Artificial Rumen System Research Articles

PSX-B-6 Effect of slow-release urea on gas production, fermentation characteristics, nutrient digestibility and microbial protein synthesis in an artificial rumen system

Abstract The objective of this study was to evaluate the effects of slow-release urea (SRU) on gas production, fermentation parameters, nutrient digestibility, and microbial protein synthesis using artificial rumen system. The experiment was a completely randomized design with four treatments and four replications of each treatment. The treatments were control diet (no SRU), control diet supplemented with 0.28% (U28), 0.56% SRU (U56) or control diet that was added by 1.5% more corn grain and substituted with 0.35% SRU for 1.85% soybean meal (U35-SBM). The diets were formulated to be isoenergetic (1.71 NEL Mcal/kg), but protein concentration was lower (15.48 vs. 16.24%) and starch concentration was higher (28.2 vs. 27.1%) with U35-SBM than other three treatments. Experimental period consisted of 8 d of adaptation and 7 d of sampling. Rumen inoculum was obtained from three ruminally fistulated Angus cows fed the same diet to the substrate incubated. Gas production (L/d) was lower (P = 0.02) with U35-SBM (1.51) than control (1.79) or U28 (1.92); however, methane production was not affected by treatments (average, 47 mg/d). Dry matter digestibility was greater (P < 0.01) with U35-SBM (78.5%) than other treatments (74.6%), which had no differences in DM digestibility. Total volatile fatty acid (VFA) production did not differ among treatments (average, 53.1 mmol/d), but increasing SRU supplementation linearly (P < 0.01) decreased molar proportion of propionate from 27.0 to 25.7% and linearly (P < 0.01) increased acetate to propionate ratio from 1.69 to 1.78. The ammonia nitrogen (N) linearly (P < 0.01) increased from 7.70 to 10.25 mmol/L with increasing SRU addition. Microbial protein synthesis was greater (P = 0.03) with SRU treatments (average, 83.9 mg N/d) than control (78.9 mg N/d). The present results demonstrated the benefits to add the SRU in dairy cow diet for improving ruminal digestibility and microbial protein synthesis.

PSVI-13 Changes in the taxonomic composition of the rumen of ruminants when introducing fat components into the diet

Abstract Fats are concentrated energy sources for cattle growth, but their inclusion in the diet has a huge impact on the taxonomic composition of the rumen. The aim of this study was to evaluate the effect of supplemental linseed oil administration (3% of dry matter (DM) diet) on microbiota and DM digestibility in the rumen. The studies carried out on Kazakh white-headed bull calves, aged 15 months, with chronic rumen fistula (diet - 70% grassland hay, 30% barley grain). Dietary dry matter digestibility (in-vitro in an artificial rumen system, for 24 hours) analyzed daily for 10 days, and microflora (fluid-bound) analyzed using high-throughput 16SrRNA gene sequencing (Illumina). Inclusion of LO showed a slight 3.5% increase in DM digestibility compared to C (52.0% versus 53.9%). The taxonomic composition of the rumen microbiocenosis in group C was mainly represented by the phylum Firmicutes (54.7%) and Bacteroidetes (39.3%), while other phylum numbers were less than 2%. When LO was injected, the dominance of phylum Bacteroidetes (64.2%), phylum Firmicutes (19.3%), and Verrucomicrobia (5.3%) was noted. The calculation of the Shannon index showed an increase in species diversity in the group that received LO. It was H’= 0.76, while in CH’= 0.42. The Simpson dominance index in group C was 0.44, in the group receiving LOD = 0.54. The obtained data show a positive effect. The linseed oil allow to increase the biodiversity of the rumen microbiome and the digestibility of DM feed, which can be used in fattening young cattle. This research performed with financial support from the project 0761-2019-0005.

Effect of Dried Distillers Grains With Solubles and Red Osier Dogwood Extract on Fermentation Pattern and Microbial Profiles of a High-Grain Diet in an Artificial Rumen System.

The objective of this study was to evaluate the effect of dried distillers grains with solubles (DDGS) and red-osier dogwood (ROD) extract on in vitro fermentation characteristics, nutrient disappearance, and microbial profiles using the rumen simulation technique. The experiment was a completely randomized design with a 2 × 2 factorial arrangement of treatments and four replicates per treatment. A basal diet [10% barley silage, 87% dry-rolled barley grain, and 3% vitamin and mineral supplement, dry matter (DM) basis] and a DDGS diet (as per basal diet with 25% of wheat DDGS replacing an equal portion of barley grain) were supplemented with ROD extract at 0 and 1% (DM basis), respectively. The experimental period was 17 d, consisting 10 days of adaptation and 7 days of data and sample collection. The substitution of wheat DDGS for barley grain did not affect gas production; disappearances of DM, organic matter, and crude protein; total volatile fatty acid (VFA) production; and microbial protein production. However, replacing barley grain with wheat DDGS increased (P = 0.01) fermenter pH and molar proportion of branched-chain VFA, switched (P = 0.06) the fermentation pattern to higher acetate production due to increased (P = 0.01) disappearance of neutral detergent fiber (NDF), and decreased (P = 0.08) methane (CH4) production. In the basal barley diet, the ROD extract increased the acetate to propionate (A:P) ratio (P = 0.08) and reduced the disappearance of starch (P = 0.06) with no effect on any other variables. No effects of ROD in the DDGS diet were observed. The number of operational taxonomic unit (OTUs) and the Shannon diversity index of the microbial community had little variation among treatments. Taxonomic analysis revealed no effect of adding the ROD extract on the relative abundance of bacteria at the phylum level with either the basal diet or DDGS diet, while at the genus level, the microbial community was affected by the addition of both DDGS and the ROD extract. Prevotella and Fibrobacter were the most abundant genera in the basal diet; however, Treponema became the most abundant genus with the addition of the ROD extract. These results indicated that the substitution of wheat DDGS for barley grain may mitigate enteric CH4 emissions. The trend of reduced starch fermentability and increased NDF disappearance with the addition of ROD extract suggests a reduced risk of rumen acidosis and an improvement in the utilization of fiber for cattle-fed high-grain diet.

Chitosan as a feed additive: Its modulatory effect on methane emission and biohydrogenation under artificial rumen system

This study aimed to determine the effects of chitosan addition on methane emission, fatty acid biohydrogenation and fermentation profile of rumen simulation technique (rusitec). Four studies reported chitosan use as a feed additive in the rusitec system were integrated into a database. Treatments were categorized into control (no chitosan addition) and chitosan addition at different levels. Various studies were treated as random effects whereas treatments were considered as fixed effects. Data were analyzed by using mixed model methodology. Significance was declared when P<0.05 and tendency was stated when P<0.1. Results showed that chitosan addition reduced methane emission in comparison to control by as much as 28% (P<0.05). Total volatile fatty acid concentration was not altered due to chitosan, but acetate proportion was decreased (P<0.05) while propionate proportion tended to elevate in the addition of chitosan (P<0.1). Chitosan did not influence ruminal pH, ammonia concentration and nutrient digestibility (organic matter, crude protein and neutral detergent fiber) of substrate. Proportions of vaccenic acid (P<0.01) and conjugated linoleic acid (P<0.001) were increased by the addition of chitosan. In conclusion, chitosan may provide beneficial effects in the rumen by mitigating methane emission and elevating fatty acids contributing to human health.

Effects of brewers\u2019 spent grain protein hydrolysates on gas production, ruminal fermentation characteristics, microbial protein synthesis and microbial community in an artificial rumen fed a high grain diet

BackgroundBrewers’ spent grain (BSG) typically contains 20% – 29% crude protein (CP) with high concentrations of glutamine, proline and hydrophobic and non-polar amino acid, making it an ideal material for producing value-added products like bioactive peptides which have antioxidant properties. For this study, protein was extracted from BSG, hydrolyzed with 1% alcalase and flavourzyme, with the generated protein hydrolysates (AlcH and FlaH) showing antioxidant activities. This study evaluated the effects of AlcH and FlaH on gas production, ruminal fermentation characteristics, nutrient disappearance, microbial protein synthesis and microbial community using an artificial rumen system (RUSITEC) fed a high-grain diet.ResultsAs compared to the control of grain only, supplementation of FlaH decreased (P < 0.01) disappearances of dry matter (DM), organic matter (OM), CP and starch, without affecting fibre disappearances; while AlcH had no effect on nutrient disappearance. Neither AlcH nor FlaH affected gas production or VFA profiles, however they increased (P < 0.01) NH3-N and decreased (P < 0.01) H2 production. Supplementation of FlaH decreased (P < 0.01) the percentage of CH4 in total gas and dissolved-CH4 (dCH4) in dissolved gas. Addition of monensin reduced (P < 0.01) disappearance of nutrients, improved fermentation efficiency and reduced CH4 and H2 emissions. Total microbial nitrogen production was decreased (P < 0.05) but the proportion of feed particle associated (FPA) bacteria was increased with FlaH and monensin supplementation. Numbers of OTUs and Shannon diversity indices of FPA microbial community were unaffected by AlcH and FlaH; whereas both indices were reduced (P < 0.05) by monensin. Taxonomic analysis revealed no effect of AlcH and FlaH on the relative abundance (RA) of bacteria at phylum level, whereas monensin reduced (P < 0.05) the RA of Firmicutes and Bacteroidetes and enhanced Proteobacteria. Supplementation of FlaH enhanced (P < 0.05) the RA of genus Prevotella, reduced Selenomonas, Shuttleworthia, Bifidobacterium and Dialister as compared to control; monensin reduced (P < 0.05) RA of genus Prevotella but enhaced Succinivibrio.ConclusionsThe supplementation of FlaH in high-grain diets may potentially protect CP and starch from ruminal degradation, without adversely affecting fibre degradation and VFA profiles. It also showed promising effects on reducing CH4 production by suppressing H2 production. Protein enzymatic hydrolysates from BSG using flavourzyme showed potential application to high value-added bio-products.

Effects of post-pyrolysis treated biochars on methane production, ruminal fermentation, and rumen microbiota of a silage-based diet in an artificial rumen system (RUSITEC)

This study investigated the effects of including biochars, which differed in post-pyrolysis treatment, on nutrient disappearance, total gas and methane (CH4) emissions, rumen fermentation, microbial protein synthesis and rumen microbiota in an artificial rumen system (RUSITEC) fed a barley silage-based diet. The basal diet contained (g/kg dry matter (DM) basis); 600 barley silage, 270 barley grain, 100 canola meal and 30 mineral/vitamin supplement. Three spruced-based biochars were treated post-pyrolysis with either zinc chloride, a hydrochloric acid/nitric acid mixture or sulfuric acid and each included at 20 g/kg of diet DM. Treatments were assigned to sixteen fermenters (n = 4/treatment) in two RUSITEC units in a randomized complete block design. The experiment was conducted over 15 d, with 8 d of adaptation and 7 d of sampling and data collection. Nutrient disappearance of DM, organic matter (OM), acid detergent fiber (ADF), nutrient detergent fiber (NDF) and starch were determined after 48 h of incubation from d 9–12, and microbial protein synthesis was measured from d 14−15. Data were analyzed using PROC MIXED in SAS, with fixed effects of treatment and day of sampling (repeated measure) and random effects of RUSITEC unit and fermenters. Biochar inclusion did not affect disappearance of DM (P = 0.49), OM (P = 0.60), CP (P = 0.47), NDF (P = 0.48), ADF (P = 0.11) or starch (P = 0.58). Moreover, biochar inclusion did not affect total gas production (P = 0.31) or CH4 produced expressed as mg/g of DM incubated (P = 0.74), and mg/g (P = 0.64), or mg/d (P = 0.70) of DM disappeared. Compared to the control, there was a tendency (P = 0.06) for reduced CH4 production with biochar inclusion when CH4 was expressed as percent of total gas produced. Biochar inclusion did not affect total VFA (P = 0.56) or NH3-N (P = 0.20) production. Microbial protein synthesis was not affected by biochar inclusion (P > 0.05). Total protozoa counts were also unaffected by biochar (P = 0.37) nor did it impact (P > 0.05) the alpha or beta diversity of bacterial populations. In conclusion, the biochars evaluated in this study appeared to have little to no impact on nutrient disappearance, total gas and CH4 production, rumen fermentation, and rumen microbiota in the RUSITEC system.

PSXI-15 Effects of post-pyrolysis treated biochars on nutrient disappearance, methane production and ruminal fermentation of a silage-based diet in an artificial rumen system (RUSITEC)

Abstract This study investigated the effects of post-pyrolysis treated biochar on nutrient disappearance, total gas and methane (CH4) production, rumen fermentation and microbial protein synthesis in an artificial rumen system (RUSITEC) fed a barley silage-based diet. The basal diet consisted of 60% barley silage, 27% barley grain, 10% canola meal and 3% mineral/vitamin supplement (DM basis). Three spruced-based biochars, treated post-pyrolysis with either zinc chloride, hydrochloric acid/nitric acid mixture or sulfuric acid were added at 2.0% of substrate DM. In a randomized complete block design, treatments were assigned to sixteen vessels (n = 4/treatment) in two RUSITEC systems. The experiment was conducted over 15 d, with 8 d of adaptation and 7 d of sampling. Nutrient disappearance of dry matter (DM), organic matter (OM), acid detergent fiber (ADF) and neutral detergent fiber (NDF) was determined after 48 h of incubation from d 9 to 12, and microbial protein synthesis was measured from d 13–15. Data were analyzed using PROC MIXED in SAS, with the fixed effect of treatment and random effect of RUSITEC system and vessel. Biochar inclusion did not affect disappearance of DM (P = 0.49), OM (P = 0.60), CP (P = 0.14), NDF (P = 0.48), ADF (P = 0.11) or starch (P = 0.58). Biochar also had no effect on total gas production (P = 0.31) or CH4 produced expressed as a % of total gas production (P = 0.06), mg/d (P = 0.70), mg/g of DM incubated (P = 0.74), or mg/g of DM digested (P = 0.64). No effect on total VFA (P = 0.56) or NH3-N (P = 0.20) production were observed. Neither microbial protein synthesis nor total protozoa count were affected by biochar addition (P &amp;gt; 0.05). In conclusion, biochar inclusion in a silage-based diet did not exhibit the potential to mitigate CH4 emissions or improve digestion in a RUSITEC system.

A comparative study of artificial cow and sheep rumen fermentation of corn straw and food waste: Batch and continuous operation

To optimize the artificial rumen microorganism sources and develop a stable artificial rumen system, batch and continuous operation were investigated with corn straw and food waste as substrates. The batch trials evaluated the volatile fatty acid (VFA) yield, biogas production, and lignocellulose degradation efficiency. The continuous test evaluated the performance of the artificial cow and sheep rumen systems using a dynamic membrane bioreactor (DMBR) with a stepwise organic loading rate at mesophilic temperature. The anaerobic digestion (AD) of the lignocellulose biomass after rumen fermentation pretreatment and of the permeate from the artificial rumen system were also evaluated for CH4 production. The results indicated that the cow rumen microorganisms were more suitable than sheep rumen microorganisms for lignocellulosic biomass pretreatment and maximized the CH4 yield through the AD process without inhibition. After approximately four months of continuous operation, a stable and continuous artificial rumen system for lignocellulosic biomass degradation was achieved with cow rumen fluid as inoculum. Based on analysis of the core lignocellulose-degrading enzyme levels and gel filtration chromatography, the cow rumen microorganisms could secrete more extracellular multienzyme complexes to hydrolyze lignocellulosic biomass than the sheep rumen microorganisms in vitro. During the batch and continuous operations, a high diversity and similar richness of bacteria and fungi demonstrated that the cow rumen microorganisms can be used as a preferred inoculum for the artificial rumen system. The use of an artificial cow rumen system with a DMBR is a promising way to construct a stable and continuous artificial rumen system to biodegrade lignocellulosic biomass for biogas production.

Effect of combinations of feed-grade urea and slow-release urea in a finishing beef diet on fermentation in an artificial rumen system.

This study evaluated the effect of combinations of feed-grade urea and slow-release urea (SRU) on fermentation and microbial protein synthesis within two artificial rumens (Rusitec) fed a finishing concentrate diet. The experiment was a completely randomized, dose-response design with SRU substituted at levels of 0% (control), 0.5%, 1%, or 1.75% of dry matter (DM) in place of feed-grade urea, with four replicate fermenters per dosage. The diet consisted of 90% concentrate and 10% forage (DM basis). The experiment was conducted over 15 d, with 8 d of adaptation and 7 d of sampling. Dry matter and organic matter disappearances were determined after 48 h of incubation from day 9 to 12, and daily ammonia (NH3) and volatile fatty acid (VFA) production were measured from day 9 to 12. Microbial protein synthesis was determined on days 13-15. Increasing the level of SRU quadratically affected total VFA (Q, P = 0.031) and ammonia (Q, P = 0.034), with a linear increment in acetate (L, P = 0.01) and isovalerate (L, P = 0.05) and reduction in butyrate (L, P = 0.05). Disappearance of neutral detergent fiber (NDF) and acid detergent fiber (ADF) was quadratically affected by levels of SRU, plateauing at 1% SRU. Inclusion of 1% SRU resulted in the highest amount of microbial nitrogen associated with feed particles (Q, P = 0.037). Responses in the efficiency of microbial protein synthesis fluctuated (L, P = 0.002; Q, P = 0.001) and were the highest for 1% SRU. In general, the result of this study showed that 1% SRU in combination with 0.6% urea increased NDF and ADF digestibility and total volatile fatty acid (TVFA) production.

82 Effect of by-product feed supplementation of a hay-based diet on rumen fermentation, diet digestibility, methane production and protozoal population in an artificial rumen (RUSITEC)

Abstract This study investigated the effects of adding sunflower screenings, flax screenings and quinoa to a hay-based diet on ruminal fermentation, DM digestibility (DMD) and enteric methane (CH4) production in an artificial rumen system (RUSITEC). The experiment was a RCBD with 4 treatments assigned to 16 fermentation vessels (n = 4/treatment) in 2 RUSITEC apparatuses. The control diet was 100% hay, with treatments consisting of sunflower screenings, flax screenings and quinoa dockage at inclusion rates of 1.10, 1.38, and 1.59 g DM, respectively. The study period was 15 d, with an 8-d adaptation and 7-d sample collection period. Data were analyzed using the PROC MIXED procedure of SAS with fixed effects of treatment, day of sampling and their interaction as fixed effects. Compared to control, the addition of sunflower screenings decreased (P = 0.020) CH4produced per g of DM digested (10.43 vs. 7.88 mg/g DMD). Inclusion of sunflower screenings reduced (P &amp;lt; 0.01) DMD (67.6 vs. 57.8 %) and the number of protozoa (2.2x104vs. 1x103ml) compared to the control. The addition of flax screenings versus the control diet increased (P = 0.001) CH4produced per g of DMD (10.43 vs. 15.05 mg/g). However, inclusion of flax screenings resulted in a decrease (P &amp;lt; 0.05) in DMD and number of protozoa compared to the control (1.07x103vs. 2.2x104ml, 64.33 vs. 67.64 %, respectively). The addition of flax screenings decreased DMD (P = 0.04). Quinoa inclusion had no effect on DMD or protozoa count, while CH4production increased (P = 0.0003) compared to the control (15.15 vs 10.43 mg/g DMD). Disappearance of NDF did not differ between treatments (P = 0.72). Inclusion of sunflower screenings and quinoa did not affect molar proportions of propionate or and butyrate, while decreased (P &amp;lt; 0.05) by adding flax screenings. In conclusion, the addition of sunflower screenings provided the greatest potential to reduce CH4 emissions associated with supplemented hay-based diets.

Effect of exogenous fibrolytic enzymes and ammonia fiber expansion on the fermentation of wheat straw in an artificial rumen system (RUSITEC)1.

This study investigated the effect of treatment of wheat straw using ammonia fiber expansion (AFEX) and exogenous fibrolytic enzymes (Viscozyme) on fiber digestibility, rumen fermentation, microbial protein synthesis, and microbial populations in an artificial rumen system [Rumen Simulation Technique (RUSITEC)]. Four treatments were assigned to 16 vessels (4 per treatment) in 2 RUSITEC apparatuses in a randomized block design. Treatments were arranged as a 2 × 2 factorial using untreated or AFEX-treated wheat straw with or without exogenous fibrolytic enzymes [0 or 500 μg of protein/g straw dry matter (DM)]. Fibrolytic enzymes were applied to straw, prior to sealing in nylon bags. The concentrate mixture was provided in a separate bag within each fermentation vessel. The RUSITECs were adapted for 8 d and disappearance of DM, neutral detergent fiber (NDF), acid detergent fiber (ADF), and crude protein (CP) was measured after 48 h of incubation. Ammonia fiber expansion increased (P < 0.01) the disappearance of wheat straw DM (69.6 vs. 38.3%), NDF (65.6 vs. 36.8%), ADF (61.4 vs. 36.0%), and CP (68.3 vs. 24.0%). Total dietary DM, organic matter (OM), and NDF disappearance was also increased (P ≤ 0.05) by enzymes. Total microbial protein production was greater (P < 0.01) for AFEX-treated (72.9 mg/d) than untreated straw (63.1 mg/d). Total gas and methane (CH4) production (P < 0.01) were also greater for AFEX-treated wheat straw than untreated straw, with a tendency for total gas to increase (P = 0.06) with enzymes. Ammonia fiber expansion increased (P < 0.01) total volatile fatty acid (VFA) production and the molar proportion of propionate, while it decreased (P < 0.01) acetate and the acetate-to-propionate ratio. The AFEX-treated straw had lower relative quantities of fungi, methanogens, and Fibrobacter succinogenes (P < 0.01) and fewer protozoa (P < 0.01) compared to untreated straw. The pH of fermenters fed AFEX-treated straw was lower (P < 0.01) than those fed untreated straw. Both AFEX (P < 0.01) and enzymes (P = 0.02) decreased xylanase activity. There was an enzyme × straw interaction (P = 0.02) for endoglucanase activity. Enzymes increased endoglucanase activity of AFEX-treated wheat straw, but had no effect on untreated straw. The addition of enzymes lowered the relative abundance of Ruminococcus flavefaciens, but increased F. succinogenes. These results indicate that AFEX increased the ruminal disappearance of wheat straw and improved fermentation and microbial protein synthesis in the RUSITEC.

Effect of engineered biocarbon on rumen fermentation, microbial protein synthesis, and methane production in an artificial rumen (RUSITEC) fed a high forage diet.

The objective of this study was to investigate the effects of adding engineered biocarbon to a high-forage diet on ruminal fermentation, nutrient digestion, and enteric methane (CH4) production in a semi-continuous culture artificial rumen system (RUSITEC). The experiment was a completely randomized block design with four treatments assigned to sixteen fermentation vessels (four/treatment) in two RUSITEC apparatuses. The basal diet consisted of 60% barley silage, 27% barley grain, 10% canola meal, and 3% supplement (DM basis) with biocarbon added at 0, 0.5, 1, and 2% of substrate DM. The study period was 17 d, with a 10-d adaptation and 7-d sample collection period. Increasing biocarbon linearly increased (P < 0.05) disappearance of DM, OM, CP, ADF and NDF. Compared to control, increasing biocarbon enhanced (P < 0.01) production of total VFA, acetate, propionate, branch-chained VFAs, and tended to increase (P = 0.06) NH3-N. Microbial protein synthesis linearly increased (P = 0.01) with increasing biocarbon. Addition of biocarbon reduced overall CH4 production compared with the control (P ≤ 0.05). There were no differences (P > 0.05) in production of total gas, large or small peptides, or in the number of protozoa as a result of addition of biocarbon to the diet. Addition of biocarbon to a forage diet increased DM digestibility by up to 2%, while lowering enteric CH4 production and enhancing microbial protein synthesis in in vitro semi- continuous culture fermenters.

Effects of hop varieties on ruminal fermentation and bacterial community in an artificial rumen (rusitec)

There is a growing interest in the use of hops (Humulus lupulus) as an alternative to antibiotics to manipulate ruminal fermentation. However, the effects of different hop varieties on ruminal fermentation and bacterial populations have not been studied. Here the effects of three hop varieties, Cascade (CAS), Millennium (MIL) and Teamaker (TM), at a level of 800 µg mL(-1) inoculum on ruminal fermentation and microbial populations in an artificial rumen system (rusitec) fed a barley silage-based total mixed ration were investigated. Bacterial populations were assessed using real-time polymerase chain reaction and expressed as a percentage of total bacterial 16S rRNA gene copies. All hops reduced (P < 0.001) total gas, methane and the acetate:propionate ratio. Liquid-associated Fibrobacter succinogenes, Ruminococcus albus and Streptococcus bovis were reduced (P < 0.05) by MIL and TM. Feed particle-associated S. bovis was reduced (P < 0.01) by MIL and TM, but TM and CAS increased (P < 0.01) Ruminobacter amylophilus and Prevotella bryantii respectively. Methanogens were decreased (P < 0.05) by MIL in both liquid and solid fractions and by CAS in the solid fraction. The total amount of α- and β-acids in hops affected the ruminal fermentation. Hop-induced changes in fermentation and microbial populations may improve energy efficiency use in the rumen. Further research is needed to determine the effects of hops on in vivo ruminal fermentation, microbial populations and animal performance.

Fermentation patterns and nutrient contents of forb-containing silages and their effects on microbial fermentation in the artificial rumen system RUSITEC

SUMMARYGrassland forbs are important constituents of swards under low-input management. The hypothesis tested was that herbage from unfertilized swards consisting of a mixture of perennial ryegrass (Lolium perenne), white clover (Trifolium repens), dandelion (Taraxacum officinale) and ribwort (Plantago lanceolata) (treatment GCF) would exert a significant effect on the composition and quality of silage for rumen microbes compared with herbage from nitrogen-fertilized (50 kg N/ha/cut) pure ryegrass swards (treatment GN) or unfertilized ryegrass white clover swards (treatment GC). GCF had average proportions of clover and forb of 0·21 and 0·58, respectively. The crude protein and fibre fractions declined and non-fibrous carbohydrates (NFC) increased from GN over GC to GCF. Irrespective of cutting date (spring and summer), GN showed extremely high ammonia (NH3) concentrations, whereas GCF resulted in the highest concentrations of lactic acid coinciding with the lowest contents of butyric acid and ethanol. The ratios between the soluble and less soluble N fractions decreased in the order GN&gt;GC&gt;GCF. A similar sequence was observed in RUSITEC for the apparent disappearance rates of crude protein and fibre fractions. The concentration of NH3-N in the fermenter fluid declined in the order GN&gt;GC&gt;GCF. GCF produced less short-chain fatty acids (SCFA) than GN and GC. Microbial nitrogen (MN) flow was not significantly different between treatments but tended to decline in the order GN&gt;GC&gt;GCF, whereas the proportion of MN originating from NH3-N increased inversely. The efficiency of microbial protein synthesis was unaffected by the different silages. It is concluded that forb-rich swards are suitable for the preparation of high quality silages. There is a need for further investigation into postruminal availability and suitable supplementation for such silages in order to fully exploit their potential for improving the efficiency of nitrogen utilization in ruminant nutrition.

Effect of adding caprylic and capric acid to grass on fermentation characteristics during ensiling and in the artificial rumen system RUSITEC

Silage was prepared from grass that was treated either with caprylic or capric acid, prior to ensiling, to increase aerobic stability. The silage was introduced to the RUSITEC in order to measure the effect of treatment on in vitro microbial metabolism. Although, caprylic acid inhibited lactic acid formation during the ensiling process, aerobic stability was high. Capric acid did not interfere with lactic acid production yielding silage with moderate stability. In RUSITEC neither caprylic nor capric acid had an effect on protozoa counts, but both lowered apparently degraded organic matter (OMAD). Caprylic acid promoted methane and acetate production while propionate production and microbial yield were lower. Capric acid had no effect on the production of methane, acetate and propionate; butyrate production increased and microbial yield remained unaffected. Caprylic and capric acid are highly preservative, yielding silage of good quality and high aerobic stability indicating their efficiency against spoilage micro-organisms. The bactericidal effect however, was modified during the ensiling process since both lost some toxicity against rumen protozoa and methanogenic bacteria. Net production of rumen microbial cell mass per unit OMAD was not impaired.

Lipid-induced depression of methane production and digestibility in the artificial rumen system (RUSITEC)

An artificial rumen (RUSITEC) equipped with eight fermenters was used to examine the effects of canola oil (CA), cod liver oil (CD) and coconut oil (CO) on methane production, dietary digestibility and rumen microbial populations. The experiment, repeated three times, involved two diets (100% grass hay or a 90%:10% wheat:hay mixture) either untreated (controls) or sprayed with CA, CD or CO (10%, wt/wt) in a 2 × 4 factorial arrangement. Dry matter disappearance and CH4 production were greater (P &lt; 0.05) from untreated concentrate diet than from untreated hay. There were significant interactions (P &lt; 0.05) between diet and lipid type for DM digestion and several of the fermentation parameters. Coconut oil decreased (P &lt; 0.05) DM and neutral detergent fibre disappearance of hay but did not affect digestion of concentrate. All oils, especially CO, depressed (P &lt; 0.05) CH4 production (mmol g−1 digestible DM) and methanogenic populations regardless of diet. Methanogens on CO-treated diets numbered less than 1% of those on CA- and CD-treated diets. Total viable, amylolytic, and cellulolytic bacterial numbers were also substantially reduced (P &lt; 0.05) by CO, but not by CA or CD for both diets. Bacterial colonization and digestion of CO-treated hay was markedly less extensive than that observed on untreated, CA- or CD-treated hay. The molar proportion of propionate produced was increased (P &lt; 0.05) by CA and CD, for the hay diet, but not for the concentrate diet. Coconut oil decreased (P &lt; 0.05) the molar proportion of propionate produced on the hay diet and increased (P &lt; 0.05) it on the concentrate diet. Of the three oils, CO was most inhibitory to CH4 production and depressed fibre digestion. The CA and CD also decreased CH4 production, but did not affect feed digestion in either diet. Consequently, the amount of metabolizable energy of feeds may be increased when diets are supplemented with these oils. Key words: Lipids, methane, digestibility, artificial rumen, bacteria, VFA

Characteristics of white-rotted woody materials obtained from Shiitake mushroom ( Lentinus edodes) and nameko mushroom ( Pholiota nameko) cultivation with in vitro rumen fermentation

The characteristics of digestion of white-rotted woody materials, obtained in the cultivation of shiitake mushroom ( Lentinus edodes) and nameko mushroom ( Pholiota nameko) were studied using a batch artificial rumen system. The time course changes in digestibilities of dry matter and cell wall, gas production, volatile fatty acids (VFA) production, NH 3-N concentration and pH values were measured as parameters during fermentation by rumen microorganisms. In the white-rotted woody materials, the pattern of the time course changes in every parameter came near to that of rice straw used as the control material. Through the process of white-rot by two fungi, the white-rotted woody materials had a longer lag phase at the beginning of rumen fermentation. In evaluating the nutritive value of white-rotted materials, VFA production or gas production can be used as appropriate criteria in combination with in vitro digestibility by Tilley and Terry's procedure.

Degradation of L‐5‐vinyloxazolidine‐2‐thione, a goitrogenic product from rapeseed, by rumen microorganisms

Abstract The use of rapeseed meal for animal feeding is limited by the presence of antinutritional compounds, such as glucosinolates. An in vitro rumen system was used to test the effect of L‐5‐vinyloxazolidine‐2‐thione (VOT), a toxic hydrolysis product from glucosinolates found in rapeseed. The effect of VOT on rumen performance was minimal. The VOT was degraded efficiently (60–70%) in the artificial rumen system, when rape‐seed was fed batchwise at 20% (w/w) of the diet. The degradation of VOT is caused by bacteria because the addition of the (oil containing) rapeseed resulted in a disappearance of ciliated protozoa. Experiments with pure VOT resulted in complete degradation both in batch (2 mM) and in continuous culture (4 mM).

Effect of the level of feeding on the digestion of hay and carbohydrase activities in an artificial rumen

In two separate experiments, the effects of four and two (in duplicate) levels of feeding on the digestion of hay in an artificial rumen system (RUSITEC) were determined by measuring overall digestibility, short chain fatty acid production, gas production, various glycoside hydrolase activities, and hemicellulase activity. The level of feeding, which varied by up to a factor of four, had no effect on the overall digestibility of the hay. Increasing the level of feeding by a factor of four gave an approximately fourfold increase in the production of acetic, propionic, and butyric acids. It took about 2 days to attain these higher productions. The same increase in feed also gave an approximately fourfold increase in methane and carbon dioxide production, but the increase, especially in methane, was not fully sustained. The different levels of feeding had no effect on the activities of α- and β- d- glucopyranosidase , β- d- xylopyranosidase , and α- and β- d- galactopyranosidase . A fourfold increase in the level of feeding increased the hemicellulase activity by a factor of approximately two.

Inhibition of methanogenesis by DDT.

Methanobacterium strain M.o.H. is a strict, anaerobic methane-forming bacterium which obtains its energy from the oxidation of hydrogen; the electrons generated are passed to CO2 which is reduced to CH4. Inhibition of CH4 biosynthesis by alkyl halides was first documented by Bauchop1 who reported that the addition of carbon tetrachloride, chloroform or methylene chloride to rumen fluid inhibited CH4 production and increased H2 production. Rufener and Wolin2 reported similar findings in an artificial rumen system. Van Nevel3 described the inhibitory effects of chloral hydrate on CH4 formation in sheep rumen fluid incubated in vitro and in vivo. These observations were extended by Wood4 who described the inhibitory effects of chloroform, dichloromethane, methylene chloride and propyl iodide on CH4 formation in cell extracts of Methanobacterium omelianskii. Photolysis was observed to reverse inhibition. The site of action of these compounds has not been identified, but the reversal of inhibition by light was taken as evidence that the site is a B12 complex involved in the final transmethylation reactions which lead to CH4 synthesis4. The similarity between chloroform and the active centre of 1,1,1,trichloro-2,2 bis p-chlorophenyl ethane (DDT) raised the possibility that this pesticide might also inhibit methane biosynthesis.