饲粮中添加海南霉素对奶牛瘤胃发酵及甲烷产量的影响

本试验旨在研究海南霉素对荷斯坦奶牛瘤胃发酵模式及甲烷产量的影响。试验选用3头装有永久性瘤胃瘘管、体况相近的中国荷斯坦奶牛,采用3×3拉丁方试验设计,试验分为3期,每期15 d,试验设负对照组(不添加任何添加剂)、正对照组(添加10 mg/kg莫能菌素)和海南霉素组(添加7.2 mg/kg海南霉素)。结果表明:饲粮中添加海南霉素后,除在采食后2 h显著提高奶牛瘤胃内pH(P<0.05)外,其他时间均无显著影响(P>0.05);采食后0、2、8和10 h,海南霉素组氨态氮(NH3-N)浓度均显著低于负对照组(P<0.05),而采食后6 h,海南霉素有抑制NH3-N释放的趋势(P=0.06);采食后0、2、4和6 h,海南霉素组乙酸浓度及乙酸与丙酸的比值与负对照组相比均显著降低(P<0.05),丙酸浓度显著升高(P<0.05),总挥发性脂肪酸和丁酸浓度没有显著变化(P>0.05)。海南霉素显著抑制了瘤胃甲烷的产生(P=0.02),海南霉素组的奶牛甲烷呼出量为216.50 L/d,比负对照组降低了14.03%。由此得出结论:饲粮中添加海南霉素可以改变奶牛瘤胃的发酵类型,使其更趋向于丙酸型发酵,并显著降低动物的甲烷呼出量。     

Effect of α-cyclodextrin-allyl isothiocyanate on ruminal microbial methane production in vitro

The objective of the present study was to investigate the effects of α‐cyclodextrin‐allyl isothiocyanate (CD‐AI) on ruminal microbial methane production and rumen fermentation of corn starch, soluble potato starch or hay plus concentrate (1.5:1) by mixed rumen microorganisms. Diluted rumen fluid (30 mL) was incubated anaerobically at 38°C for 6 and 24 h with or without CD‐AI (0, 0.4, 0.8, 1.6 and 3.2 g/L). The pH of the medium was unchanged by CD‐AI in all substrates. The molar proportion of acetate was decreased and propionate was increased with a corresponding decrease in acetate : propionate ratio (P < 0.05). Total volatile fatty acids and butyrate were increased (P < 0.05). Ammonia‐N was decreased (P < 0.05). Except with soluble potato starch, numbers of protozoa were unchanged after 6 h. As concentration of CD‐AI increased from 0 to 3.2 g/L, fermentation of corn starch, soluble potato starch and hay plus concentrate resulted in decreased (P < 0.05) methane production of 49–100% (6 h) and 14–100% (24 h); 39–100% (6 h) and 16–100% (24 h); and 45–100% (6 h) and 17–100% (24 h), respectively. When hay plus concentrate was used as substrate, methanogenic bacteria were decreased (P < 0.05) with 0.8 g/L of CD‐AI after 6 h. Excluding the lower dose level (0.4 g/L) of CD‐AI, digestibility of neutral detergent fiber of hay plus concentrate was decreased (P < 0.05) after 24 h. A suitable level of CD‐AI could therefore be used as a supplement to inhibit methane production and improve rumen fermentation without detrimental effects on fiber digestion.     

Induction of a transient acidosis in the rumen simulation technique

Feeding high concentrate diets to cattle results in an enhanced production of short‐chain fatty acids by the micro‐organisms in the rumen. Excessive fermentation might result in subclinical or clinical rumen acidosis, characterized by low pH, alterations in the microbial community and lactate production. Here, we provide an in vitro model of a severe rumen acidosis. A transient acidosis was induced in the rumen simulation technique by lowering bicarbonate, dihydrogen phosphate and hydrogen phosphate concentrations in the artificial saliva while providing a concentrate‐to‐forage ratio of 70:30. The experiment consisted of an equilibration period of 7 days, a first control period of 5 days, the acidosis period of 5 days and a second control period of 5 days. During acidosis induction, pH decreased stepwise until it ranged below 5.0 at the last day of acidosis (day 17). This was accompanied by an increase in lactate production reaching 11.3 mm at day 17. The daily production of acetate, propionate and butyrate was reduced at the end of the acidosis period. Gas production (methane and carbon dioxide) and NH₃‐N concentration reached a minimum 2 days after terminating the acidosis challenge. While the initial pH was already restored 1 day after acidosis, alterations in the mentioned fermentation parameters lasted longer. However, by the end of the experiment, all parameters had recovered. An acidosis‐induced alteration in the microbial community of bacteria and archaea was revealed by single‐strand conformation polymorphism. For bacteria, the pre‐acidotic community could be re‐established within 5 days, however, not for archaea. This study provides an in vitro model for a transient rumen acidosis including biochemical and microbial changes, which might be used for testing feeding strategies or feed additives influencing rumen acidosis.     

Effects of supplemental lauric acid-rich oils in high-grain diet on in vitro rumen fermentation

A series of in vitro studies were performed to evaluate the effects of lauric acid (LA)‐rich oils on rumen fermentation with a high‐grain diet. Soy oil (SO) and palm oil (PO) as long‐chain fatty acid triglycerides, palm kernel oil (PKO), coconut oil (CO), powdered coconut oil (pCO) and coconut oil calcium salt (COCa) as medium‐chain LA‐rich oils were used as tested additives. Rumen fluid from steers fed high‐grain diet was incubated with ground corn with or without oil supplementation (2.0 g/L) for 6 h at 39°C to monitor rumen products. Methane production decreased, while hydrogen production increased on LA‐rich oils except COCa. All the LA‐rich oils increased total volatile fatty acids (VFA) production and molar proportion of propionate. Also, amylase activity in culture was higher when these oils were added. The most potent additives, pCO and free LA, were further tested to determine dose–response of rumen fermentation. Powdered coconut oil and LA altered rumen fermentation toward more propionate production by supplementation at 1.2 and 0.3 g/L, respectively. These results suggest that some LA‐rich oils and free LA could be used for improving rumen fermentation under high‐grain diet feeding conditions.     

Dynamics of methanogenesis,ruminal fermentation and fiber digestibility in ruminants following elimination of protozoa: a meta-analysis

Background: Ruminal microbes are vital to the conversion of lignocellulose-rich plant materials into nutrients for ruminants.Although protozoa play a key role in linking ruminal microbial networks,the contribution of protozoa to rumen fermentation remains controversial; therefore,this meta-analysis was conducted to quantitatively summarize the temporal dynamics of methanogenesis,ruminal volatile fatty acid(VFA) profiles and dietary fiber digestibility in ruminants following the elimination of protozoa(also termed defaunation).A total of 49 studies from 22 publications were evaluated.Results: The results revealed that defaunation reduced methane production and shifted ruminal VFA profiles to consist of more propionate and less acetate and butyrate,but with a reduced total VFA concentration and decreased dietary fiber digestibility.However,these effects were diminished linearly,at different rates,with time during the first few weeks after defaunation,and eventually reached relative stability.The acetate to propionate ratio and methane production were increased at 7 and 11 wk after defaunation,respectively.Conclusions: Elimination of protozoa initially shifted the rumen fermentation toward the production of more propionate and less methane,but eventually toward the production of less propionate and more methane over time.     

Reducing methane production by supplementation of Terminalia chebula RETZ. containing tannins and saponins

This study investigates the effects of Terminalia chebula Retz. meal supplementation on rumen fermentation and methane (CH₄) production by using an in vitro gas technique. The experimental design was a completely randomized design (CRD) and the dietary treatments were T. chebula supplementation at 0, 4, 8, 12, 16 and 20 mg with 0.5 g of roughage and concentrate ratio at 60:40. The results revealed that cumulative gas production (96 h of incubation) were higher (P < 0.01) with T. chebula supplementation at 12, 16 and 20 mg than other treatments. However, in vitro dry matter degradability (IVDMD) and in vitro organic matter digestibility (IVOMD) were not significantly different among treatments (P > 0.05). The NH₃‐N concentrations tended to quadratically increase with increasing levels of T. chebula in the diet. In addition, total volatile fatty acids (VFA) and propionate concentrations were increased (P < 0.01), while acetate concentration, acetate‐to‐propionate ratio, CH₄ production and protozoal populations were decreased (P < 0.01) when supplemented with T. chebula at 8, 12 and 16 mg, respectively. Based on this study, it could be concluded that supplementation of T. chebula at 12 mg could improve rumen fermentation by reducing CH₄ production and protozoa populations, thus improving in vitro gas production and VFA profiles.     

Tropical legume supplementation influences microbial protein synthesis and rumen ecology

Four rumen‐fistulated male swamp buffaloes, 5‐year‐old with initiated live weight at 360 ± 12 kg, were randomly assigned according to a 4 × 4 Latin square design to investigate the effect of feeding high level of dried Leucaena leaf (DLL) on feed intake, fermentation efficiency and microbial protein synthesis. The dietary treatments were the feeding levels of DLL at 0, 2, 4 and 6 kg/head/day. All buffaloes were supplemented with concentrate mixtures at 0.1% of body weight, and rice straw was fed ad libitum with the availability of water and mineral block at all time. The results revealed that the total feed intake and nutrient digestibility were significantly improved with the increasing levels of DLL feeding, and the highest was in the buffaloes consuming DLL at 6 kg/head/day. Feeding high levels of DLL did not affect on ruminal pH and temperature, while ammonia nitrogen, blood urea nitrogen and volatile fatty acid concentration were significantly enhanced. Moreover, methane production was dramatically reduced by increasing levels of DLL feeding. Total direct counts of the micro‐organism population were increased with the increasing levels of DLL feeding. According to the application of quantitative PCR to quantity cellulolytic bacteria (16S rRNA) targets, it was found that the population of total bacteria and Fibrobactor succinogenes was affected by treatments, while Ruminococcus flavefaciens and methanogen population were significantly decreased as buffaloes were fed with DLL. The nitrogen balance and microbial nitrogen supply were remarkably improved with the increasing levels of DLL feeding. Based on this study, it could be concluded that high levels of DLL feeding at 6 kg/head/day could enhance feed intake, nutrient digestibility, rumen fermentation efficiency and microbial protein synthesis in swamp buffaloes fed on rice straw without any adverse effect.     

Effects of nitrate addition to a diet on fermentation and microbial populations in the rumen of goats,with special reference to Selenomonas ruminantium having the ability to reduce nitrate and nitrite

This study investigated the effects of dietary nitrate addition on ruminal fermentation characteristics and microbial populations in goats. The involvement of Selenomonas ruminantium in nitrate and nitrite reduction in the rumen was also examined. As the result of nitrate feeding, the total concentration of ruminal volatile fatty acids decreased, whereas the acetate : propionate ratio and the concentrations of ammonia and lactate increased. Populations of methanogens, protozoa and fungi, as estimated by real‐time PCR, were greatly decreased as a result of nitrate inclusion in the diet. There was modest or little impact of nitrate on the populations of prevailing species or genus of bacteria in the rumen, whereas Streptococcus bovis and S. ruminantium significantly increased. Both the activities of nitrate reductase (NaR) and nitrite reductase (NiR) per total mass of ruminal bacteria were increased by nitrate feeding. Quantification of the genes encoding NaR and NiR by real‐time PCR with primers specific for S. ruminantium showed that these genes were increased by feeding nitrate, suggesting that the growth of nitrate‐ and nitrite‐reducing S. ruminantium is stimulated by nitrate addition. Thus, S. ruminantium is likely to play a major role in nitrate and nitrite reduction in the rumen.     

Effect of donor animals and their diet on in vitro nutrient degradation and microbial protein synthesis using grass and corn silages

Two nonlactating cows and two wether sheep, all fitted with a permanent cannula into the rumen, were fed either hay plus concentrate, grass silage or corn silage to study the effect of the donor animal and its diet on in vitro fermentation and microbial protein synthesis. Rumen inoculum was obtained before the morning feeding. Grass silage or corn silage was incubated in a semi‐continuous rumen simulation system for 14 days. Four replicated vessels were used per treatment. Degradation of crude nutrients and detergent fibre fractions as well as microbial protein synthesis and the production of volatile fatty acids were studied. Additionally, total gas and methane production was measured with a standard in vitro gas test. Gas production and methane concentration was higher when the inoculum used was from sheep than that from cows. The donor animal also affected the degradation of organic matter and ether extract as well as the amount of propionate and butyrate, and the acetate‐to‐propionate ratio. The effect of the diet fed to the donor animal on fermentation was much greater than the effect of the donor animal itself. Feeding hay plus concentrate resulted in higher gas production and degradation of acid detergent fibre, but in lower degradation of ether extract and reduced microbial protein synthesis. Additionally, the pattern of volatile fatty acids changed significantly when the diet of the donor animals was hay plus concentrate or one of the silages. These results show that in vitro fermentation and microbial protein synthesis is different when based on inoculum from either cattle or sheep. The diet fed to the donor animal is more important than the animal species and is probably mediated by an adjusted microbial activity. With regard to standardized feed evaluations, these results further support the need to harmonize in vitro approaches used in different laboratories.     

Effect of cashew nut shell liquid on metabolic hydrogen flow on bovine rumen fermentation

Effect of cashew nut shell liquid (CNSL), a methane inhibitor, on bovine rumen fermentation was investigated through analysis of the metabolic hydrogen flow estimated from concentrations of short‐chain fatty acids (SCFA) and methane. Three cows were fed a concentrate and hay diet without or with a CNSL‐containing pellet. Two trials were conducted using CNSL pellets blended with only silica (trial 1) or with several other ingredients (trial 2). Methane production was measured in a respiration chamber system, and energy balance and nutrient digestibility were monitored. The estimated flow of metabolic hydrogen demonstrated that a part of metabolic hydrogen was used for hydrogen gas production, and a large amount of it flowed into production of methane and SCFA in both trial 1 and 2, when CNSL was administered to the bovine rumen. The results obtained by regression analyses showed that the effect of CNSL supply on methane reduction was coupled with a significant (P < 0.01) decrease of acetate and a significant (P < 0.01) increase of propionate and hydrogen gas. These findings reveal that CNSL is able to reduce methane and acetate production, and to increase hydrogen gas and propionate production in vivo.     

Dietary dragon fruit (Hylocereus undatus) peel powder improved in vitro rumen fermentation and gas production kinetics

Plant phytophenols especially condensed tannins (CT) and saponins (SP) have been demonstrated to impact on rumen fermentation. Dragon fruit (Hylocereus undatus) peel powder (DFPP) contains both CT and SP. The current study aimed to investigate the influence of DFPP and varying levels of concentrate and roughage ratios on gas production kinetics, nutrient degradability, and methane production “using in vitro gas production technique.” The dietary treatments were arranged according to a 3?×?5 Factorial arrangement in a completely randomized design. The two experimental factors consisted of the roughage to concentrate (R:C) ratio (100:0, 70:30, and 30:70) and the levels of DFPP supplementation (0, 1, 2, 3, and 4% of the substrate) on DM basis. The results revealed that the R:C ratio at 30:70 had the highest cumulative gas production when compared to other ratios (P?<?0.01). The in vitro true dry matter degradability at 12 and 24 h was affected by R:C ratio (P?<?0.01). Furthermore, volatile fatty acids (VFA) and propionate (C3) were significantly increased by the levels of DFPP, while acetate (C2) and C2:C3 ratios were decreased (P?<?0.05). The rumen protozoal population was significantly decreased by DFPP supplementation (P?<?0.05). Rumen methane production was significantly impacted by R:C ratios and decreased when the level of DFPP increased (P?<?0.01), while NH₃-N and ruminal pH were not influenced by the DFPP supplement. It could be summarized that supplementation of DFPP resulted in improved rumen fermentation kinetics and could be used as a dietary source to mitigate rumen methane production, hence reducing greenhouse gas production.

     

Feeding cashew nut shell liquid decreases methane production from feces by altering fecal bacterial and archaeal communities in Thai local ruminants

The effect of feeding cashew nut shell liquid (CNSL) on fecal fermentation products and microbiota was investigated in Thai native cattle and swamp buffaloes. Four of each animal were fed rice straw and concentrate diet with control pellets without CNSL for 4 weeks, followed by the same diet with pellets containing CNSL for another 4 weeks, so that CNSL was administered at a level of 4 g/100 kg body weight. Feces were collected the last 2 days in each feeding period. CNSL alkyl phenols were recovered from feces (16%–28%) in a similar proportion to those in the diet, indicating that most functional anacardic acid was not selectively removed throughout the digestive tract. In vitro production of gas from feces, particularly methane, decreased with CNSL feeding. The proportion of acetate in feces decreased with CNSL feeding, whereas that of propionate increased, without affecting total short-chain fatty acid concentration. CNSL feeding changed fecal microbial community, particularly in swamp buffaloes, which exhibited decreases in the frequencies of Treponema, unclassified Ruminococcaceae, and Methanomassiliicoccaceae. These results suggest that CNSL feeding alters not only rumen fermentation but also hindgut fermentation via modulation of the microbial community, thereby potentially attenuating methane emission from the feces of ruminant animals.     

Effect of Bacillus subtilis C-3102 supplementation in milk replacer on growth and rumen microbiota in preweaned calves

We aimed to assess the effect of feeding Bacillus subtilis C-3102 on the growth and rumen microbiota in the preweaned calves. Twelve newborn Japanese Black calves were randomly allocated to either the control (n = 6) or the treatment (n = 6) groups in the present study. Calves in the treatment group were offered B. subtilis C-3102 supplemented milk replacer throughout the preweaning period. Rumen fermentation during the first 21 days of life seemed to be slightly suppressed by feeding B. subtilis C-3102. This fermentation shift was probably attributed to the lower abundance of the core members of rumen microbiota until 21 days of age in the calves fed B. subtilis C-3102. However, feeding B. subtilis C-3102 did not influence the abundance of the core members of rumen microbiota at 90 days of age. Distribution of Sharpea spp. and Megasphaera spp., which potentially contribute to low methane production and are regarded as beneficial rumen bacteria, was higher in the rumen of calves fed B. subtilis C-3102 at 90 days of age. These results suggest that B. subtilis C-3102 supplementation in milk replacer could potentially contribute to the improvement of feed efficiency after weaning via the establishment of beneficial rumen bacteria.     

Preliminary study of the effects of condensed barley distillers soluble on rumen fermentation and plasma metabolites in Japanese Black cows

In Japan, condensed barley distillers soluble (CBDS) is a widely known liquor byproduct that contains a high level of protein and is used as a supplementary protein feed for cattle. The present study evaluated the effects of CBDS feed on rumen fermentation and plasma metabolites in Japanese Black cows. Applying a replicated 3 × 3 Latin square design, nine cows were offered CBDS and hay (CBDS‐t), soy bean meal and hay (Soybean‐t) and only hay (Hay‐t) over 35 days. We collected ruminal fluid and plasma just before feeding and at 3 h after feeding. The concentrations of propionate and butyrate in the rumen before feeding were lower in the CBDS‐t than in the Soybean‐t group (P < 0.05). However, after 3 h, the concentrations were higher in the CBDS‐t than in the Soybean‐t and Hay‐t groups (P < 0.05). Although, there were no differences in the compositions (% mol) of propionate and butyrate in the rumen and the concentration of plasma β‐hydroxybutyric acid before feeding between treatments, after 3 h they were significantly higher in the CBDS‐t than in the Soybean‐t and Hay‐t groups (P < 0.05). These results indicate that feeding CBDS promotes rumen fermentation and butyrate metabolism.     

Effect of ethanol on nitrate and nitrite reduction and methanogenesis in the ruminal microbiota

The effect of ethanol on nitrate and nitrite reduction was examined by conducting in vitro experiments with mixed ruminal microbes. The addition of ethanol to cultures of mixed ruminal microbes stimulated nitrate reduction, and, to a greater extent, nitrite reduction, which resulted in a decrease in nitrite accumulation. However, known nitrate‐reducing ruminal bacteria, such as Selenomonas ruminantium, Veillonella parvula and Wolinella succinogenes, were unable to utilize ethanol directly as an electron donor for nitrate reduction. No nitrate‐reducing bacterium capable of utilizing ethanol was found in the rumen of goats. However, when mixed ethanol‐utilizing, hydrogen gas (H₂)‐producing bacteria (Ruminococcus albus and Ruminococcus flavefaciens) were added to the culture of the mixed nitrate‐reducing bacteria described above, nitrate and nitrite reduction was observed. These results suggest that the nitrate‐reducing bacteria utilized the H₂ that was produced from ethanol oxidation by the ethanol‐utilizing bacteria as an electron donor. It is conceivable that the stimulation of nitrate and nitrite reduction by ethanol, observed in the culture of mixed ruminal microbes, was a result of electron transfer from ethanol to nitrate, and nitrite through H₂, that is, ‘interspecies hydrogen transfer’ from ethanol‐metabolizing bacteria to nitrate‐reducing bacteria. Thus, the addition of ethanol to high‐nitrate diets may be effective for preventing nitrate poisoning. Furthermore, methane production was reduced to less than one‐third by the addition of mixed nitrate‐reducing bacteria to the co‐culture of mixed methanogens with mixed ethanol‐utilizing bacteria incubated in a medium containing ethanol and nitrate. Therefore, the addition of ethanol and nitrate may decrease methanogenesis without suppressing overall fermentation in the rumen.     

Effect of cyclodextrin diallyl maleate on methane production, ruminal fermentation and microbes in vitro and in vivo

Effects of β‐cyclodextrin diallyl maleate (CD‐M) on methane production, ruminal fermentation and digestibility were studied both in vitro and in vivo. In in vitro study, diluted ruminal fluid (30 mL) was incubated anaerobically at 38°C for 6 and 24 h with or without CD‐M using hay plus concentrate (1.5:1) as a substrate. The CD‐M was added at different concentrations (0, 1.25, 2.5, 5.0 and 7.5 g/L). The pH of the medium and numbers of protozoa were not affected by the addition of CD‐M. Total volatile fatty acids were increased and ammonia‐N was decreased, molar proportion of acetate was decreased and propionate was increased (P < 0.05) by CD‐M. Methane was inhibited (P < 0.05) by 14–76%. The effect of CD‐M on methane production and ruminal fermentation was further investigated in vivo using four Holstein steers in a cross‐over design. The steers were fed Sudangrass hay and concentrate mixture (1.5:1) with or without CD‐M (2% of feed dry matter) as a supplement. Ruminal proportion of acetate tended to decrease and that of propionate was increased (P < 0.05) 2 h after CD‐M dosing. Total viable counts, cellulolytic, sulfate reducing, acetogenic bacteria and protozoa were unaffected while methanogenic bacteria were decreased (P < 0.05) by CD‐M. The plasma concentration of glucose was increased, whereas that of urea‐N was decreased (P < 0.05). Methane was inhibited (P < 0.05) from 36.4 to 30.1 L/kg dry matter intake by the addition of CD‐M. Apparent digestibilities of dry matter and neutral detergent fiber were not affected while that of crude protein was increased (P < 0.05) in the medicated steers. These data suggested that dietary supplementation of CD‐M decreased methane production and improved nutrient use.     

In vitro rumen fermentation and digestibility of buffaloes as influenced by grape pomace powder and urea treated rice straw supplementation

This study aimed to investigate the effect of grape pomace powder levels and roughage sources on gas kinetics, digestibility and fermentation of swamp buffaloes by using in vitro techniques. The experimental design was a 2 × 4 factorial arrangement in a completely randomized design. Factor A was two sources of roughage (untreated rice straw, RS, and 3% urea treated rice straw, UTRS) and factor B was four levels of grape pomace powder (GPP) supplementation (0, 2, 4, 6% of substrate) on a dry matter basis. Results revealed that GPP supplementation at 2, 4 and 6% of substrate influenced gas kinetics. Cumulative gas production tended to be lower in the supplemented group. In vitro true digestibility was higher in the GPP supplementation at 2% with UTRS while microbial mass was higher in the supplemented groups. Supplementation of GPP significantly increased the total volatile fatty acids, especially propionate. Calculated methane production was subsequently decreased in the supplemented groups. Bacterial population was higher while protozoal population was lower by GPP supplementation. It could be concluded that supplementation of GPP at 2% of the substrate with UTRS improved in vitro true digestibility, rumen fermentation end‐products as well as reducing methane production.     

Conjugated fatty acids and methane production by rumen microbes when incubated with linseed oil alone or mixed with fish oil and/or malate

We hypothesized that manipulating metabolism with fish oil and malate as a hydrogen acceptor would affect the biohydrogenation process of α‐linolenic acid by rumen microbes. This study was to examine the effect of fish oil and/or malate on the production of conjugated fatty acids and methane (CH₄) by rumen microbes when incubated with linseed oil. Linseed oil (LO), LO with fish oil (LO‐FO), LO with malate (LO‐MA), or LO with fish oil and malate (LO‐FO‐MA) was added to diluted rumen fluid, respectively. The LO‐MA and LO‐FO‐MA increased pH and propionate concentration compared to the other treatments. LO‐MA and LO‐FO‐MA reduced CH₄ production compared to LO. LO‐MA and LO‐FO‐MA increased the contents of c9,t11‐conjugated linoleic acid (CLA) and c9,t11,c15‐conjugated linolenic acid (CLnA) compared to LO. The content of malate was rapidly reduced while that of lactate was reduced in LO‐MA and LO‐FO‐MA from 3 h incubation time. The fold change of the quantity of methanogen related to total bacteria was decreased at both 3 h and 6 h incubation times in all treatments compared to the control. Overall data indicate that supplementation of combined malate and/or fish oil when incubated with linseed oil, could depress methane generation and increase production of propionate, CLA and CLnA under the conditions of the current in vitro study.     

Effect of bromochloromethane and fumarate on phylogenetic diversity of the formyltetrahydrofolate synthetase gene in bovine rumen

Effect of the methane inhibitor, bromochloromethane (BCM) and dietary substrate, fumarate, on microbial community structure of acetogen bacteria in the bovine rumen was investigated through analysis of the formyltetrahydrofolate synthetase gene (fhs). The fhs sequences obtained from BCM‐untreated, BCM‐treated, fumarate‐untreated and fumarate‐treated bovine rumen were categorized into homoacetogens and nonhomoacetogenic bacteria by homoacetogen similarity scores. Phylogenetic tree analysis indicated that most of the fhs sequences categorized into homoacetogens were divided into nine clusters, which were in close agreement with a result shown in a self‐organizing map. The diversity of the fhs sequences from the BCM‐treated rumen was significantly different from those from BCM‐non‐treated rumen. Principal component analysis also showed that addition of BCM to the rumen altered the population structure of acetogenic bacteria significantly but the effect of fumarate was comparatively minor. These results indicate that BCM affects diversity of actogens in the bovine rumen, and changes in acetogenic community structure in response to methane inhibitors may be caused by different mechanisms.     

Effects of defaunation and dietary coconut oil distillate on fermentation,digesta kinetics and methane production of Brahman heifers

A 2 × 2 factorial experiment was conducted to assess the effects of presence or absence of rumen protozoa and of dietary coconut oil distillate (COD) supplementation on rumen fermentation characteristics, digesta kinetics and methane production in Brahman heifers. Twelve Brahman heifers were selected to defaunate, with 6 being subsequently refaunated. After defaunation and refaunation, heifers were randomly allocated to COD supplement or no supplement treatments while fed an oaten chaff‐based diet. Methane production (MP; 94.17 v 104.72 g CH₄/d) and methane yield [MY; 19.45 v 21.64 g CH₄/kg dry matter intake (DMI)] were reduced in defaunated heifers compared with refaunated heifers when measured at 5 weeks after refaunation treatment (p < 0.01). Supplement of COD similarly reduced MP and MY (89.36 v 109.53 g/d and 18.46 v 22.63 g/kg DMI, respectively; p < 0.01), and there were no significant interactions of defaunation and COD effects on rumen fermentation or methane emissions. Concentration of total volatile fatty acid (VFA) and molar proportions of acetate, propionate and butyrate was not affected by defaunation or by COD. Microbial crude protein (MCP; g/d) outflow was increased by defaunation (p < 0.01) in the absence of COD but was unaffected by defaunation in COD‐supplemented heifers. There was a tendency towards a greater average daily gain (ADG) in defaunated heifers (p = 0.09), but COD did not increase ADG (p > 0.05). The results confirmed that defaunation and COD independently reduced enteric MP even though the reduced emissions were achieved without altering rumen fermentation VFA levels or gut digesta kinetics.