单糖降解为丙酸时,可向动物提供较多的有效能,而降解为乙酸时,可生成甲烷并以嗳气形式排出体外,其中的能量不能被动物利用,从而降低饲料利用率,据报道,瘤胃素(Rumensin或Monensin)可调节瘤胃发酵,提高丙酸     

瘤胃纤毛虫对甲烷菌和甲烷产量的影响

反刍动物体内甲烷的产生是瘤胃内发酵能量损失的主要原因 ,减少甲烷的产生对提高饲料能量利用率和改善环境有重要意义。为调节和控制瘤胃内甲烷产量 ,需要对甲烷产生的代谢机制进行探讨。研究表明 ,甲烷菌与瘤胃纤毛虫关系密切 ,本文从甲烷菌和纤毛虫两者的关系入手对瘤胃甲烷的产生进行探讨     

牛至精油缓解反刍动物瘤胃甲烷排放的研究进展

反刍动物温室气体的排放量占畜禽温室气体总排放量的80%,甲烷作为瘤胃微生物代谢的副产物，不仅对环境造成严重危害还降低了反刍动物的饲料能量利用率。植物提取物凭借其调节瘤胃微生物群落的功效在甲烷减排领域成为研究热点之一。牛至精油是从牛至中提取的一种含多种生物活性物质的植物提取物，以麝香草酚和香芹酚为主效因子，具有改善瘤胃内环境、改变瘤胃微生物组成、调控瘤胃发酵等生物学功能，在反刍动物养殖领域的应用前景十分广阔。关于牛至精油降低甲烷的作用效果已在多种动物上进行研究，结果表明牛至精油能通过调节瘤胃微生物及其代谢来降低瘤胃甲烷排放，但对其作用机制的研究还不够深入。作者以反刍动物为对象，对牛至精油通过调节瘤胃中细菌、古菌以及原虫的丰度和组成，调控瘤胃代谢，抑制二氧化碳还原途径和乙酸发酵途径，达到改善甲烷排放的作用机制进行综述，以期为牛至精油在饲料中的应用提供参考。     

大蒜油对体外瘤胃发酵、甲烷生成和微生物区系的影响

本试验旨在通过体外培养法研究大蒜油和脱臭大蒜油对瘤胃发酵、甲烷生成和微生物区系的影响.在体外培养过程中用压力读取式法(RPT系统)测定产气量,利用气相色谱仪测定甲烷产量.培养24 h后,测定挥发性脂肪酸、pH、氨态氮浓度,并用实时荧光定量PCR测定瘤胃微生物区系.研究发现,与对照组相比,添加大蒜油极显著降低甲烷产量(P<0.01),显著降低乙酸摩尔百分比和氨态氮浓度(P<0.05),显著提高丙酸摩尔百分比(P<0.05),对产气量和总挥发性脂肪酸含量也有显著地抑制作用(P<0.05),但抑制程度不如大蒜油对甲烷产量的抑制程度.添加脱臭大蒜油对甲烷产生也有一定作用,但效果不显著(P>0.05).添加大蒜油和脱臭大蒜油后甲烷菌和原虫含量极显著降低(P<0.01),且大蒜油的抑制作用强于脱臭大蒜油(P<0.01).试验结果表明.适宜浓度的大蒜油可以改变瘤胃发酵类型,增加丙酸摩尔百分比,显著抑制甲烷生成而不影响消化,这种改变与瘤胃微生物区系的变化密切相关;此外,大蒜油的作用效果明显强于脱臭大蒜油.     

Na(+)-dependent transport of D-xylose by bovine intestinal brush border membrane vesicles (BBMV) is inhibited by various pentoses and hexoses

To detect whether pentoses and hexoses occurring in rumen bacteria or in hemicellulose ingested with feed and partly released in the small intestine have an affinity for the Na(+)-dependent glucose transporter of the bovine intestinal brush border membrane (BBM), we investigated whether these monosaccharides inhibit Na(+)-dependent transport of 14C-labelled D-xylose across the BBM using brush border membrane vesicles (BBMV) isolated from the mid-jejunum of cows. We used D-xylose as the transport substrate, because it has a low affinity for the Na(+)-dependent glucose transporter and thus its uptake into BBMV is more efficiently competitively inhibited by other sugars than that of D-glucose. D-Ribose, D-mannose and L-rhamnose occurring in rumen bacteria significantly inhibited Na(+)-dependent uptake of D-xylose into BBMV, but their inhibitory effect was less than that of D-glucose, D-xylose and phlorizin. This also applied to L-arabinose (and D-arabinose), which is, like D-xylose and D-galactose, a constituent of hemicellulose, and to 2-deoxy-D-glucose. Of all monosaccharides tested, only D-fructose did not affect Na(+)-dependent D-xylose transport. It is concluded that some pentoses and hexoses occurring in rumen bacteria (D-ribose, D-mannose and L-rhamnose) or hemicellulose (L-arabinose and D-xylose) have a low affinity for the Na(+)-dependent glucose transporter of the bovine BBM and may therefore be absorbed from the jejunum when released in the small intestine.     

Sulphur availability and microbial fermentation in the fauna-free rumen.

The concentration of H2S and rate of feed digestion, VFA and methane production in the rumen were measured in sulphur deficient (-S) and S supplemented (+S) sheep while fauna-free (-P) and after refaunation (+P). The concentration of rumen H2S was increased by S supplementation but was not affected by the presence of protozoa. When fauna-free, -S sheep had reduced rates of feed digestion (30 v 48%/d), acetate synthesis (35 v 115 g/d) and methane synthesis (0.4 v 7.4 g C/d) compared to +S sheep and up to 36% (v/v) of total rumen gas was H2. When these sheep were given a single dose of 8.8 g Na2SO4, the proportion of methane increased and the proportion of H2 in rumen gas decreased. After refaunation of sheep, their rates of feed digestion, VFA production and methane production were higher and were not affected by the level of S. From this differential response to S deficiency by -P and +P sheep, it is concluded rumen protozoa increase the availability of S to other rumen microbes. This is probably because they degrade protein through to peptides and amino acids.     

Effect of dietary lactic acid on rumen lactate metabolism and blood acid-base status of lambs switched from low to high concentrate diets.

Two experiments were conducted with ruminally fistulated wether lambs to determine the effect of lactic acid addition to a hay diet on rumen lactate metabolism, blood acid-base status and subsequent adaptation to a high concentrate diet. In Exp. 1, lambs were fed mature brome hay (H), H plus 5% (w/w) D,L lactic acid (H5L) or H plus 10% lactic acid (H10L) (three lambs per treatment) for 14 days (phase I) then switched to a 90% concentrate diet for 2 days (phase II). In Exp. 2, lambs were fed alfalfa-brome hay (H) (six lambs), H plus 2.5% lactic acid (H2.5L) (six lambs) or H plus 5% lactic acid (H5L) (four lambs) during phase I, then switched to a 70% concentrate diet (3 days) followed by a 90% concentrate diet (10 days) (phase II). During both experiments rumen fluid samples were taken periodically for pH and lactate analyses and in vitro L- or D-lactate disappearance (IVLD) studies. Blood samples were taken to measure acid-base status, serum lactate, and serum calcium, magnesium and phosphorus. Dietary lactic acid enhanced IVLD during phase I of both experiments. L and D isomer IVLD rates were similar and followed zero-order kinetics. In Exp. 2, IVLD increased rapidly during phase II in response to increased concentrate level in the diet; the enhanced rates of H2.5L and H5L lambs were sustained for the first 3 days of phase II. Blood data from both experiments indicated a deleterious effect of dietary lactic acid on blood acid-base balance; however, this treatment effect was not manifested in any symptoms of acute acidosis. There was a decrease (P less than .05) in serum calcium during phase II of both experiments. In Experiment 1, serum calcium increased linearly (P less than .05) in response to dietary lactic acid level. In Exp. 1, rumen fluid total lactate and L-lactate were lower (P less than .05) for H5L vs H lambs during phase II. However, all lambs in Exp. 1 experienced acute acidosis; four of the nine lambs subsequently died. There was evidence of acidosis in Exp. 2, but there were no clear treatment effects during phase II on rumen fluid pH or lactate, or feed intake. All lambs adapted to the high concentrate diets as evidenced by rumen lactate levels and feed intakes. In both experiments, the proportion of L-lactate in rumen fluid decreased from almost 100 to about 50% of total lactate by the end of phase II.     

Effects of dietary nitrogen level and ileal antibiotic administration on digestion and passage rate in beef heifers. II. High-forage diets

Four beef heifers (258 kg), fitted with ruminal, duodenal and ileal cannulae (T-type), were fed a high-forage diet with a low (L) or high (H) level of N (1.44 and 2%, respectively), and received daily doses of either antibiotics (A; 2 g neomycin sulfate and .25 g of bacitracin) or saline (S) into the ileum in a 4 X 4 Latin-square experiment. Passage of nonammonia-N to the duodenum represented 128, 142, 92 and 104% of N intake for LS, LA, HS and HA treatments, respectively, indicating that administration of antibiotics into the ileum tended to increase the output of N from the rumen. Digestion of organic matter, acid detergent fiber and starch in the rumen tended to be lower in animals receiving antibiotics in the terminal ileum. Administration of antibiotics into the ileum tended to increase ruminal ammonia-N (NH3-N) concentration with the H diet, but to decrease ruminal NH3-N with the L diet. Particle passage rate from the rumen, estimated from marker concentrations in feces, was negatively related to ruminal organic matter digestion (r = -.52; P less than .03). Ileal antibiotic infusion tended to slow passage of fluid from the rumen and hindgut, but to increase volume of digesta in the hindgut.     

Effects of protozoa on methane production in rumen and hindgut of calves around time of weaning.

Effects of the presence or absence of ciliate protozoa on methanogenesis in the rumen and hindgut were investigated in young calves during a 7-week period. Ten Holstein calves, aged 7 days, were divided in two groups (n = 5) and fed an increasing amount of a commercial milk replacer and small amounts of a calves starter. One group was inoculated with ciliate fauna on two occasions, week 5 and 6, while the second remained ciliate-free. The absence of protozoa in the rumen decreased rumen empty weight (-23%, P < 0.01), and rumen pool size of N (-36%, P < 0.01) and crude fat (-37%, P < 0.05). Rumen bacteria of non-faunated calves contained a higher proportion of total amino acid-N per 16 g N (+3%, P < 0.01) and D-alanine-N per 16 g N (+13%, P < 0.05) compared to faunated calves. Further results contain a reference for a higher bacterial mass in the ciliate-free rumen with an increased number of bacteria adherent to rumen mucosa. The CH4 production in the rumen increased exponentially with the increase in protozoa population size (R2 = 0.68). In presence of 46 x 10(4) protozoa per ml rumen fluid, the in vitro CH4 production of rumen fluid per mol total VFA was about 34% higher in faunated than in non-faunated calves (P < 0.001). Hydrogen (2H) recovery of rumen fermentation was positively correlated (R2 = 0.55) to the CH4 production rate. Methanogens were attached on rumen mucosa. Methanogenesis, induced by rumen mucosa attached bacteria, was stimulated by ruminal protozoa. In the absence of protozoa in the rumen, the acetate-propionate ratio and butyrate proportion of VFA were reduced. In vivo, in the absence of protozoa not only the whole animal CH4 production (-30%, P < 0.05) but also the digestibility of carbohydrates (-4%, P < 0.05) was reduced. Thereby no difference was observed in the intake of ME per kg DM between the groups. In conclusion, the methanogenesis in the rumen, but not in hindgut, is associated with the development of the ruminal protozoa population. The level of methanogenesis (mol/mol VFA) in the hindgut amounts to 20% of the ruminal methanogenesis.     

The Influence of Tallow on Rumen Metabolism,Microbial Biomass Synthesis and Fatty Acid Composition of Bacteria and Protozoa

Abstract

Rumen metabolism, microbial biomass synthesis and microbial long chain fatty acid composition were studied in lactating cows fed at two levels of dry matter intake (L, 8.6 kg DM and H, 12.6 kg DM) with 0, 4 and 6% added tallow at the low feed level (L0, L4 and L6) and 0, 2, 4 and 6% at the high feed level (H0, H2, H4 and H6).

Fibre digestibility was not significantly affected by tallow addition. Increasing tallow level in the diet decreased the total VFA concentration, the ratio of acetic acid to propionic acid and the ammonia concentration in the rumen. Crude fat and fatty acid content in bacterial and protozoal dry matter increased with increased tallow level, especially due to an increase in fatty acids originating from the feeds. Microbial synthesis in the rumen and flow of amino acids to the duodenum was highest for medium fat intake at the high feed level.     

Effect of the magnitude of the decrease of rumen pH on rumen fermentation in a dual-flow continuous culture system

The negative effect of pH on rumen microbial fermentation has been associated with the total amount of time that pH is below a certain threshold. However, not only the time, but also the magnitude of the pH reduction, is important. Eight 1,325-mL dual-flow continuous culture fermenters were used in 2 replicated periods to determine the effect of the magnitude of pH reduction (5.6 vs. 5.1) during 4 h/d on rumen microbial fermentation. Fermenters were maintained at a constant temperature (38.5 degrees C) and fed 97 g/d of a 60:40 forage:concentrate diet (19.2% CP, 29.0% NDF, and 18.2% ADF, DM basis), and the solid and liquid dilution rates were controlled at 5.0 and 10.0%/h, respectively. Treatments were a constant pH 6.4 (H), 4 h/d at pH 5.6 (L), 4 h/d at pH 5.1 (VL), and 2 h/d at pH 5.1 and 2 h/d at pH 7.1 (HL). Relative to H, L did not affect OM and NDF digestion, the VFA profile, NH(3)-N concentration, CP degradation, or the flow of dietary N. In contrast, VL tended (P < 0.10) to reduce true OM digestion, reduce the NDF digestibility and the acetate and branch-chained VFA proportions, and increase the propionate proportion. Compared with H, VL reduced the CP degradation and the flow of dietary N. Relative to H, treatment HL did not affect OM and NDF digestibility, the acetate proportion, CP degradation, or the flow of dietary N but increased the propionate proportion and decreased the branch-chained VFA proportion and NH(3)-N concentration. There were no differences among treatments in the efficiency of microbial protein synthesis, the flow of bacterial N, or the flow of essential and nonessential AA. In summary, fermentation was not affected by either 4 h/d at pH 5.6 or fluctuating pH between 5.1 (2 h/d) and 7.1 (2 h/d), but when pH was at 5.1 for 4 h/d, rumen microbial fermentation was modified, suggesting that effects of low pH on rumen microbial fermentation are dependent on the magnitude of the pH decrease.     

Effects of heat exposure on nutrient digestibility, rumen contraction and hormone secretion in goats

The present study investigated changes in nutrient digestibility, rumen fermentation, behavior and hormone (growth hormone (GH), insulin and insulin‐like growth factor‐1 (IGF‐1)) secretion among goats (three male goats) in a hot environment (H, 35 ± 1.2°C; relative humidity (RH), 80 ± 7.2%; 13 days), in a thermoneutral environment (T, 20 ± 0.6°C; RH, 80 ± 3.4%; 20 days), and in a thermoneutral environment accompanied by the same restricted diet as provided in the hot environment (TR, 20 ± 0.6°C; RH, 80 ± 3.4%; 20 days). The following results were obtained: rectal temperature and water intake were higher in the H treatment than in the T treatment or TR treatment, while hay consumption was lower. Crude protein, neutral detergent fiber and acid detergent fiber digestibility was highest in H treatment. The concentrations of acetic acid and butyric acid in the rumen was also highest in the H treatment. Time spent eating in the H treatment was also the highest, followed in order by T treatment and TR treatment. Ruminating time was lower in H treatment than in T treatment or TR treatment, and reposing time was highest in the TR treatment. When eating and ruminating, the amplitude values of the rumen contraction were lowest in the H treatment, as was the frequency of rumen contraction. Excretion of plastic particles was faster in T treatment and TR treatment than H treatment. Heat exposure was associated with world lowered concentrations of total volatile fatty acids and acetic acid in plasma. The plasma glucose concentration was highest in the T treatment, followed in order by TR treatment and H treatment. The plasma GH concentration was lowest in the H treatment, while the plasma insulin was highest in the H treatment. The IGF‐1 concentration was highest in the H treatment, followed in order by T treatment and TR treatment. In conclusion, heat exposure in goats decreased feed intake and rumen contraction, but increased digestibility. However, when goats in a thermoneutral environment received the same restricted feeding as they received in the hot environment, digestibility increased without a change in rumen contraction. Between the H treatment and TR treatment, the changes in digestibility were accomplished by coordinate changes in hormone secretion in order to maintain body homeostasis.     

日粮能量水平对湖羊瘤胃发酵特性和微生物组成的影响

本试验旨在探究不同能量水平对湖羊瘤胃发酵特性和微生物组成的影响。选取湖羊公羊48只（体重为（17.77±1.15） kg）随机分为2组：1）对照组（C组）,代谢能ME=8.83 MJ·kg^-1;2）高能组（H组）,ME=10.84 MJ·kg^-1。每组6个重复,每个重复4只羊。试验期105 d,其中预试期15 d,正试期90 d。试验结束后,采集瘤胃液测定瘤胃发酵参数,同时对微生物细菌V3-V4区进行16S rRNA高通量测序以检测瘤胃微生物组成。结果显示：1） H组和C组在瘤胃pH、总挥发性脂肪酸、乙酸、丙酸、异丁酸、丁酸、异戊酸、戊酸及乙丙比、氨态氮和微生物菌体蛋白浓度差异均不显著（P>0.05）;2）物种多样性结果显示,H组的Chao 1、Observed species、PD whole tree和Shannon指数均显著低于C组（P<0.05）;3）物种注释发现,拟杆菌门（Bacteroidetes）和厚壁菌门（Firmicutes）占比最高,但两者的相对丰度在H组和C组间差异均不显著（P>0.05）,H组的瘤胃球菌属（Ruminococcus）和厌氧弧菌属（Anaerovibrio）相对丰度均显著高于C组（P<0.05）。在本试验条件下,提高日粮能量水平对瘤胃发酵特性影响不显著,但是会降低瘤胃微生物的丰富度和均匀度,并改变部分菌属的相对丰度。