Magnesium requirement of some of the principal rumen cellulolytic bacteria

Information available on the role of Mg for growth and cellulose degradation by rumen bacteria is both limited and inconsistent. In this study, the Mg requirements for two strains each of the cellulolytic rumen species Fibrobacter succinogenes (A3c and S85), Ruminococcus albus (7 and 8) and Ruminococcus flavefaciens (B34b and C94) were investigated. Maximum growth, rate of growth and lag time were all measured using a complete factorial design, 2(3)×6; factors were: strains (2), within species (3) and Mg concentrations (6). R. flavefaciens was the only species that did not grow when Mg was singly deleted from the media, and both strains exhibited a linear growth response to increasing Mg concentrations (P<0.001). The requirement for R. flavefaciens B34b was estimated as 0.54 mM; whereas the requirement for R. flavefaciens C94 was >0.82 as there was no plateau in growth. Although not an absolute requirement for growth, strains of the two other species of cellulolytic bacteria all responded to increasing Mg concentrations. For F. succinogenes S85, R. albus 7 and R. albus 8, their requirement estimated from maximum growth was 0.56, 0.52 and 0.51, respectively. A requirement for F. succinogenes A3c could not be calculated because there was no solution for contrasts. Whether R. flavefaciens had a Mg requirement for cellulose degradation was determined in NH₃-free cellulose media, using a 2×4 factorial design, 2 strains and 4 treatments. Both strains of R. flavefaciens were found to have an absolute Mg requirement for cellulose degradation. Based on reported concentrations of Mg in the rumen, 1.0 to 10.1 mM, it seems unlikely that an in vivo deficiency of this element would occur.     

Quantification by real-time PCR of cellulolytic bacteria in the rumen of sheep after supplementation of a forage diet with readily fermentable carbohydrates: effect of a yeast additive

AIM: To examine the effect of concentrate and yeast additive on the number of cellulolytic bacteria in the rumen of sheep. METHODS AND RESULTS: Fibrobacter succinogenes, Ruminococcus albus and Ruminococcus flavefaciens were quantified using real-time PCR (targeting 16S rDNA) in parallel to cellulolytic flora enumeration with cultural techniques. Whatever the conditions tested, R. flavefaciens was slightly more abundant than F. succinogenes, with both species outnumbering R. albus. Before feeding, the shift from hay to hay plus concentrate diet had no effect on rumen pH and on the number of the three specie; while after feeding, the concentrate-supplemented diet induced a decrease (-1 log) of the number of the three species concomitant with the rumen acidification. Overall, the presence of the live yeast resulted in a significant increase (two- to fourfold) of the Ruminococci. CONCLUSION: The use of real-time PCR allowed us to show changes in the number of cellulolytic bacterial species in vivo in response to diet shift and additives that could not be as easily evidenced by classical microbial methods. SIGNIFICANCE AND IMPACT OF THE STUDY: This study contributes to the understanding of the negative impact of readily fermentable carbohydrates on rumen cellulolysis and the beneficial effect of yeast on rumen fermentation.     

Branched-chain volatile fatty acids and folic acid accelerated the growth of Holstein dairy calves by stimulating nutrient digestion and rumen metabolism

The combined addition of branched-chain volatile fatty acids (BCVFAs) and folic acid (FA) could improve growth performance and nutrient utilization by stimulating ruminal microbial growth and enzyme activity. This study was conducted to evaluate the effects of BCVFA and FA addition on growth performance, ruminal fermentation, nutrient digestibility, microbial enzyme activity, microflora and excretion of urinary purine derivatives (PDs) in calves. Thirty-six Chinese Holstein weaned calves (60 ± 5.4 days of age and 107 ± 4.7 kg of BW) were assigned to one of four groups in a randomized block design. Treatments were control (without additives), FA (with 10 mg FA/kg dietary DM), BCVFA (with 5 g BCVFA/kg dietary DM) and the combined addition of FA and BCVFA (10 mg/kg DM of FA and 5 g/kg DM of BCVFA). Supplements were hand-mixed into the top one-third of total mixed ration. Dietary concentrate to maize silage ratio was 50 : 50 on a DM basis. Dietary BCVFA or FA addition did not affect dry matter intake but increased average daily gain (ADG) and feed conversion efficiency. Ruminal pH and ammonia N were lower, and total volatile fatty acids (VFAs) concentration was higher for BCVFA or FA addition than for control. Dietary BCVFA or FA addition did not affect acetate proportion but decreased propionate proportion and increased acetate to propionate ratio. Total tract digestibility of DM, organic matter, CP and NDF was higher for BCVFA or FA addition than for control. Dietary BCVFA or FA addition increased activity of carboxymethyl cellulase and cellobiase, population of total bacteria, fungi, Ruminococcus albus, R. flavefaciens, Fibrobacter succinogenes and Prevotella ruminicola as well as total PD excretion. Ruminal xylanase, pectinase and protease activity and Butyrivibrio fibrisolvens population were increased by BCVFA addition, whereas population of protozoa and methanogens was increased by FA addition. The BCVFA × FA interaction was significant for acetate to propionate ratio, cellobiase activity and total PD excretion, and these variables increased more with FA addition in diet without BCVFA than in diet with BCVFA. The data indicated that supplementation with BCVFA or FA increased ADG, nutrient digestibility, ruminal total VFA concentration and microbial protein synthesis by stimulating ruminal microbial growth and enzyme activity in calves.     

PCR-DGGE analysis reveals a distinct diversity in the bacterial population attached to the rumen epithelium

Bacteria attached to the rumen epithelium (or epimural community) are not well characterised and their role in rumen functioning is not totally understood. There is just one published report of a clone library from one cow that suggests that this epimural community differs from the bacteria associated with the rumen digestive contents. However, this time-consuming approach is not adapted for examining microbial population changes in groups of animals. In in vivo studies, when samples from several animals have to be analysed simultaneously, a simpler technique has to be used. In this study, a genetic fingerprinting technique, polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE), was used to characterise the structure of the bacterial population attached to the rumen epithelium. This community was compared with that present in the solid and liquid phases of rumen content under two contrasting diets. Rumen samples were obtained from four forage-fed and four high-concentrate-fed (80 : 20, wheat grain : hay) 5-month-old lambs. After slaughter, samples from five epithelial sites and the solid and liquid digesta phases were taken for DNA extraction and analysis. Bacterial communities were profiled by PCR-DGGE using bacterial-specific 16S rDNA primers. Analysis of the fingerprint revealed that the epithelial community differed from those of rumen content in both diets. As expected, the nature of the feed influenced the bacterial communities from the solid and liquid rumen phases but no diet effect was observed in the rumen epithelial profiles suggesting a strong host effect on this bacterial population. Additionally, no differences were observed among the five epithelial sampling sites taken from each animal. The profile of the bacterial population attached to the rumen epithelium presented a high inter-animal variation, whether this difference has an influence in the function of this community remains to be determined.     

Characterization of the dynamics of initial bacterial colonization of nonconserved forage in the bovine rumen

Microbial colonization is central to ruminal degradation of dietary material yet little is known about the dynamics of this process. The aim of this study was to characterize the initial stages of bacterial colonization of forage, and to assess the impact that different postsample processing and analysis methods had on the results obtained. Bacterial 16S rRNA gene-based analysis of damaged, nonconserved perennial ryegrass, incubated in sacco in the bovine rumen, required the development and validation of new quantitative PCR and denaturing gradient gel electrophoresis (DGGE) primers. Analysis with previously available primer sets was compromised due to dominant amplification of forage-derived chloroplast 16S rRNA genes. DGGE analysis of incubated samples demonstrated that a diverse and consistent population of ruminal bacteria colonized rapidly. Postsampling methodologies did not affect overall population profiles whereas the washing method appeared to influence bacterial numbers. However, regardless of processing methodology, bacterial numbers increased rapidly within 5 min, stabilizing after 15 min of incubation. These findings reveal for the first time the dynamics of bacterial colonization of forage within the rumen.     

Effect of sulfur supplements on cellulolytic rumen micro-organisms and microbial protein synthesis in cattle fed a high fibre diet

AIM: To examine the effect of sulfur-containing compounds on the growth of anaerobic rumen fungi and the fibrolytic rumen bacteria Ruminococcus albus, Ruminococcus flavefaciens and Fibrobacter succinogenes in pure culture and within the cattle rumen. METHODS AND RESULTS: The effect of two reduced sulfur compounds, 3-mercaptopropionic acid (MPA) or 3-mercapto-1-propanesulfonic acid as the sole S source on growth of pure fibroyltic fungal and bacterial cultures showed that these compounds were capable of sustaining growth. An in vivo trial was then conducted to determine the effect of sulfur supplements (MPA and sodium sulfate) on microbial population dynamics in cattle fed the roughage Dichanthium aristatum. Real-time PCR showed significant increases in fibrolytic bacterial and fungal populations when cattle were supplemented with these compounds. Sulfate supplementation leads to an increase in dry matter intake without a change in whole tract dry matter digestibility. CONCLUSIONS: Supplementation of low S-containing diets with either sodium sulfate or MPA stimulates microbial growth with an increase in rumen microbial protein supply to the animal. SIGNIFICANCE AND IMPACT OF THE STUDY: Through the use of real-time PCR monitoring, a better understanding of the effect of S supplementation on discrete microbial populations within the rumen is provided.     

Effects of dietary crude protein and tannic acid on rumen fermentation,rumen microbiota and nutrient digestion in beef cattle

The objectives of the trial were to study the effects of dietary crude protein (CP) and tannic acid (TA) on rumen fermentation, microbiota and nutrient digestion in beef cattle. Eight growing beef cattle (live weight 350 ± 25 kg) were allocated in a 2 × 2 crossover design using two levels of dietary CP [111 g/kg dry matter (DM) and 136 g/kg DM] and two levels of TA (0 and 16.9 g/kg DM) as experimental treatments. Each experimental period lasted 19 d, consisting of 14-d adaptation and 5-d sampling. The impacts of dietary CP and TA on ruminal microbiota were analysed using high-throughput sequencing of 16S rRNA gene. Results indicated that no interactions between dietary CP and TA were found on rumen fermentation and nutrient digestibility. Increasing dietary CP level from 111 to 136 g/kg DM increased the ruminal concentrations of ammonia nitrogen (NH₃-N) (p < 0.01) and improved the CP digestibility (p < 0.001). Adding TA at 16.9 g/kg DM inhibited rumen fermentation and decreased the digestibility of dietary CP (p < 0.001), DM (p < 0.05) and organic matter (p < 0.01). Increasing the dietary CP level or adding TA did not affect the relative abundances of the major bacteria Firmicutes and Proteobacteria at the phylum level and Prevotella_1 and Christensenellaceae_R-7_group at the genus level, even though adding TA increased the Shannon index of the ruminal bacterial community. TA was partly hydrolysed to pyrogallol, gallic acid and resorcinol in rumen fluid and the inhibitory effects of TA on rumen fermentation and nutrient digestibility could have been resulted from the TA metabolites including pyrogallol, gallic acid and resorcinol as well as the protein-binding effect.     

Repeated acidosis challenges and live yeast supplementation shape rumen microbiota and fermentations and modulate inflammatory status in sheep

This study aimed to investigate the impact of repeated acidosis challenges (ACs) and the effect of live yeast supplementation (Saccharomyces cerevisiae I-1077, SC) on rumen fermentation, microbial ecosystem and inflammatory response. The experimental design involved two groups (SC, n=6; Control, n=6) of rumen fistulated wethers that were successively exposed to three ACs of 5 days each, preceded and followed by resting periods (RPs) of 23 days. AC diets consisted of 60% wheat-based concentrate and 40% hay, whereas RPs diets consisted of 20% concentrate and 80% hay. ACs induced changes in rumen fermentative parameters (pH, lactate and volatile fatty-acid concentrations and proportions) as well as in microbiota composition and diversity. The first challenge drove the fermentation pattern towards propionate. During successive challenges, rumen pH measures worsened in the control group and the fermentation profile was characterised by a higher butyrate proportion and changes in the microbiota. The first AC induced a strong release of rumen histamine and lipopolysaccharide that triggered the increase of acute-phase proteins in the plasma. This inflammatory status was maintained during all AC repetitions. Our study suggests that the response of sheep to an acidosis diet is greatly influenced by the feeding history of individuals. In live yeast-supplemented animals, the first AC was as drastic as in control sheep. However, during subsequent challenges, yeast supplementation contributed to stabilise fermentative parameters, promoted protozoal numbers and decreased lactate producing bacteria. At the systemic level, yeast helped normalising the inflammatory status of the animals.     

荷斯坦奶牛瘤胃微生物元基因组BAC文库的构建与分析

采用未培养技术和脉冲场电泳技术直接从瘤胃微生物提取到大小在2Mb左右混合微生物DNA,经HindⅢ不完全酶切获得50～100kbDNA片段,将其连接在pCC1BAC载体上,转化E.coliEPI300,得到瘤胃微生物BAC文库,经对文库的鉴定分析,该文库的平均插入片段54.5kb,空载体率小于2%,库容837Mb,共保存15360个克隆。通过对该文库进行部分酶活性筛选,获得具有淀粉酶活性的克隆16个;纤维素酶活性的克隆26个,而且能降解纤维素的克隆中25个呈现多酶活性。这些结果表明该文库具有重要研究价值。     

Exploring the relationship between bacterial genera and lipid metabolism in bovine rumen

The rumen is characterised by a complex microbial ecosystem, which is particularly active in lipid metabolism. Several studies demonstrated a role of diet and breed on bacterial community profile, with the effect on metabolic pathways. Despite the knowledge achieved on metabolism and the bacterial profile, little is known about the relationship between individual bacteria and metabolic pathways. Therefore, a multivariate approach was used to search for possible relationships between bacteria and products of several pathways. The correlation between rumen bacterial community composition and rumen lipid metabolism was assessed in 40 beef steers (20 Maremmana and 20 Aubrac) reared with the same system and fed the same diet. A canonical discriminant analysis combined with a canonical correlation analysis (CCA) was performed to explore this correlation. The variables showing a Pearson correlation higher than 0.6 as absolute value and significant were retained for CCA considering the relationship of bacterial composition with several metabolic pathways. The results indicated that some bacterial genera could have significant impacts on the presence of several fatty acids. However, the relationship between genera and fatty acid changes according to the breed, demonstrating that the metabolic pathways change according to the host genetic background, related to breed evolution, although there is also an intra-breed genetic background which should not be ignored. In Maremmana, Succiniclasticum and Rikenellaceae_RC9_gut_group showed a high positive correlation with dimethylacetals (DMAs) DMA_C13:0, DMA_C14:0, DMA_C14:0iso, DMA_C15:0, DMA_C15:0iso, and DMA_C18:0. Prevotellaceae_UCG-003 correlates with C18:3c9c12c15 and C18:1t11, while Fibrobacter and Succiniclasticum correlate with C18:2c9t11 and Lachnospiraceae_NK3A20_group correlates with C18:1c12. Prevotellaceae_UCG-003, Ruminococcaceae_UCG-010, and Oribacterium showed a positive correlation with C13:0iso, and C17:0. Conversely, in Aubrac, Treponema_2 and Rikenellaceae_RC9_gut_group correlated with DMA_C14:0iso, DMA_C16:0iso, DMA_C17:0iso, while Ruminococcaceae_UCG-010, Christensenellaceae_R-7_group and Ruminococcaceae_NK4A214_group correlated with DMA_C18:1t11, DMA_C14:0, DMA_C18:1c12. Acetitomaculum correlated with C18:2c9c12, C18:1c12, C18:1c13, C18:1t12 and Lachnospiraceae_NK3A20_group with C18:1t6-8 and C18:1t9. Saccharofermentas, Ruminococcaceae_UCG-010 and Rikenellaceae_RC9_gut_group correlated with C18:2c9t11 while, Prevotellaceae_UCG-001 and Ruminococcus_1 correlated with C14:0iso, C15:0, C15:0iso, C17:0. Saccharofermentans, Rikenellaceae_RC9_gut_group, Ruminococcaceae_NK4A214_group, and Ruminococcaceae_UCG-010 correlated with C13:1c12 and C16:0iso. These results lead to hypothesise a possible association between several metabolic pathways and one or a few bacterial genera. If these associations are confirmed by further investigations that verify the causality of a bacterial genus with a particular metabolic process, it will be possible to deepen the knowledge on the activity of the rumen population in lipid metabolism. This approach appears to be a promising tool for uncovering the correlation between bacterial genera and products of rumen lipid metabolism.     

牛瘤胃分离菌株静息细胞培养体系生物转化黄豆苷原

从牛瘤胃胃液中分离了一株在厌氧条件下能利用其生长细胞将大豆异黄酮黄豆苷原高效还原为二氢黄豆苷原的革兰氏阳性细菌菌株Niu-O16。研究了菌株Niu-O16静息细胞体系转化黄豆苷原的最佳转化条件,通过单因素试验确定菌株Niu-O16静息细胞转化黄豆苷原的最佳条件是:初始pH6.0～8.0,静息细胞浓度32～64mg/mL(湿重),加入底物浓度0.8～1.2mmol/L。通过正交试验确定了静息细胞浓度、加入底物浓度及转化时间的最佳组合为:静息细胞浓度32mg/mL、加入底物浓度0.8mmol/L、转化时间24h;最佳转化条件下底物转化率最高为63.9%。该结果为厌氧菌的静息细胞转化及工业应用提供了参考。     

In vitro studies of the metabolism of [14C]- n-alkanes using ruminal fluid of sheep as substrate

Whether the rumen microbes are able to synthesize and/or degrade long-chain alkanes in anaerobic conditions remains a question to be answered before these hydrocarbons can be confidently used as duodenal flow or rumen transit markers. In this context, an experiment in vitro was carried out to establish whether within a rumen liquor fermentation system, n-alkanes can be derived from de-waxed structures of the plant or from non-alkane wax components (long-chain fatty alcohols, long-chain fatty acids and esters), or may be metabolized by bacteria to other components or to shorter-chain hydrocarbons. Ryegrass was labelled with 14C in growth chambers under controlled conditions in order to use it as a substrate. The labelled material obtained was separated in three fractions: labelled alkanes, labelled de-waxed plant and labelled wax components without the alkanes. These fractions were used for three different incubations in vitro, which objectives were as follows: 1. To check whether rumen bacteria can synthesize alkanes from carbon structures other than waxes (e.g. sugars). 2. To verify whether rumen bacteria can metabolize the n-alkanes to other compounds. 3. To check whether rumen bacteria can synthesize n-alkanes from other carbon compounds from waxes. The results showed that there was neither bacterial synthesis nor metabolism of the n-alkanes in in vitro conditions.     

The effect of rumen ciliates on chitinolytic activity,chitin content and the number of fungal zoospores in the rumen fluid of sheep

The objective of this study was to investigate the effect of selected protozoa on the degradation and concentration of chitin and the numbers of fungal zoospores in the rumen fluid of sheep. Three adult ewes were fed a hay-concentrate diet, defaunated, then monofaunated with Entodinium caudatum or Diploplastron affine alone and refaunated with natural rumen fauna. The average density of the protozoa population varied from 6.1 · 10⁴ (D. affine) to 42.2 · 10⁴ cells/ml rumen fluid (natural rumen fauna). The inoculation of protozoa in the rumen of defaunated sheep increased the total activity of chitinolytic enzymes from 2.9 to 3.6 μmol N-acetylglucosamine/g dry matter (DM) of rumen fluid per min, the chitin concentration from 6.3 to 7.2 mg/g DM of rumen fluid and the number of fungal zoospores from 8.1 to 10.9 · 10⁵ cells/ml rumen fluid. All examined indices showed diurnal variations. Ciliate population density was highest immediately prior to feeding and lowest at 4 h thereafter. The opposite effects were observed for the numbers of fungal zoospores, the chitin concentration and chitinolytic activity. Furthermore, it was found that chitin from zoospores may account for up to 95% of total microbial chitin in the rumen fluid of sheep. In summary, the examined ciliate species showed the ability of chitin degradation as well as a positive influence on the development of the ruminal fungal population.     

Characterization of rumen bacterial diversity and fermentation parameters in concentrate fed cattle with and without forage

Aims: To determine the effects of the removal of forage in high‐concentrate diets on rumen fermentation conditions and rumen bacterial populations using culture‐independent methods. Methods and Results: Detectable bacteria and fermentation parameters were measured in the solid and liquid fractions of digesta from cattle fed two dietary treatments, high concentrate (HC) and high concentrate without forage (HCNF). Comparison of rumen fermentation conditions showed that duration of time spent below pH 5·2 and rumen osmolality were higher in the HCNF treatment. Simpson’s index of 16S PCR‐DGGE images showed a greater diversity of dominant species in the HCNF treatment. Real‐time qPCR showed populations of Fibrobacter succinogenes (P = 0·01) were lower in HCNF than HC diets. Ruminococcus spp., F. succinogenes and Selenomonas ruminantium were at higher (P ≤ 0·05) concentrations in the solid vs the liquid fraction of digesta regardless of diet. Conclusions: The detectable bacterial community structure in the rumen is highly diverse. Reducing diet complexity by removing forage increased bacterial diversity despite the associated reduction in ruminal pH being less conducive for fibrolytic bacterial populations. Quantitative PCR showed that removal of forage from the diet resulted in a decline in the density of some, but not all fibrolytic bacterial species examined. Significance and Impact of the Study: Molecular techniques such as DGGE and qPCR provide an increased understanding of the impacts of dietary changes on the nature of rumen bacterial populations, and conclusions derived using these techniques may not match those previously derived using traditional laboratory culturing techniques.     

Spatial and temporal variations of the bacterial community in the bovine digestive tract

Aims:  Improved knowledge of the bacterial community of the digestive tract is required to enhance the efficiency of digestion in herbivores. This work aimed to study spatial and temporal variations of the bacterial communities in the bovine digestive tract and their correlation with gut environmental parameters.
Methods and Results:  Rumen content and faeces of five cows were sampled for 3 weeks. In addition, reticulum content was sampled during the third week. Bacterial communities were assessed by studying capillary electrophoresis single-stranded conformation polymorphism (CE-SSCP) profiles of 16S rRNA genes. The bacterial community structure differed between the forestomach and faecal contents. The abundance of several operational taxonomic units changed from week to week. Bacterial community structure of the rumen was correlated to propionic acid and NH₃–N concentrations.
Conclusions:  The bacterial community of the bovine digestive tract varied in space and time.
Significance and Impact of the Study:  The study of the bacterial communities of the digestive tract in herbivores should be widened from the rumen to the large intestine. The amplitude and origin of the temporal variation of the ruminal bacterial community need to be better understood to improve the control of the fermentative activity in herbivores.     

Degradation of terpenes and terpenoids from Mediterranean rangelands by mixed rumen bacteria in vitro

This in vitro study aimed at estimating the disappearance rates of 14 terpenes and terpenoids after 24-h incubation with mixed bacteria from caprine rumens. These compounds comprised nine monoterpene hydrocarbons (δ-3-carene, p-cymene, β-myrcene, (E)- and (Z)-β-ocimene, α-phellandrene, α-terpinene, γ-terpinene and α-terpinolene), four oxygenated monoterpenes ((E)- and (Z)-linalool oxide, 4-terpinenol, α + γ terpineol) and one sesquiterpene hydrocarbon (β-cedrene). They were individually exposed to goat rumen microflora for 24 h in 70 ml culture tubes at an input level of 0.5 ml/l. Terpenoids were the least degraded, 100% of (E)-linalool oxide, 95% of (Z)-linalool oxide, 91% of 4-terpinenol and 75% of terpineol remained intact after 24-h incubation. In contrast, α-terpinolene concentration in fermentation broth extracts was below quantification limit, thus indicating an extensive, if not complete, degradation by rumen bacteria. Only 2% of the initial amounts of α-phellandrene were recovered. The other monoterpenes and β-cedrene were partly degraded, with losses ranging from 67% for δ-3-carene to 90% for (E)-β-ocimene. The corresponding rates of disappearance were between 2.67 and 4.08 μmol/ml inoculum per day.     

细菌性阴道病与阴道微生物群相关性研究进展

细菌性阴道病(bacterial vaginosis,BV)是育龄妇女最常见的阴道感染性疾病之一,细菌性阴道病的发生受到年龄、生活习惯等多种因素的影响。然而,其具体发病机制仍未完全阐明,缺乏有效的治疗手段。近年来,多数研究认为细菌性阴道病的发生是由于阴道微生物群失调,乳杆菌减少,其他病原菌增多的结果。正常女性阴道微生物群可被分为5种状态类型,这些状态类型中微生物的紊乱是发生细菌性阴道病最直接的原因。本文通过与正常状态下阴道微生物组成的对比,综述了细菌性阴道病状态下阴道微生物群的不同变化及其影响因素的相关研究,并对以阴道微生物群作为靶标的细菌性阴道病治疗新方法和新进展进行了讨论与对比。     

Influence of methylamine on anaerobic rumen bacterial growth and plant fiber digestion

Anaerobic rumen bacteria were screened for growth inhibition by methylamine. Under nitrogen-limited growth conditions only Ruminobacter amylophilus, Prevotella ruminicola and Megasphaera elsdenii were significantly inhibited. Ruminobacter amylophilus was inhibited more than any other species. Inhibition of R. amylophilus growth occured at all increments in methylamine for all NH₄Cl concentrations tested (0·2–1·8 m ). Dimethylamine was less inhibitory, while trimethyl-, ethyl- and diethylamine were not inhibitory. When methylamine was added to in vitro mixed culture, ruminal fermentations containing alfalfa, neutral detergent fiber disappearance and ammonia production were not affected. This suggests that although methylamine may inhibit specific rumen bacteria, it does not alter overall mixed ruminal microorganism activities with alfalfa as a substrate.