Fungal pretreatment of wheat straw: Effects on the biodegradability of cell walls,structural polysaccharides,lignin and phenolic acids by rumen microorganisms

Disappearance of cell wall components of untreated straw and straw treated with the ligninolytic white-rot fungi Phanerochaete chrysosporium, Dichomitus squalens and Cyathus stercoreus were determined during the course of rumen digestion of samples in nylon bags. The first fungus degraded hemicelluloses and cellulose non-selectively, adversely affecting the digestion rate of crude cell walls. Dichomitus squalens and C. stercoreus preferentially degraded hemicelluloses and lignin, affording cell wall degradation rates 1.5 times higher than in native straw. Furthermore, the extent of cell wall digestion was also significantly enhanced. Both strains improved the extent of cellulose digestion, whereas the potentially degradable xylan fraction remained unchanged. Polysaccharide digestion rates were influenced in different ways depending on the strain tested: straw degraded by C. stercoreus showed an increase in cellulose digestion rate by 50%, whereas residual arabinose units were slowly degraded. Xylan was degraded 1.8 times faster in straw decayed' by D. squalens, while cellulose digestion remained unchanged. Phanerochaete chrysosporium depressed both xylan and cellulose digestion rates. Fungal-treated lignins were solubilised in the rumen faster than in untreated straw, whereas only treatment by C. stercoreus resulted in higher lignin losses. Esterified phenolic acids were extensively degraded by all three fungi. Residual ferulic and p-coumaric acids accumulated during rumen digestion, although only the former decreased in the original straw.     

Determination of phenolic acids in plant cell walls by microwave digestion

Microwave digestion (750 W for 90 s) with 4 M NaOH was used to release esterified and etherified hydroxycinnamic acids from cell walls of maize (Zea mays L), wheat (Triticum aestivum L), barley (Hordeum vulgare L) and oilseed rape (Brassica napus L) stems. Subtraction of values for saponifiable phenolic acids obtained after treatment with I M NaOH at room temperature from digest results provided a measure of β-ether linked units. These were exclusively (E + Z)-ferulic acid in the cereal straws. Only trace amounts of ether- and ester-linked hydroxycinnamic acids were released from the dicotyledon, ripe straw. Microwave digestion was shown to be an order of magnitude more effective than dioxane-HCl at liberating β-ether bound phenolic acids and as effective, but substantially quicker, than previously described high-temperature alkaline digestions.     

Uptake of small neutral peptides by mixed rumen microorganisms in vitro

The metabolism of a range of neutral di- and oligopeptides and peptide p-nitroanilides was investigated in strained ruminal fluid diluted with anaerobic buffer. Peptide uptake was assayed by decrease in fluorescamine-reactive material in extracellular fluid, and peptide p-nitroanilide hydrolysis by diazotisation of the released p-nitroaniline. Addition of glucose and dithiothreitol did not alter uptake of di- or trialanine. Calculated V_max for di- and trialanine uptake were 1.4 and 1.9 nmol min^?1 mg DM^?1, corresponding K_m were 0.30 and 0.14 mmol litre^?1. Dipeptide uptake was 0.72 to 0.90 nmol min^?1 mg DM^?1, except for glycylproline, which was taken up at 0.43 nmol min^?1 mg DM^?1. There was a wider range for tripeptide uptake (0.5 to 1.6 nmol min^?1 mg DM^?1), with trialanine being taken up most rapidly. Tetra- and pentaalanine were removed at 0.93 and 0.71 nmol min^?1 mg DM^?1. Uptake of amino acid residues as alanine oligopeptides was two to three times more rapid than uptake as dialanine. These data suggest that peptides would accumulate in rumen fluid during hydrolysis of rapidly degraded proteins, but peptide uptake would exceed rate of release from more slowly degraded proteins. Rates of hydrolysis of eight peptide p-nitroanilides were 0.56 to 1.53 nmol min^?1 mg DM^?1, and were of similar magnitude to uptake of di- and tripeptides; proline-containing p-nitroanilides were also more slowly metabolised.     

Mode of action of yeast culture (YEA-SACC 1026) for stimulation of rumen fermentation in buffalo calves

The effect of daily supplementation of 5 g Saccharomyces cerevisiae yeast culture (YC, YEA-SACC 1026), 30 g NaHCO₃, supernatant from 5 g YC (YCS), 5 g autoclaved YC (YCH) or 5 g γ-irradiated YC (YCR) to the diet of buffalo calves on rumen microbial populations and fermentation pattern was examined. Addition of 30 g NaHCO₃ increased the rumen pH to the level observed with YC group. The pH and the concentrations of total, total viable and cellulolytic bacteria and total volatile fatty acids (VFA) were significantly higher while that of lactic acid, hexose-unit oligosaccharides and NH₃-N were significantly lower in the rumen fluid of YC compared with the control group. The effect of NaHCO₃ was 39·5 and 59·5% in decreasing the concentrations of lactic acid and hexose-unit oligosaccharides, 48·1, 47·2 and 45·5% in increasing the numbers of total, total viable and cellulolytic bacteria, 50·0 and 58·1% in increasing the concentrations of total VFA and protein and 51·3% in decreasing the concentration of NH₃-N of YC. The corresponding values for YCR addition in the diet were 38·6, 45·7, 48·5, 44·4, 51·5, 39·1, 48·1 and 46·5%. The effect of YCS and YCH was only marginal, but conspicuous up to 2 h after feeding, in changing the above rumen variables when compared with the YC group. The results indicated that contribution of increase in pH in changing the rumen variables was approximately 50% of YC and almost all the stimulatory activity was associated with live yeast cells. Autoclaving of YC destroyed almost all and γ-irradiation of YC retained about 50% of stimulatory activity of YC. The effect of YC on rumen fermentation, which was maximum up to 2 to 4 h after feeding, decreased with time. © 1998 SCI.     

Gel filtration studies of peptide metabolism by rumen microorganisms

Peptide metabolism by rumen microorganisms was investigated by gel filtration using Sephadex G-25 with water as eluant. Protein hydrolysates containing a mixture of peptides were used to calibrate the column. Total peptide in each fraction was estimated from its A₂₀₆, and free peptide amino groups were analysed by fluorescamine, thus enabling the average peptide M_r to be calculated. Three different protein hydrolysates produced similar, nearly linear, relations between log M_r and elution volume for peptides between 300 and 2000 Da. Trypticase, a pancreatic hydrolysate of casein, was metabolised rapidly in rumen fluid in vitro. Hydrolysis appeared to be complete after 6 h, leaving a small residual peptide concentration which persisted up to 24 h, equivalent to about 15% of the original peptide concentration of 2 g litre^?1. Residual peptides from casein hydrolysis were 0.05 g litre^?1 at 24 h. Peptides accumulated in rumen fluid of sheep receiving dietary ionophores. Two hours after feeding, the accumulation with monensin appeared to be of peptides of a wide M_r range, while tetronasin caused an accumulation mainly of smaller, <570 Da, peptides. Treatment of Trypticase with acetic anhydride afforded 76% protection of its peptides from degradation to ammonia in a 6-h incubation. When Trypticase was fractionated by gel filtration then acetylated, none of the fractions was protected significantly better than others.     

Effects of Cordyceps militaris on the growth of rumen microorganisms and in vitro rumen fermentation with respect to methane emissions

This experiment was designed to investigate the effects of different concentrations (0.00, 0.10, 0.15, 0.20, 0.25, and 0.30 g/L) of dried Cordyceps militaris mushroom on in vitro anaerobic ruminal microbe fermentation and methane production using soluble starch as a substrate. Ruminal fluids were collected from Korean native cattle, mixed with phosphate buffer (1:2), and incubated anaerobically at 38°C for 3, 6, 9, 12, 24, 36, 48, and 72 h. The addition of C. militaris significantly increased total volatile fatty acid and total gas production. The molar proportion of acetate was decreased and that of propionate was increased, with a corresponding decrease in the acetate:propionate ratio. As the concentration of C. militaris increased from 0.10 to 0.30 g/L, methane and hydrogen production decreased. The decrease in methane accumulation relative to the control was 14.1, 22.0, 24.9, 39.7, and 40.9% for the 0.10, 0.15, 0.20, 0.25, and 0.30 g/L treatments, respectively. Ammonia-N concentration and numbers of live protozoa decreased linearly with increasing concentrations of C. militaris. The pH of the medium significantly decreased at the highest level of C. militaris compared with the control. In conclusion, C. militaris stimulated mixed ruminal microorganism fermentation and inhibited methane production in vitro. Therefore, C. militaris could be developed as a novel compound for antimethanogenesis.     

Comparison of releasing bound phenolic acids from wheat bran by fermentation of three Aspergillus species

Wheat bran was fermented at 28 °C for 7 days under 70% humidity by Aspergillus niger, Aspergillus oryzae and Aspergillus awamori. Total phenolic content (TPC) of the unfermented sample was 1531.5 μg g^?1 wheat bran. After the fermentation of Aspergillus awamori, Aspergillus oryzae and Aspergillus niger, TPC reached 5362.1, 7462.6 and 10 707.5 μg g^?1, respectively. The antioxidant activity in the extractions of fermented wheat bran also increased significantly compared with the unfermented sample (P < 0.05). Aspergillus niger showed the greatest capacity to release bound ferulic acid (416.6 μg g^?1). Aspergillus oryzae and Aspergillus awamori had the advantages of releasing more chlorogenic acid (84.0 μg g^?1) and syringic acid (142.3 μg g^?1), respectively. The destructive effect of Aspergillus niger on wheat bran structure was the strongest, followed by that of Aspergillus oryzae. This effect of Aspergillus niger may be due to its higher cellulase, xylanase, arabinofuranosidase and β‐xylosidase activities. Besides, Aspergillus oryzae possessed higher β‐glucosidase activity, and Aspergillus awamori had higher α‐amylase and feruloyl esterase activities. Aspergillus niger may be the best to release bound phenolic acids in the three Aspergillus species. These will provide the helpful information for understanding mechanism of the fermentation by Aspergillus species releasing bound phenolic in wheat bran.     

The phenolic acid and polysaccharide composition of cell walls of bran layers of mature wheat (Triticum aestivum L. cv. Avalon) grains

The purpose of this study was to examine the carbohydrate and phenolic‐ester composition of cell walls in wheat bran layers. Four defined layers of wheat bran were separated manually from mature grains of wheat (Triticum aestivum L. cv. Avalon) to give samples of beeswing bran (outer pericarp), cross cells, testa + nucellar epidermis and aleurone cells. The cell‐wall material from each layer, and from a sample of intact bran, was analysed for carbohydrates and wall‐bound esterified phenolic acids. The cell‐wall material of intact bran was rich in arabinose and xylose with significant quantities of glucose and uronic acid and a relatively small amount of galactose and mannose. The varying ratios of arabinose:xylose in cell walls of isolated bran layers indicated that the heteroxylans had tissue‐specific substitution patterns. HPLC analysis of phenolic acids identified significant amounts of esterified ferulic acid and 8‐8′‐ (aryltetralin form), 5‐8′‐, 5‐5′‐, 8‐0‐4′‐ and 5‐8′‐(benzofuran form)‐dehydrodiferulic acids in the isolated cell walls. Ferulic acid was highly concentrated in the aleurone layer, whereas dehydrodiferulates were concentrated in the beeswing bran and cross cells. The role of phenolic cross‐linking is discussed in relation to the architecture of the cell walls of wheat bran and to processing implications. Copyright © 2005 Society of Chemical Industry     

Metabolism of dietary (Acetyl-1-14c)-plant cell walls in the rat intestine

To determine a fate of acetyl groups in intact dietary plant cell walls (PCW) spinach cells were labelled using [1-¹⁴C]acetate as a precursor and the PCW isolated. The (acetyl-¹⁴C)-PCW were fed to rats by garage and the ¹⁴C traced in the rat gut and in the body tissues and excreta of the rat. Some label was solubilised during passage through the upper intestine of the rat, and subsequently incorporated into the body tissues of the rat. A small amount of the radioactivity was excreted as CO₂ (4%) and in urine (<1%). (Acetyl-¹⁴C)-PCW which reached the caecum was solubilised and some [¹⁴C]acetate released. The solubilised ¹⁴C was incorporated in liver tissue mainly as amino acid present in protein.     

Metabolism and fate of dietary (U-14C)-labelled spinach cell walls in the rat

Using uniformly ¹⁴C-labelled spinach (Spinacia oleracea L) plant cell walls (PCW) the metabolism of PCW can be followed in a defined manner in the rat. Only 10% of the ¹⁴C was recoverable in the gut contents and faeces 18 h post-gavage. Two percent of the ¹⁴C was excreted in urine and 25% excreted as CO₂. ¹⁴C was found in all tissues of the body but was most concentrated in the adrenal glands, colon and caecum. The ¹⁴C was also present at moderately high concentration in the liver pelt, and owing to their larger size, these tissues accounted for a high percentage of the total ¹⁴C. In the liver the ¹⁴C was predominantly associated with phospholipid, whereas in the pelt it was present in protein and in fatty acid residues esterified to cholesterol. Dietary PCW material is extensively fermented in the caecum and colon. Also, the products of fermentation are a source of energy and important structural precursors of lipids and proteins for the animal.     

The digestion of monosaccharide residues of the cell walls of oat and vetch hays by rumen contents in vitro

The extent and pattern of digestion of oat hay (Avena sativa L.) and vetch hay (Vicia sativa L.) monosaccharides by rumen contents was studied in vitro. The ratios of matrix polysaccharides to lignin were 1.25:1 and 3.82:1 in the vetch and oat hays, respectively. Glucose, xylose and uronic acids were the main sugars in both plants, comprising about 90% of the total monosaccharides. Glucose, xylose and arabinose were mainly confined to the cell walls (CW), whereas galactose and uronic acids were found in high proportions in the soluble fraction. Vetch had a particularly high uronic acid content (14.4 g 100 g^?1 DM), of which 71% was pectic material. The ratios of CW-glucose to CW-xylose were 2.23:1 and 3.74:1 in the oat CW and vetch CW, respectively. Based on monosaccharide analyses of the CW material, it is suggested that the degree of branching of the matrix polysaccharides is about twice as high in vetch as in oat hay. Total glucose and xylose were more digestible in oat than in vetch hay, whereas most of the minor sugars and the total uronic acids were more digestible in the vetch. Irrespective of species, CW glucose was more digestible than CW xylose. The digestibilities of CW glucose, CW xylose and CW uronic acid were: 61.0, 55.3, 51.5, 34.3 and 62.7, 42.6 for the oat hay and vetch hay, respectively. Following the pattern of digestion, CW arabinose and CW glucose were digested faster than CW xylose and CW uronic acid, irrespective of plant species. The extent of digestion at 12 h of incubation of these sugars was higher in vetch than in oat hay. It is suggeted that the concentration ratio of rapidly to slowly degradable CW sugars, in a given plant, is a major determinant of the rate of CW digestion by rumen microorganisms.     

Roles of structural phenylpropanoids in forage cell wall digestion

Phenolic constituents (lignins and phenolic acids) and carbohydrates are assembled in a tight architecture which differs according to the plant species. During cell wall digestion, the hydrolysis kinetics differ between carbohydrates and seem to depend chiefly on the content and organisation of tissue phenolics. Among the phenylpropanoids, ferulic acid is released more quickly than p-coumaric acid. Lignins remain largely in the cell walls. They also undergo transformations, chiefly solubilisation as lignin-carbohydrate complexes. The limiting effect of lignins on cell wall degradation increases with increasing content. However, their effect on degradation might also depend on qualitative factors such as lignin structure and polymer organisation in walls and tissues. When various grasses (normal and selected genotypes), or grasses and legumes are compared, correlations between certain factors such as lignin uncondensed fraction, syringyl units or phenolic acids contents and cell wall degradation emerge but not clear causal relationship has been shown. Nonetheless, other structural characteristics, related to the alkali reactivity of lignins, seem to have a stronger influence on cell wall degradation. Phenylpropanoids seem to act mainly as a physical and (bio)chemical barrier to the action of the microbial enzymes. In addition, their reactivity as phenolic compounds and their hydrophobicity seem to play a role. Digestion is not limited only by phenolics. The factors that limit glycanolysis—the accessibility, crystallinity and capillary structure of cellulose and the branching of hemicelluloses—seem to have little or no effect on cell wall degradation in vivo. In contrast, other antiquality substances (tannins, cutin and silica), plant antomy, environmental factors, factors modulating microbial growth and animal physiology influence cell wall utilisation. Future research in this field should focus on the effects of phenolic structure and of cell wall and tissue organisation on carbohydrate degradation.     

Effect of humic acid on fermentation and ciliate protozoan population in rumen fluid of sheep in vitro

BACKGROUND: Humic acid (HA) as a product of decomposition of animal and plant tissue is used in animal production as a feed supplement, antimicrobial product and growth stimulator. The objective of the present in vitro study was to investigate the effects of dietary humic acid as a commercial Humacid 60 Basic (H60B) feed additive preparation on rumen fermentation and the ciliate protozoan population in the rumen fluid of sheep using a high fibre (HF) and high concentrate (HC) diet in batch cultures and artificial rumen (RUSITEC). RESULTS: Production of total volatile fatty acids (VFAs) was significantly decreased (P < 0.001) for batch cultures by the HF‐H60B diet. The HF‐H60B diet decreased ammonia N in RUSITEC (P < 0.001). An increase in the population of Enoploplastron triloricatum, Isotricha spp. and Ophryoscolex c. tricoronatus with the HF‐H60B diet and Diploplastron affine with the HC‐H60B was observed. The H60B did not affect the total ciliate population and Entodinium spp. CONCLUSION: It can be concluded that dietary humic acid preparations are not effective as dietary antiprotozoal agents. Humic acid might enhance microbial growth and energy efficiency in doses up to 10 g kg^?1 DM of diet. Copyright © 2009 Society of Chemical Industry     

14C labelling of lignins of normal and bm3 maizes for fermentation studies

[U-¹⁴C] phenylalanine (phe*) and [O¹⁴CH₃] sinapic acid (sin*) were infused into the cut ends of normal and bm3 maizes (anthesis stage) under or above the last node or at mid-internode, with or without the leaf, in light or in darkness. Radioactivity was measured in the organs, and in phenolic constituents of the cell wall and saponified residues of the bases and tops of the apical inter-node. In both maize genotype labelled under the node the radioactivity was distributed more evenly in the organs with sin* than with phe*. Infusion above the node and at mid-internode greatly increased radioactivity in the bases and tops, respectively. Removal of the leaf only slightly increased the radioactivity, mainly in the bases, and no clear-cut effect of darkness was observed. Phe* labelled the phenolic acids and the three lignin units, but the syringyl units of bm3 maize were only slightly labelled. Sin* specifically labelled the syringyl units, which represented the least condensed fraction of lignins. Both the native and labelled lignins were highly alkali soluble. There were differences in lignin biogenesis between the bases and tops, and between normal and bm3 maizes. The newly formed lignins were slightly different from the native lignins but had similar types of heterogeneity, with variations in the internode and between genotypes similar to those in native lignins. Provided due allowance is made for the distinguishing characteristics of newly formed lignins, the [¹⁴C-lignin] cell walls, which are strongly labelled on complementary structures, seem suitable model substrates for fermentation studies.     

Degradation of condensed tannins by rumen microbes exposed to quebracho tannins (QT) in rumen simulation technique (RUSITEC) and effects of QT on fermentative processes in the RUSITEC

In an earlier study it was observed that the rumen microbes from cattle which had never consumed tannin-containing diets do not have enzymes for degrading condensed tannins. In this study, rumen microbes were exposed to small amounts of quebracho tannins for 8 days using a rumen simulation technique (RUSITEC). The levels maintained in the RUSITEC were 0.1, 0.2 and 0.4 mg of the spray-dried quebracho powder (SDQT) per ml of the medium. After 8 days of tannin exposure, the liquor containing ‘exposed/adapted’ microbes from RUSITEC was incubated for 40 h without and with purified tannins of quebracho and Dichostachys cinerea leaves in in vitro gas method. There was no degradation of condensed tannins. The enzymes for degradation of condensed tannins were not induced in rumen microbes by exposure to different concentrations of tannins for 8 days in the RUSITEC. In the RUSITEC, SDQT significantly reduced the number of total protozoa, entodiniomorphs and holotrichs; effect was higher on holotrichs. There was no significant change in the levels of short chain fatty acid but the molar proportion of propionate was significantly higher and of butyrate significantly lower at 0.4 mg SDQT ml^?1. Significantly lower levels of ammonia in the medium was also observed on injection of tannins. Microbial mass production, calculated using ¹⁵N incorporation, was similar at 0.1 and 0.2 mg SDQT ml^?1 but significantly lower (13%) at 0.4 mg SDQT ml^?1. The dry matter digestibility of the feed (80% hay and 20% barley) was not significantly affected by SDQT.     

生熟麦曲在黄酒传统工艺中的应用研究

通过对生麦曲、熟麦曲、生麦曲和熟麦曲混合配比按传统黄酒发酵工艺进行试验,得出生麦曲因液化力、糖化力和蛋白质分解力等3个力都较低,使它起发时间迟,发酵缓慢,不彻底;熟麦曲3个力都较高,使其起发时间早,且发酵较彻底;混合曲由于按生麦曲和熟麦曲一定关系配比,表现出其的3个力处于两者之间,发酵状况也处于两者之间,同时得出可以酿造出与生麦曲所酿的酒风味相媲美的酒,为进一步改良传统工艺打下一定基础.混合曲中生麦曲与熟麦曲按9:1的比例较佳.     

Effect of feeding complete feed block containing Prosopis cineraria leaves and polyethylene glycol (PEG)‐6000 on nutrient intake,its utilization,rumen fermentation pattern and rumen enzyme profile in kids

A study was carried out to determine the effect of replacing the cake portion of concentrate mixture with 5 parts polyethylene glycol (PEG)‐6000 in a complete feed block (CFB) containing Prosopis cineraria leaves on the performance, rumen fermentation pattern and rumen enzyme profile of kids under an intensive system of rearing. Eighteen weaners of Sirohi goat of similar body weight (16.0 ± 0.5 kg) and age (90 ± 5 days) were divided into three equal groups. They were housed in individual cages in a side open asbestos roof shed with mud floor. All the kids received CFBs containing 50 parts P cineraria leaves and 50 parts concentrate mixture. CFB offered to the first group had high protein (183.8 g kg^?1; HP), that offered to the second group had low protein (131.3 g kg^?1; LP) and that offered to the third group had low protein (124.7 g kg^?1) but contained PEG‐6000 (LP‐PEG). The concentrate mixtures in LP and LP‐PEG were without groundnut cake, whereas in LP‐PEG, groundnut cake was replaced by barley and 5 parts PEG‐6000 were incorporated. CFBs were similar in their nutritive value except for crude protein (CP). Prosopis leaves utilized in the CFB contained (g kg^?1 dry matter) 129.1 CP, 535.5 neutral detergent fibre, 395.8 acid detergent fibre and 222.8 acid detergent lignin. There were significant differences in dry matter intake (g day^?1) between HP (1102), LP (1108) and LP‐PEG (1194); the trend in Metabolizable energy intake was similar. During the growth trial, LP kids consumed maximum amount of feed (76.91 kg) followed by HP (75.73 kg) and LP‐PEG (73.12 kg). However, maximum feed efficiency (feed consumed kg^?1 live weight gain) was recorded in LP‐PEG kids (9.59) followed by HP (10.64) and LP (11.60). These differences were statistically significant (p < 0.05). Although there was no significant difference in the digestibility of dry matter among the groups, there was significant difference in the digestibility of CP, neutral detergent fibre and acid detergent fibre. The digestibility of CP was 0.591, 0.484 and 0.645, that of neutral detergent fibre was 0.397, 0.308 and 0.499 and that of acid detergent fibre was 0.168, 0.154 and 0.282 in HP, LP and LP‐PEG, respectively. Rumen metabolites studied 6 h after feeding revealed that there were significant (p < 0.05) differences in the concentrations of ammonia N, tri‐chloro acetic acid precipitable N and total volatile fatty acids among the three groups, but not pH. The rumen enzyme concentrations showed significant (p < 0.05) differences for α‐amylase, whereas the differences were non‐significant for CMcase and protease. After 90 days of feeding trial, the maximum weight gain was recorded in LP‐PEG (7.62 kg) followed by HP (7.23 kg) and LP (6.53 kg). It can be concluded that, when kids are reared under an intensive system on complete feed blocks containing Prosopis leaves, high protein concentrate can be replaced with a low protein concentrate containing 5 parts PEG, which would not only alleviate the negative effects of tannin but would also spare expensive groundnut protein. Copyright © 2005 Society of Chemical Industry     

In vitro effects of phlorotannins from Ascophyllum nodosum (brown seaweed) on rumen bacterial populations and fermentation

BACKGROUND: Use of brown algae (seaweed) in ruminant diets is increasing, but the effects of its phlorotannins (PT) on rumen microbial ecology have not been determined. Mixed forage (50:25:25 ground barley silage–alfalfa hay–grass hay) was used as substrate in a batch culture ruminal incubation that included PT extracted from Ascophyllum nodosum, with and without polyethylene glycol. Principal ruminal bacteria were quantified using real‐time polymerase chain reaction. RESULTS: At 500 µg mL^?1, PT reduced growth of Fibrobacter succinogenes by 78%, 83% and 65% at 6, 12 and 24 h (P < 0.001), Ruminococcus albus at 24 h only (P < 0.01) and did not affect R. flavefaciens. Non‐cellulolytic bacteria Selenomonas ruminantium, Ruminobacter amylophilus and Prevotella bryantii were increased (P < 0.001) by PT at 12 and 24 h. Effects of PT on fermentation products (gas production, volatile fatty acid profiles and ammonia accumulation) were consistent with alterations in rumen microbial populations. CONCLUSION: The effects of PT on ruminal bacteria were species‐dependent, which suggests that diet may mediate PT effects on animal performance. The variation in sensitivity of ruminal bacteria to PT reflects previously reported effects of condensed tannins from terrestrial plants on microbial populations. Copyright © 2009 Crown in the right of Canada. Published by John Wiley & Sons, Ltd     

In vivo breakdown of dietary [methyl−14C] and [uronate-6−14C]pectin-labelled spinach cell walls by rat intestinal microorganisms and incorporation of 14C into host tissues

The metabolism of dietary plant cell wall (PCW) pectin was followed in the rat using PCW isolated from spinach cell cultures ¹⁴C-labelled in the galacturonic acid residues or pectic methyl ester groups. ¹⁴C-PCW were rapidly broken down in the caecum and colon of the rat and generated several groups of soluble products. [¹⁴C]Methanol was released from [methyl^?14C]pectin-labelled PCW and some of the methanol was converted to ¹⁴C-labelled volatile acids. ¹⁴C-Labelled volatile acids were also generated from [uronate-6-¹⁴C]pectin-labelled PCW along with soluble but non-volatile material. ¹⁴C derived from both cell wall types was taken up by the caecal and colonic mucosa and transported to the liver, pelt and other body tissues. Some ¹⁴C was excreted as ¹⁴CO₂ and in urine.     

Modulation of rumen pH by sodium bicarbonate and a blend of different sources of magnesium oxide in lactating dairy cows submitted to a concentrate challenge

With the objective of evaluating the potential effects of sodium bicarbonate or a magnesium-based product on rumen pH and milk performance of dairy cattle exposed to a dietary challenge, 30 lactating Holstein cows (648 ± 67 kg of body weight; 44.4 ± 9.9 kg/d of milk yield; 155 ± 75 d in milk) were blocked by parity (9 primiparous and 21 multiparous) and randomly distributed to 3 treatment groups. One group received a total mixed ration (TMR) that acted as a control (CTR), a second group (SB) received the same TMR but with an additional supplementation of 0.8% of sodium bicarbonate, and a third group (MG) received the same TMR as CTR but an additional supplementation of 0.4% of a magnesium-based product (pHix-Up, Timab, Dinard, France). After 1 wk of exposure to this TMR, all 3 rations were supplemented with 1 kg/d of barley, which was then increased 1 kg/wk until reaching 3 kg/d of barley during wk 4 of the study. Every kilogram of barley replaced 1 kg of forage in the diet. Individual feed intake and behavior were monitored using electronic feed bins. Seven cows per treatment were equipped with an intraruminal bolus that recorded pH every 15 min. As the severity of the barley challenge increased, dry matter intake decreased, but this decrease was more pronounced in SB cows than in MG cows, with an intermediate response for CTR cows. The MG cows produced more milk when challenged with 2 or 3 kg/d of additional barley than when challenged with 1 kg/d, whereas CTR cows produced less milk with the 3 kg/d challenge compared with 1 or 2 kg/d, and the SB cows maintained milk production. Milk fat content decreased with barley challenges, with CTR cows experiencing a more severe decrease than SB cows, which maintained stable butterfat values throughout the study, and MG cows showed a decline in milk fat content only with the 3 kg/d of additional barley. Meal size was also reduced as the severity of barley challenge increased, and this reduction was more modest in MG cows than in SB cows. The number of daily meals consumed by SB and MG cows was more constant than that recorded in CTR cows. Cows on the CTR and SB treatments showed a marked decrease in rumen pH with the 3 kg/d of additional barley, whereas MG cows maintained stable rumen pH during the barley challenges and had greater average rumen pH (5.93 ± 0.04) than CTR cows (5.83 ± 0.04) with the 3 kg/d of additional barley; SB cows showed intermediate values (5.85 ± 0.04). Last, MG cows spent less time (32.3 ± 6.1%) with rumen pH ≤5.8 when exposed to the 3 kg/d of barley challenge than CTR and SB cows (50.7 ± 5.02%). In conclusion, supplementation with MG prevents the decline in dry matter intake and milk production induced by a rumen challenge, whereas supplementation with SB prevents the decay in milk production but does not prevent the decrease in feed intake. These changes were probably due to the ability of the MG treatment to prevent a reduction in rumen pH when challenging cows with 3 kg/d of additional barley in the ration.