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C J Newbold

Publications and source records attributed to C J Newbold.

At least 37 records · Page 2Linked to original sources
PubMed1999

Effect of Yucca schidigera on ruminal fermentation and nutrient digestion in heifers.

In a replicated 3 x 3 Latin square experiment, six heifers (443 +/- 6.1 kg) fed a 61% barley grain:39% alfalfa silage diet (DM basis) were given intraruminal doses of powdered Yucca schidigera (YS). Doses of 0 (control), 20, or 60 g/d were given at 0800 daily. Ruminal content was sampled 0, 2, 4, and 6 h after dosing. Acidity, concentrations of reducing sugars, free amino acids, and peptides in the rumen were not affected (P > .05) by YS. Relative to control, ruminal ammonia concentration was reduced (P < .05) 2 h after YS dosing. Ruminal propionate concentration was increased (P < .05) by YS. Protozoal numbers in the rumen were lower (P < .05) with YS than without. Yucca did not affect (P > .05) rate or extent of in situ DM degradability. Fibrolytic, amylolytic, and proteolytic activities in ruminal contents were similar among treatments (P > .05). Dry matter intake, apparent digestibilities of DM, NDF, and CP, nitrogen balance, and microbial protein synthesis in the rumen were not affected (P > .05) by treatment. The effect of YS on ruminal ammonia concentration likely resulted from a decreased concentration of protozoa and, presumably, from ammonia binding by YS. The effect on ruminal propionate was probably a result of a selective inhibitory effect of YS on rumen microbial species.

Animals↗
PubMed1999

Influence of sodium fumarate addition on rumen fermentation in vitro.

The influence of sodium fumarate on rumen fermentation was investigated in vitro using batch and semi-continuous cultures of mixed rumen micro-organisms taken from three sheep receiving a basal diet of hay, barley, molasses, fish meal and a mineral-vitamin supplement (500, 299.5, 100, 91 and 9.5 g/kg DM respectively). Batch cultures consisted of 10 ml strained rumen fluid in 40 ml anaerobic buffer containing 200 mg of the same feed given to the sheep. Sodium fumarate was added to achieve a final concentration of 0, 5 or 10 mmol/l, as a result of the addition of 0, 250 or 500 mumol, equivalent to 0, 200 and 400 g/kg feed. CH4 production at 24 h (360 mumol in the control cultures) fell (P < 0.05) by 18 and 22 mumol respectively (SED 7.5). Total gas production was increased by the addition of fumarate without significant accumulation of H2. Substantial increases in acetate production (92 and 194 mumol; SED 26.7, P < 0.01) were accompanied by increases in propionate formation (212 and 396 mumol; SED 13.0, P < 0.001). Longer-term effects of fumarate supplementation on ruminal fermentation and CH4 production were investigated using the rumen simulation technique (Rusitec). Eight vessels were given 20 g basal diet/d, and half of them received a supplement of fumarate (disodium salt) over a period of 19 d. The response to the daily addition of 6.25 mmol sodium fumarate was a decrease in CH4 production of 1.2 mmol (SED 0.39, P < 0.05), equivalent to the consumption of 4.8 mmol H2, and an increase in propionate production of 4.9 mmol (from 10.4 to 15.3 (SED 1.05) mmol/d, P < 0.01). The inhibition of CH4 production did not decline during the period of time that fumarate was added to the vessels. Thus, the decrease in CH4 corresponded well to the fraction of the fumarate that was converted to propionate. Fumarate had no significant (P > 0.05) effect on total bacterial numbers or on the number of methanogenic archaea, but numbers of cellulolytic bacteria were increased (8.8 v. 23.9 (SED 2.49) x 10(5) per ml, P < 0.01). Fumarate also increased DM digestibility of the basal diet after 48 h incubation (0.476 v. 0.508 (SED 0.0123), P < 0.05). Thus, it was concluded that sodium fumarate may be a useful dietary additive for ruminants, because it diverts some H2 from CH4 production and because it is able to stimulate proliferation of cellulolytic bacteria and digestion of fibre.

Acetates↗
PubMed1999

Influence of peptides and amino acids on fermentation rate and de novo synthesis of amino acids by mixed micro-organisms from the sheep rumen.

The influence of different N sources on fermentation rate and de novo amino acid synthesis by rumen micro-organisms was investigated in vitro using rumen fluid taken from four sheep receiving a mixed diet comprising (g/kg DM): grass hay 500, barley 299.5, molasses 100, fish meal 91, minerals and vitamins 9.5. Pancreatic casein hydrolysate (P; comprising mainly peptides with some free amino acids; 10 g/l), free amino acids (AA; casein acid hydrolysate + added cysteine and tryptophan; 10 g/l), or a mixture of L-proline, glycine, L-valine and L-threonine (M; 0.83 g/l each) were added to diluted (1:3, v/v), strained rumen fluid along with 15NH4Cl (A; 1.33 g/l) and 6.7 g/l of a mixture of starch, cellobiose and xylose (1:1:1, by weight). P and AA, but not M, stimulated net gas production after 4 and 8 h incubation (P < 0.05) in comparison with A alone. P increased microbial-protein synthesis (P < 0.05) compared with the other treatments. All of the microbial-N formed after 10 h was synthesized de novo from 15NH3 in treatment A, and the addition of pre-formed amino acids decreased the proportion to 0.37, 0.55, and 0.86 for P, AA, and M respectively. De novo synthesis of amino acids (0.29, 0.42 and 0.69 respectively) was lower than cell-N. Enrichment of alanine, glutamate and aspartate was slightly higher than that of other amino acids, while enrichment in proline was much lower, such that 0.83-0.95 of all proline incorporated into particulate matter was derived from pre-formed proline. Glycine, methionine, lysine, valine and threonine tended to be less enriched than other amino acids. The form in which the amino acids were supplied, as P or AA, had little influence on the pattern of de novo synthesis. When the concentration of peptides was decreased, the proportion of microbial-N formed from NH3 increased, so that at an initial concentration of 1 g peptides/l, similar to the highest reported ruminal peptide concentrations, 0.68 of cell-N was formed from NH3. Decreasing the NH3 concentration at 1.0 g peptides/l caused proportionate decreases in the fraction of cell-N derived from NH3, from 0.81 at 0.53 g NH3-N/l to 0.40 at 0.19 g NH3-N/l. It was concluded that different individual amino acids are synthesized de novo to different extents by mixed rumen micro-organisms when pre-formed amino acids are present, and that the source of N used for synthesis of cell-N and amino acids depends on the respective concentrations of the different N sources available; however, supplementing only with amino acids whose synthesis is lowest when pre-formed amino acids are present does not stimulate fermentation or microbial growth.

Amino Acids↗
PubMed1998

Phylogenetic position and codon usage of two centrin genes from the rumen ciliate protozoan, Entodinium caudatum.

A lambda phage cDNA expression library was constructed from washed suspensions of the rumen ciliate protozoan, Entodinium caudatum, which had been maintained in an isolated, monofaunated sheep. The library was screened using an anti-E. caudatum antiserum raised in rabbits against sonically disrupted protozoa, DNA sequences for two centrins or caltractins, a subfamily of the EF-hand Ca(2+)-modulated proteins which are closely related, highly conserved cytoskeletal proteins, were identified and characterised. Their phylogenetic position was established relative to other centrin gene sequences. The two proteins showed homology to Paramecium tetraurelia centrins: 50 and 52% identities and 71 and 75% similarities in the protein sequence, over 99 and 110 amino acids fragments. Codon usage and indices revealed the E. caudatum follows universal codon usage, but with a restricted number of codons, and has a low G&C content.

Animals↗
PubMed1998

Uptake of acetylated peptides from the small intestine in sheep and their nutritive value in rats.

Acetylation is a potential method for protecting dietary peptides from degradation by rumen micro-organisms. As a first step in determining the nutritive value of acetylated peptides, their disappearance in the small intestine of sheep and their ability to support growth in a rat bioassay were measured. 15N-labelled peptides were prepared from lucerne which had been grown with 15N-labelled (NH4)2SO4 in the absence of Rhizobium. Peptides were prepared by enzymic hydrolysis of the extracted protein. Two peptide preparations were made using different proteinase mixtures. These mixtures contained peptides with an average molecular weight of 559 and 522 Da. They were treated with acetic anhydride, which resulted in 85 and 88% modification respectively, and their uptake from the small intestine was determined by injecting 1 g of untreated or acetylated peptides in a Cr-EDTA solution into the jejunum of two sheep fitted with jejunal catheters and ileal cannulas. Ileal digesta were collected and analysed for Cr and 15N. The uptake of dialanine (Ala2) and N-acetyl-Ala2 were compared in a similar way. The disappearance of 15N from lucerne peptides was high (88 and 93% respectively) and this was not affected significantly by acetylation (86 and 87%). Corresponding values for Ala2 and N-acetyl-Ala2 were both 96%, as measured by HPLC. It was therefore concluded that acetylation did not affect the uptake of peptides from the small intestine in sheep. Two feeding trials were carried out with rats. The first trial was carried out with a protein-free diet to which was added 10% lactalbumin or 5% lactalbumin and then a mixture of methionine-free amino acids, either alone or supplemented with Met, Gly-Met or acetylated Gly-Met. The rats grew equally well on all sources of Met, but failed to grow significantly on the mixture of Met-free amino acids. In the second trial the diet contained casein as 5.9% of the basal diet. Additional casein, pancreatic casein hydrolysate (peptides) and acetylated pancreatic casein hydrolysate (acetylated peptides) were compared as sources of amino acids, at inclusion rates of 100 g/kg final diet. Feed intake was similar with casein and peptides treatments, but was depressed by 23% with acetylated peptides. Live weight gain was 15 and 75% lower with the peptides and acetylated peptides diets respectively. Addition of lysine, arginine or histidine did not restore feed intake or weight gain of rats receiving acetylated peptides, but feed intake was restored immediately when peptides replaced acetylated peptides. When intake was restricted to 9 g/d and acetylated casein hydrolysate replaced half of the protein in the diet, rats gained weight less rapidly (1.44 v. 1.09 g/d) and retained less N, such that only 0.36 of the acetylated peptide-N was calculated to remain available to the animal. This N retention compared with 0.70 for unmodified casein. Thus, the rat bioassay indicated that certain specific peptides may well be of high nutritive value following acetylation, but that there may be problems of inappetance and inefficient utilization with acetylated peptide mixtures.

Acetylation↗
PubMed1998

Influence of dietary acetylated peptides on fermentation and peptidase activities in the sheep rumen.

The predominant mechanism of peptide breakdown by rumen micro-organisms is aminopeptidase. Thus acetylation of the N-terminus of peptides inhibits their degradation by rumen micro-organisms in short-term incubations with rumen fluid in vitro. An experiment was undertaken to determine if adaptation of the rumen microbial population would take place when acetylated peptides were fed for a prolonged period, which would enable the microbial population to break down the protected peptides and thus decrease their nutritive value. Three adult sheep, fitted with permanent rumen cannulae, received a maintenance hay/concentrate diet to which was added, at each meal, 20 g of casein enzymic hydrolysate ('peptides') or 20 g of peptides previously treated with acetic anhydride. The diets were fed for 28 d in a 3 x 3 latin square and samples were taken during the last 7 d. Fermentation products and NH3 concentrations indicated that acetylated peptides remained less degradable than untreated peptides. There was a trend towards increased proteolytic activity with acetylated peptides, and dipeptidase activity increased by 18% and 28%, respectively, compared with untreated peptides and control treatments. Activity against N-acetyl-Ala2 also increased when acetylated peptides were fed, but it remained only 13% of the rate of Ala2 hydrolysis. No increase was found in the rate of ammonia production from acetylated peptides in animals receiving acetylated peptides--this rate was 26% of that found with untreated peptides--and acetylated peptides continued to persist for longer in the rumen than untreated peptides after feeding. Thus it was concluded that the rumen microbial population did not adapt to utilize acetylated peptides.

Acetylation↗
PubMed1998

Estimation of the relative abundance of different Bacteroides and Prevotella ribotypes in gut samples by restriction enzyme profiling of PCR-amplified 16S rRNA gene sequences.

We describe an approach for determining the genetic composition of Bacteroides and Prevotella populations in gut contents based on selective amplification of 16S rRNA gene sequences (rDNA) followed by cleavage of the amplified material with restriction enzymes. The relative contributions of different ribotypes to total Bacteroides and Prevotella 16S rDNA are estimated after end labelling of one of the PCR primers, and the contribution of Bacteroides and Prevotella sequences to total eubacterial 16S rDNA is estimated by measuring the binding of oligonucleotide probes to amplified DNA. Bacteroides and Prevotella 16S rDNA accounted for between 12 and 62% of total eubacterial 16S rDNA in samples of ruminal contents from six sheep and a cow. Ribotypes 4, 5, 6, and 7, which include most cultivated rumen Prevotella strains, together accounted for between 20 and 86% of the total amplified Bacteroides and Prevotella rDNA in these samples. The most abundant Bacteroides or Prevotella ribotype in four animals, however, was ribotype 8, for which there is only one known cultured isolate, while ribotypes 1 and 2, which include many colonic Bacteroides spp., were the most abundant in two animals. This indicates that some abundant Bacteroides and Prevotella groups in the rumen are underrepresented among cultured rumen Prevotella isolates. The approach described here provides a rapid, convenient, and widely applicable method for comparing the genotypic composition of bacterial populations in gut samples.

Animals↗
PubMed1998

De novo synthesis of amino acids by the ruminal bacteria Prevotella bryantii B14, Selenomonas ruminantium HD4, and Streptococcus bovis ES1.

The influence of peptides and amino acids on ammonia assimilation and de novo synthesis of amino acids by three predominant noncellulolytic species of ruminal bacteria, Prevotella bryantii B14, Selenomonas ruminantium HD4, and Streptococcus bovis ES1, was determined by growing these bacteria in media containing 15NH4Cl and various additions of pancreatic hydrolysates of casein (peptides) or amino acids. The proportion of cell N and amino acids formed de novo decreased as the concentration of peptides increased. At high concentrations of peptides (10 and 30 g/liter), the incorporation of ammonia accounted for less than 0.16 of bacterial amino acid N and less than 0.30 of total N. At 1 g/liter, which is more similar to peptide concentrations found in the rumen, 0.68, 0.87, and 0.46 of bacterial amino acid N and 0.83, 0.89, and 0.64 of total N were derived from ammonia by P. bryantii, S. ruminantium, and S. bovis, respectively. Concentration-dependent responses were also obtained with amino acids. No individual amino acid was exhausted in any incubation medium. For cultures of P. bryantii, peptides were incorporated and stimulated growth more effectively than amino acids, while cultures of the other species showed no preference for peptides or amino acids. Apparent growth yields increased by between 8 and 57%, depending on the species, when 1 g of peptides or amino acids per liter was added to the medium. Proline synthesis was greatly decreased when peptides or amino acids were added to the medium, while glutamate and aspartate were enriched to a greater extent than other amino acids under all conditions. Thus, the proportion of bacterial protein formed de novo in noncellulolytic ruminal bacteria varies according to species and the form and identity of the amino acid and in a concentration-dependent manner.

Amino Acids↗
PubMed1997

Peptidases of the rumen bacterium, Prevotella ruminicola.

Prevotella (formerly Bacteroides) ruminicola is a numerous rumen bacterium which plays a significant role in the metabolism of proteins and peptides in the rumen. Measurement of the hydrolysis of synthetic aminopeptidase substrates by sonicated extracts and whole cells of different species of rumen bacteria indicated that P. ruminicola had the greatest range and specific activity of dipeptidyl peptidases among the species tested. Streptococcus bovis hydrolysed some dipeptidyl peptidase substrates to a lesser extent, and several species broke down Ala2-p-nitroanilide, including Ruminobacter amylophilus, Ruminococcus spp. and Veillonella parvula. Dipeptidyl peptidases, which cleave dipeptides from the amino-terminus of longer peptides, were much more active than aminopeptidases removing single amino acids in P. ruminicola. Ion-exchange chromatography of sonicated extracts of P. ruminicola M384 revealed at least four distinct activities: one hydrolysed Ala2-p-nitroanilide, ValAla-p-nitroanilide, Ala4and Ala5; another was an O2-sensitive activity hydrolysing GlyArg-4-methoxynapthylamide, ArgArg-4-methoxynaphthylamide, Gly5 and ValGlySerGlu, similar to dipeptidyl peptidase type I DPP-1); a third hydrolysed GlyPro-p-nitroanilide and GlyPro-4-methoxynapthylamide and was similar to dipeptidyl peptidase type IV XDPP-4); a fourth broke down LysAla-4-methoxynaphthylamide. All of the enzymes, and particularly those active against Ala2-p-nitroanilide and GlyPro-p-nitroanilide, were inhibited by serine protease inhibitors, and all except DPP-4 were inhibited by EDTA. Both DPP-1 and the enzyme hydrolysing LysAla-4-methoxynaphthylamide were inhibited strongly by iodoacetate. DPP-4 was inhibited completely by diprotin A. Competitive inhibition experiments suggested that DPP-1 was less important than the other enzymes in the breakdown of peptide mixtures.

Journal Article↗
PubMed1997

Influence of foliage from African multipurpose trees on activity of rumen protozoa and bacteria.

Samples and extracts of foliage from African multipurpose trees were screened for their effects on rumen protozoa and bacteria with a view to predicting their safety as feed supplements and for identifying species with potential antiprotozoal activity. The species tested were Acacia aneura, Chamaecytisus palmensis, Brachychiton populneum, Flindersia maculosa, Sesbania sesban, Leucaena leucocephala and Vernonia amyedalina. Antimicrobial effects were mild except for S. sesban, which was highly toxic to rumen protozoa in vitro, and A. aneura, which was toxic to rumen bacteria. The antiprotozoal factor in S. sesban was apparently associated with the fraction of the plant containing saponins. When S. sesban was fed to sheep, protozoal numbers fell by 60% after 4 d, but the population recovered after a further 10 d. In vitro experiments demonstrated that washed protozoa from later times were no more resistant to S. sesban than on initial exposure, suggesting that other micro-organisms, probably the bacteria, adapted to detoxify the antiprotozoal agent. Thus S. sesban may be useful in suppressing protozoa and thereby improving protein flow from the rumen, but only if the bacterial metabolism of the antiprotozoal factor can be avoided.

Africa↗
PubMed1996

Mode of action of the yeast Saccharomyces cerevisiae as a feed additive for ruminants.

Two suggested modes of action of yeast in stimulating rumen fermentation were investigated. The first, that yeast respiratory activity protects anaerobic rumen bacteria from damage by O2, was tested using different strains of yeast that had previously been shown to have differing abilities to increase the viable count of rumen bacteria. Saccharomyces cerevisiae NCYC 240, NCYC 1026, and the commercial product Yea-Sacc, added to rumen fluid in vitro at 1.3 mg/ml, increased the rate of O2 disappearance by between 46 and 89%. The same three preparations also stimulated bacterial numbers in an in vitro fermenter (Rusitec). S. cerevisiae NCYC 694 and NCYC 1088, which had no influence on the viable count in Rusitec, also had no effect on O2 uptake. Respiration-deficient (RD) mutants of S. cerevisiae NCYC 240 and NCYC 1026 were enriched by repeated culturing in the presence of ethidium bromide. S. cerevisiae NCYC 240 and NCYC 1026 stimulated the total and cellulolytic bacterial populations in Rusitec, while the corresponding RD mutants did not. Rigorous precautions to exclude air from Rusitec resulted in S. cerevisiae NCYC 240 no longer stimulating total bacterial numbers, although it still increased numbers of cellulolytic bacteria. The second hypothesis, that yeast provides malic and other dicarboxylic acids which stimulate the growth of some rumen bacteria, was examined by comparing the effects of yeast and malic acid on rumen fermentation in sheep. Three mature sheep were given 0.85 kg barley/d plus 0.55 kg chopped ryegrass hay/d either unsupplemented, or supplemented with 4 g S. cerevisiae NCYC 240/d or 100 mg L-malic acid/d either mixed with the diet or in aqueous solution infused continuously into the rumen. Yeast increased the total viable count of bacteria (P < 0.05) whereas malic acid did not, and no other effect of the treatments reached statistical significance. It was concluded, therefore, that the stimulation of rumen bacteria by S. cerevisiae is at least partly dependent on its respiratory activity, and is not mediated by malic acid.

Animals↗
PubMed1996

Inhibition by 1,10-phenanthroline of the breakdown of peptides by rumen bacteria and protozoa.

The rate of peptide breakdown in the rumen frequently exceeds the rate at which the amino acids released can be used for microbial growth. The final step in this often wasteful process involves the cleavage of dipeptides. The main rumen bacterial species with high dipeptidase activity, Prevotella ruminicola, Fibrobacter succinogenes, Lachnospira multipara and Megasphaera elsdenii, had activities which were inhibited > 95% by 1,10-phenanthroline, a chelator of divalent metal ions and metalloprotease inhibitor. Dipeptidase activity in digesta taken from the rumen of sheep decreased by 33% in the presence of 1,10-phenanthroline, while mixed bacteria from the same samples were inhibited by 80% and the activity of mixed protozoa decreased by only 15%. Thus a substantial amount of dipeptide breakdown appears to be due to ciliate protozoa in the mixed population. Extensive washing of the protozoa increased the sensitivity of protozoal dipeptidase activity to 1,10-phenanthroline, suggesting that protozoa too have a metallo-dipeptidase activity but that it is normally protected from inhibition by 1,10-phenanthroline. Breakdown of the pentapeptide, Ala5, was also inhibited 27% by 1,10-phenanthroline in the mixed population, and when Trypticase, a pancreatic casein hydrolysate containing a mixture of oligopeptides, dipeptides and amino acids, was incubated with rumen fluid, the production of ammonia and free amino groups was inhibited 71% by 1,10-phenanthroline. It was concluded that metal ion chelation inhibits oligopeptidase and dipeptidase activities of rumen micro-organisms and may be a means of controlling ammonia production from peptides in the rumen.

Ammonia↗
PubMed1996

The role of ciliate protozoa in the lysis of methanogenic archaea in rumen fluid.

Predation by ciliate protozoa can account for 90% of the eubacterial protein turnover in the rumen. However, little is known about the factors affecting the lysis of archaea in rumen fluid. Bacterial lysis was followed from the release of acid-soluble 14C from 14C leucine-labelled bacteria. The rumen methanogen Methanobrevibacter MF1 was broken down more rapidly than other non-ruminal archaea in rumen fluid withdrawn from sheep harbouring either a mixed protozoa population or monofaunated with Polyplastron multivesiculatum or Entodinium spp. The removal of protozoa from the rumen fluid had little effect on the breakdown of Methanobrevibacter, while lysis of the non-methanogenic ruminal bacterium Selenomonas ruminantium decreased by over 70%. Substantial lysis of Methanobrevibacter occurred in cell-free rumen fluid and this effect could be abolished by autoclaving. In view of the high number of bacteriophages in rumen fluid and susceptibility of ruminal bacteria to phage-induced lysis it is tempting to suggest that phages have a role in the lysis of archaea in rumen fluid.

Animals↗
PubMed1995

Cleavage of di- and tripeptides by Prevotella ruminicola.

The final step in the conversion of protein to amino acids by the common Gram-negative rumen bacterium, Prevotella (formerly Bacteroides) ruminicola , is the cleavage of di- and tripeptides. Dipeptidase and tripeptidase activities were predominantly cytoplasmic, and toluene treatment increased the rate of Ala2 and Ala3 hydrolysis by whole cells, suggesting that transport limited the rate of hydrolysis of extracellular di- and tripeptides. The hydrolysis of Ala2 and Ala3 by whole cells was not affected by protonophores, ionophores or dicyclohexylcarbodiimide, but Ala2 hydrolysis by EDTA-treated cells was inhibited by the Ca2+/H+ ionophore, tetronasin. Ala3 hydrolysis was not affected by protonophores or ionophores in EDTA-treated cells. The dipeptidase of strain M384 was inhibited > 99% by 1,10-phenanthroline and 39% by EDTA but not other protease inhibitors, consistent with the enzyme being a metalloprotease. Tripeptidase was insensitive to protease inhibitors, except for a 33% inhibition by EDTA. Cleavage of tripeptides occurred at the bond adjacent to the N-terminal amino acid. Distinct di-, tri- and oligopeptidase peaks were obtained by anion-exchange liquid chromatography of disrupted cells. Banding patterns on native PAGE using activity staining also indicated that P. ruminicola M384 had separate single dipeptidase and tripeptidase enzymes which hydrolysed a range of peptides. The dipeptidase of strain M384 was different from other strains of P. ruminicola: strains GA33 and B(1)4 had activities which ran at the same R(f); strain GA33 had another band of lower activity; strain 23 had two bands different from those of the other strains. The tripeptidases ran at the same R(f) for the different strains. Dipeptidase activity of all strains was inhibited by 1,10-phenanthroline on gels. Gel permeation chromatography indicated that the M(r) of the dipeptidases from strains M384 and B(1)4 were 115,000 and 114,500 respectively, and 112,500 and 121,500 for the corresponding tripeptidases. Thus the metabolism of small peptides by P. ruminicola involves separate permeases and intracellular peptidases for di- and tripeptides.

Journal Article↗
PubMed1995

Interactions between rumen anaerobic fungi and ciliate protozoa in the degradation of rice straw cell walls.

Suspensions of mixed rumen protozoa were added to incubations of the anaerobic fungus Neocallimastix patriciarum with rice straw cell walls. The protozoa did not influence the dry matter lost from the straw, or the solubilization of monosaccharides, but they had a marked effect on the fermentation products formed. Studies with 14C-labelled protozoa suggested that the presence of protozoa reduced the fungal carboxymethylcellulase activity to around half of that found in pure cultures of the fungus.

Anaerobiosis↗
PubMed1995

The importance of methanogens associated with ciliate protozoa in ruminal methane production in vitro.

The importance of methanogenic bacteria associated with ciliate protozoa was estimated either by removing protozoa from whole rumen fluid (using defaunated rumen fluid to correct for the effects of centrifugation on bacteria) or by isolating the protozoa. Rumen fluid was withdrawn from sheep inoculated with either Polyplastron multivesiculatum, a co-culture of Isotricha prostoma plus Entodinium spp. or a mixed type B fauna of Entodinium, Eudiplodinium and Epidinium spp. Methanogenesis was highest in rumen fluid containing a mixed protozoal population of the following genera: Entodinium, Eudiplodinium and Epidinium, was lower in defaunated rumen fluid and lowest in rumen fluid containing either I. prostoma plus Entodinium or P. multivesiculatum. Methanogenic bacteria associated with rumen ciliates were apparently responsible for between 9 and 25% of methanogenesis in rumen fluid.

Animals↗
PubMed1995

Different strains of Saccharomyces cerevisiae differ in their effects on ruminal bacterial numbers in vitro and in sheep.

A ruminal simulation device (Rusitec) was used to compare the effects of Saccharomyces cerevisiae strains NCYC 240, NCYC 694, NCYC 1026, NCYC 1088, and Yea-Sacc (a commercial product containing S. cerevisiae) on ruminal fermentation. S. cerevisiae NCYC 240, NCYC 1088, NCYC 1026, and NCYC 694 were grown on malt extract at 30 degrees C in aerated fed-batch culture and harvested along with spent growth medium by freeze-drying. Each vessel received daily 20 g of a basal diet consisting of hay, barley, molasses, fishmeal, and a minerals/vitamins mixture at 500, 299.5, 100, 91, and 9.5 g/kg of DM, respectively. Yeast preparations (500 mg/d) were added along with the feed. S. cerevisiae NCYC 240, NCYC 1026, and Yea-Sacc stimulated total and cellulolytic bacterial numbers, whereas S. cerevisiae NCYC 694 and NCYC 1088 had no effect on the numbers of bacteria. The effects of S. cerevisiae NCYC 240, NCYC 1026, and Yea-Sacc on ruminal fermentation were further investigated in vivo using ruminally cannulated sheep fed 1.5 kg/d of the diet used in Rusitec, supplemented with 2 g/d of yeast culture. All treatments tended to stimulate total and cellulolytic bacterial numbers. However, the stimulation was only statistically significant for S. cerevisiae NCYC 1026 with total bacterial numbers and S. cerevisiae NCYC 240 with cellulolytic bacteria (P < .05). Increased bacterial numbers were associated with an increase in the rate of straw degradation in the rumen and a nonsignificant (P > .05) increase in the excretion of purine derivatives in the urine, measured as an index of microbial nitrogen leaving the rumen.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗