Effect of soluble carbohydrates on digestion of cellulose by pure cultures of rumen bacteria.

The rate of cellulose digestion in the presence of either glucose or cellobiose was studied for the three predominant species of cellulolytic rumen bacteria: Ruminococcus albus, Ruminococcus flavefaciens, and Bacteroides succinogenes. When a soluble carbohydrate was added to cellulose broth, the lag phase of cellulose digestion was shortened. Presumably, this was due to greater numbers of bacteria, because increasing the size of the inoculum had a similar effect. Cellulose digestion occurred simultaneously with utilization of the soluble carbohydrate. The rate of cellulose digestion slowed markedly for B. succinogenes and R. flavefaciens and slowed less for R. albus after the cellobiose or glucose had been utilized, and was accompanied by a decrease in pH. Both the rate and the extent of cellulose digestion were partially inhibited when the initial pH of the medium was 6.3 or below. R. albus appeared to be less affected by a low-pH medium than were B. succinogenes and R. flavefaciens. When a soluble carbohydrate was added to the fermentation during the maximum-rate phase of cellulose digestion, the rate of cellulose digestion was not affected until after the soluble carbohydrate had been depleted and the pH had decreased markedly. Prolonged exposure of the bacteria to a low pH had little if any effect on their subsequent ability to digest cellulose. Cellulase activity of intact bacterial cells appeared to be constitutive in nature for these three species of rumen bacteria.     

Effect of soluble carbohydrates on digestion of cellulose by pure cultures of rumen bacteria

The rate of cellulose digestion in the presence of either glucose or cellobiose was studied for the three predominant species of cellulolytic rumen bacteria: Ruminococcus albus, Ruminococcus flavefaciens, and Bacteroides succinogenes. When a soluble carbohydrate was added to cellulose broth, the lag phase of cellulose digestion was shortened. Presumably, this was due to greater numbers of bacteria, because increasing the size of the inoculum had a similar effect. Cellulose digestion occurred simultaneously with utilization of the soluble carbohydrate. The rate of cellulose digestion slowed markedly for B. succinogenes and R. flavefaciens and slowed less for R. albus after the cellobiose or glucose had been utilized, and was accompanied by a decrease in pH. Both the rate and the extent of cellulose digestion were partially inhibited when the initial pH of the medium was 6.3 or below. R. albus appeared to be less affected by a low-pH medium than were B. succinogenes and R. flavefaciens. When a soluble carbohydrate was added to the fermentation during the maximum-rate phase of cellulose digestion, the rate of cellulose digestion was not affected until after the soluble carbohydrate had been depleted and the pH had decreased markedly. Prolonged exposure of the bacteria to a low pH had little if any effect on their subsequent ability to digest cellulose. Cellulase activity of intact bacterial cells appeared to be constitutive in nature for these three species of rumen bacteria.     

Assessment of ciliates in the sheep rumen by DGGE

AIMS: This work was carried out to develop a rapid molecular profiling technique to screen ciliate populations in the rumen of sheep. METHODS AND RESULTS: DGGE was used to study the ciliate diversity in the rumen of sheep. There was considerable variation between sheep which were co-housed, and fed the same diet. However, no difference in the major banding patterns was detected, when samples were collected from a single sheep sampled at different points. Following dietary changes, use of a pair-wise comparison of lanes, demonstrated that although there was still diversity between the ciliate population of sheep, the effects as a result of dietary changes were greater. CONCLUSIONS: The technique generated molecular profiles which are sufficiently different to allow comparison between samples, and to permit molecular ecological studies on the rumen ciliate population. SIGNIFICANCE AND IMPACT OF THE STUDY: The outcome of this study means that ciliate diversity in the rumen may now be studied by those unfamiliar with morphological identification of these organisms.     

Almost pure I(alpha) cellulose in the cell wall of Glaucocystis.

Crystalline features of cellulose microfibrils in the cell walls of Glaucocystis (Glaucophyta) were studied by combined spectroscopy and diffraction techniques, and the results were compared with those of Oocystis (Chlorophyta). Although these algae are grouped into two different classes, by the composition of their chloroplasts for instance, their cell walls are quite similar in size and morphology. The most striking features of their cellulose crystallites are that they have the highest cellulose I(alpha) contents reported to date. In particular, the I(alpha) fraction of cellulose from Glaucocystis was found to be as high as 90% from (13)C NMR analysis. The mode of preferential orientation of cellulose crystallites in their cell walls is also interesting; equatorial 0.53-nm lattice planes were oriented parallel to the cell surface in the case of Glaucocystis, while the 0.62-nm planes were parallel to the Oocystis cell surface. Such a structural variation provides another link to the evolution of cellulose structure, biosynthesis, and its biocrystallization mechanism.     

Effect of the rumen ciliates Entodinium caudatum, Epidinium ecaudatum and Eudiplodinium maggii, and combinations thereof, on ruminal fermentation and total tract digestion in sheep

The quantitative importance of individual ciliate species and their interaction in the rumen is still unclear. The present study was performed to test whether there are species differences in the influence on ruminal fermentation in vivo and if combinations of ciliates act additive in that respect. Six adult wethers fed a hay-concentrate diet were defaunated, then refaunated either with Entodinium caudatum (EC), Epidinium ecaudatum (EE) or Eudiplodinium maggii (EM) alone, then progressively with all possible species combinations. Feed, faeces, urine, ruminal fluid and gas were sampled for eight days always after at least 21 days of adaptation. With a linear mixed model, accounting for the 2 x 2 x 2 full factorial study design, mean marginal effect sizes, i.e., the magnitude of change in variables as caused by the presence of each ciliate species or of combinations of them, were estimated. The apparent digestibility of organic matter and neutral detergent fibre remained unaffected. The apparent N digestibility increased by 0.054 with EM (0.716 with defaunation). Ruminal ammonia increased by 1.6, 4.0 and 8.7 mmol/l in the presence of EM, EC and EE, respectively, compared to defaunation (6.9 mmol/l). In the EM + EE combination, ruminal ammonia was lower than would have been expected from an additive effect. With EE, total short-chain fatty acids increased by 23 mmol/l (100 mmol/l with defaunation), but not when EE was combined with EM. The acetate-to-propionate ratio decreased by 0.73 units in the presence of EE (4.0 with defaunation), but only when EE was the sole ciliate species in the rumen. In the presence of any ciliate species, the 16S rDNA copies of total Bacteria and major fibrolytic species decreased to 0.52- and 0.22-fold values, respectively of that found without protozoa. Total Archaea were unaffected; however, Methanobacteriales copies increased 1.44-fold with EC. The CH4-to-CO2 ratio of ruminal gas decreased by 0.036 with EM and 0.051 with EE (0.454 with defaunation). In conclusion, individual ciliates affected ruminal fermentation differently and, when different species were combined, sometimes in a non-additive manner. From the ciliates investigated, EE affected ruminal fermentation most and might play a dominant role in mixed ciliate populations.     

Effect of the rumen ciliates Entodinium caudatum,Epidinium ecaudatum and Eudiplodinium maggii,and combinations thereof,on ruminal fermentation and total tract digestion in sheep

The quantitative importance of individual ciliate species and their interaction in the rumen is still unclear. The present study was performed to test whether there are species differences in the influence on ruminal fermentation in vivo and if combinations of ciliates act additive in that respect. Six adult wethers fed a hay-concentrate diet were defaunated, then refaunated either with Entodinium caudatum (EC), Epidinium ecaudatum (EE) or Eudiplodinium maggii (EM) alone, then progressively with all possible species combinations. Feed, faeces, urine, ruminal fluid and gas were sampled for eight days always after at least 21 days of adaptation. With a linear mixed model, accounting for the 2 × 2 × 2 full factorial study design, mean marginal effect sizes, i.e., the magnitude of change in variables as caused by the presence of each ciliate species or of combinations of them, were estimated. The apparent digestibility of organic matter and neutral detergent fibre remained unaffected. The apparent N digestibility increased by 0.054 with EM (0.716 with defaunation). Ruminal ammonia increased by 1.6, 4.0 and 8.7 mmol/l in the presence of EM, EC and EE, respectively, compared to defaunation (6.9 mmol/l). In the EM + EE combination, ruminal ammonia was lower than would have been expected from an additive effect. With EE, total short-chain fatty acids increased by 23 mmol/l (100 mmol/l with defaunation), but not when EE was combined with EM. The acetate-to-propionate ratio decreased by 0.73 units in the presence of EE (4.0 with defaunation), but only when EE was the sole ciliate species in the rumen. In the presence of any ciliate species, the 16S rDNA copies of total Bacteria and major fibrolytic species decreased to 0.52- and 0.22-fold values, respectively of that found without protozoa. Total Archaea were unaffected; however, Methanobacteriales copies increased 1.44-fold with EC. The CH₄-to-CO₂ ratio of ruminal gas decreased by 0.036 with EM and 0.051 with EE (0.454 with defaunation). In conclusion, individual ciliates affected ruminal fermentation differently and, when different species were combined, sometimes in a non-additive manner. From the ciliates investigated, EE affected ruminal fermentation most and might play a dominant role in mixed ciliate populations.     

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

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

28种禾本科植物种子形态学特征及其萌发对绵羊瘤胃消化的反应

采用瘘管羊瘤胃瘘管尼龙袋法,对北疆地区常见的28种禾本科植物种子进行不同时间段的瘤胃消化处理,对处理前后种子的长、宽、厚、形状指数、百粒重和萌发率进行了测量,研究种子对绵羊瘤胃消化的反应,以期丰富北疆地区植物种子消化道传播的内容.结果表明: 除臭草、剪股颖、鳞茎早熟禾、猫尾草和小麦以外,其余23种植物的种子均为椭圆或扁平状种子;小麦和燕麦种子百粒重分别为3.52和1.69 g,其余种子的百粒重均为0.01～1 g,属中等或偏小类型.种子经瘤胃消化后,颜色变深,种子结构被破坏,种子的芒、稃和颖等附属结构的长度随消化时间的延长逐渐减小;种子长、宽、厚、百粒重随消化时间的延长呈逐渐减小趋势,但变化不显著;种子经绵羊瘤胃消化后,萌发率显著降低,经瘤胃消化6 h后,除鹅观草和燕麦种子萌发率降为0外,其余26种植物仍有部分种子保持活力.     

Effect of different protein sources on the concentrations of small peptides in the rumen of sheep

The experiment was conducted to determine the effect of different protein sources on concentration of small peptides (Pro-Ala, Val-Val, Pro-Leu, Met-Met) in the rumen fluid of sheep. Four Inner Mongolia Sunite sheep fitted with permanent cannulas were used in a 4 x 4 Latin square design, and fed four different protein sources including soybean meal (SBM), casein (Casein), fish meal (FM) and corn gluten meal (CGM), respectively. The results showed that the concentration of Pro-Ala peaked in Casein, FM, CGM groups at 2 h after feeding, whereas the highest level was measured at 6 h after feeding in SBM group. Val-Val and Pro-Leu production were highest at 6 h after feeding Casein and CGM diets and 4 h after feeding SBM and FM diets, respectively. During 6 h after feeding the accumulative concentration of Pro-Ala (1.74 mg/l) and Pro-Leu (25.78 mg/l) in rumen was highest for the Casein diet. During the total sampling time, the highest amount of accumulated small peptides was measured for Pro-Leu, and lowest amount for Met-Met, which was independent of treatment groups. Experimental results proved that small peptides with N-terminal Pro and a hydrophobic structure could inhibit rumen degradation and may be available for post-ruminal absorption.     

Effect of feeding tree leaves as supplements on the nutrient digestion and rumen fermentation pattern in sheep grazing on semi-arid range of India – I

A study was carried out to determine the effect of feeding different tree leaves as supplements on nutrient digestion, rumen fermentation and blood parameters of sheep grazing on a semi-arid rangeland. Thirty adult Malpura rams of uniform body weight (39.0 ± 0.75) were divided into five groups of six each. They were grazed as a single flock from 08.00 to 17.00 h on a semi-arid rangeland. After the end of the grazing period, the first group (G1), which was not provided with any supplementation, served as the control. The second group (G2) was supplemented with 200 g of a concentrate mixture per head per day, whereas the third, fourth and fifth groups (G3–G5) were provided with approximately 200 g DM d⁻¹ of freshly cut foliage from Prosopis cineraria, Acacia nilotica and Albezia lebbek. The foliage from P. cineraria contained 133.4 g kg⁻¹ DM condensed tannin (CT) with protein precipitating capacity (PPC) of 66 g kg⁻¹ DM, whereas A. nilotica contained 18.9 g kg⁻¹ DM hydrolysable tannin (HT) with PPC of 11.5 g kg⁻¹ DM. However, A. lebbek did not contain any tannin. The protein contents were 119, 139 and 194 g kg⁻¹ DM, respectively. The DMI (g d⁻¹) was 688, 916, 1024, 1003, 999 in G1, G2, G3, G4 and G5, respectively. Digestible crude protein (DCP) and metabolizable energy (ME) intakes in supplemented groups G2–G5 were higher (P < 0.05) than in the control (G1). Supplementation improved the DM digestibility in all groups, whereas CP digestibility was lower (P < 0.05) in G3 compared to G2, G4 and G5. Rumen fermentation study conducted 6 h after supplementation revealed that total N, ammonia N, and total VFA levels were lower (P < 0.05) in G3 compared to the other supplemented groups. Although the haemoglobin (Hb) levels were similar among groups, blood urea N (BUN) was lowest in G3 compared to the other groups. The initial body weights were similar among groups (mean 39 kg). After 60 days of experimental feeding, all groups maintained their body weight, except the control group (G1), which lost body weight. It was observed, that supplementation with tree leaves containing CT like P. cineraria helps in better rumen fermentation pattern by preventing excessive loss of nitrogen. It was concluded that maximum nutritional benefits of tree leaves could be harvested, if used as supplement rather than as a sole feed.     

Structure of rigid-layer of Rhizobium cell wall. I. Purification on the peptidoglycan from the cellulose microfibrils

The bag shaped peptidoglycan layer of Rhizobium cell wall was isolated from intact cells after treatment with sodium dodecylsulfate and trypsin, chymotrypsin or pepsin digestion. Results of chemical analysis of acid hydrolyzed peptidoglycan revealed beside two amino sugars: glucosamine and muramic acid, three major amino acids; alanine, glutamic acid and 2,6-diaminopimelic acid and also significant amount of glucose. Evidence were provided that the polyglucose found in peptidoglycan preparations of three strains of Rhizobium trifolii, one of Rhizobium leguminosarum and one of Rhizobium meliloti consist of cellulose microfibrils. The content of cellulose present in Rhizobium peptidoglycans ranged from 60 to 80%. Methods of peptidoglycan purification from the cellulose microfibrils are described.     

In situ starch degradation of different feeds in the rumen

The in situ starch degradation of 5 feeds (barley, maize, pea, oats and wheat bran) has been measured (trial 1), and the influence of particle size on starch degradation investigated with 3 feeds (barley, maize, pea) (trial 2). The starch degradability of barley, oats and wheat bran was found to be higher than that of pea, and higher again than that of maize: 98, 97, 96, 90 and 58% respectively. For barley, oats and wheat bran, starch was degraded more rapidly than the other dry matter (pm) components. Maize and pea starches were degraded at the same rate as non-starchy components. The particle size variations between feeds ground on the same screen may partly explain variations in starch degradability. When the particle size increased from 0.8 to 6.0 mm screen grinding, in situ starch degradability decreased; the decrease was higher for maize (13.8 points) than for barley (7.4 points) or pea (10.4 points).     

Breakdown of different peptides byPrevotella (Bacteroides) ruminicola and mixed microorganisms from the sheep rumen

Several di-, tri-, and oligopeptides were incubated individually in vitro with rumen fluid from two sheep receiving a mixed grass hay/concentrate diet and with washed cells ofPrevotella (formerlyBacteroides)ruminicola M384 andP. ruminicola B₁4. The rates of breakdown of most peptides were similar in the rumen fluid from the two sheep. Acidic and proline-containing peptides tended to be more slowly degraded than neutral or basic peptides. The dipeptide at the N-terminus of higher peptides was observed as an early product of hydrolysis, confirming that a dipeptidyl aminopeptidase type of activity was present. The relative rates of breakdown of dipeptides byP. ruminicola were different from that of rumen fluid, but the hydrolysis of higher peptides followed a similar pattern, and dipeptides from the N-terminus were detected as early products.     

Consumption of sugars, hemicellulose, starch, pectin and cellulose by the grasshopper Arcris flavolineata

Adults (0.61 g, fresh-weight) of Abracris flavolineata De Geer (Orthoptera: Acrididae) feeding on Brassica oleracea acephala leaves ingest 21 mg dry-weight/day with an approximate digestibility of 42%. Chemical determinations performed on the leaves ingested and on the feces expelled led to the determination of the approximate digestibilities (%) of the major carbohydrates of leaves as follows: soluble carbohydrates, 91; pectin, 32.1; hemicellulose, 0; starch, 66; cellulose, 15. The results are not sufficient to disregard the possibility that digestible hemicellulose polymers contaminate the pectin and the cellulose fraction. Thus, it is possible that the digestibility of hemicellulose is different from zero, and that the digestibility of pectin and cellulose are somewhat lower than reported. The data are used to propose physiological roles of the enzyme activities previously found in the A. flavolineata midgut.