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Biomedical subjects

E Grenet

Publications and source records attributed to E Grenet.

11 recordsLinked to original sources
PubMed1996

Immunocytochemical localization of arabinoxylans in the cell wall of maize apical internode after microbial degradation in the rumen.

Arabinoxylans were localised by immunocytochemistry using polyclonal antibodies in the cell walls of the apical internode of maize after degradation in the rumen. In order to understand the significance of arabinoxylan in digestibility property, two lines of maize differing in digestibility were used. Wide variations in the intensity of labelling were observed in the four tissues studied (sclerenchyma, fibres, xylem and parenchyma) from the first hours of incubation in the rumen. Incubation time in the rumen greatly influences the intensity of labelling.

Animals↗
PubMed1994

Lignin-carbohydrate complexes in forages: structure and consequences in the ruminal degradation of cell-wall carbohydrates.

Lignin-carbohydrate complexes (LCCs) are recognised as key structures in forage degradability. Apart from ester bonds involving phenolic acids, which seem to play a major role in grasses, little is known about the other types of linkages that must exist but have proved difficult to demonstrate. The chemical nature of possible LCC linkages is presented and the various mechanisms through which LCCs in the cell-wall architecture may interfere with carbohydrate utilisation by rumen microorganisms are discussed.

Animal Feed↗
PubMed1992

Degradation of maize stem by two rumen fungal species, Piromyces communis and Caecomyces communis, in pure cultures or in association with cellulolytic bacteria.

Two species of rumen fungi, Piromyces (Piromonas) communis FL and Caecomyces (Sphaeromonas) communis FG10, were cultured alone or in association with the cellulolytic bacteria Ruminococcus flavefaciens or Fibrobacter succinogenes on maize stem. A kinetic study of the degradation of the substrate was then made. After 48 h of culture, all non-lignified tissues observed by scanning electron microscopy disappeared with P communis and degradation was as complete as that observed in the rumen. In contrast, C communis degraded little of the plant cell walls. The ability of P communis to more rapidly degrade maize stem was probably due to the presence of filamentous rhizoids. The extent of dry matter loss after 8 days of incubation was practically the same in all the monocultures and in the 4 cocultures. However, the rate of degradation was faster in the bacterial than in the fungal monocultures and the co-cultures. No metabolic interaction was observed.

Animals↗
PubMed1991

Microscopic investigation of changes in histology and digestibility in the rumen of a forage grass and a forage legume during the first growth stage.

An Italian "Dalita" ryegrass (Lolium italicum) and a European lucerne (Medicago sativa) were harvested at 5 different growth stages to determine the anatomical factors limiting their digestibility and in particular the effects of lignification of the tissues. In vitro digestibility, cell wall contents of the whole plant and stem of lucerne and of the whole plant, stem and leaf blade of ryegrass were determined. The rate and the extent of degradation in the rumen of the different tissues were observed by scanning electron microscopy. This degradation occurred very rapidly with the lucerne stems; the xylem of lucerne was the only undegradable tissue whatever the stage. The collenchyma was degraded in the rumen although with acid phloroglucinol it stained positive for the presence of phenolic compounds. Ryegrass stems were digested more slowly than lucerne stems, and the sclerenchyma and xylem of ryegrass were indigestible whatever the stage. The parenchyma located close to the sclerenchyma became indigestible as the cell walls lignified progressively from the third stage. These results contribute to the understanding of the decrease in digestibility over the first growth stage and the variation in rate of digestion of lucerne and ryegrass in the rumen.

Animal Feed↗
PubMed1990

Microbial degradation in the rumen of wheat straw and anhydrous ammonia treated wheat straw observed by electron microscopy.

With the exception of the phloem and the crown of the parenchyma, which borders the medullary lacuna, the walls of the tissues of both treated and untreated straw were lignified. The walls of the treated straw were not fluorescent in the ultraviolet probably because the treatment had modified the phenolic acids. They also had a stronger reaction to Schiff reagent particularly in the sclerenchyma indicating that their polysaccharides were more accessible. The tissues of the treated straw degraded faster in the rumen. The walls of the sclerenchyma of the treated straw were attacked by micro-organisms. Both treated and normal straw were abundantly colonized by rumen fungi, especially in the sclerenchyma. The increase in the digestibility of the treated straw was due to the greater access the micro-organisms had to the polysaccharides of the lignified walls.

Ammonia↗
PubMed1989

A comparison of the digestion and reduction in particle size of lucerne hay (Medicago sativa) and Italian ryegrass hay (Lolium italicum) in the ovine digestive tract.

Four types of hay were used: an early-cut and a late-cut lucerne (Medicago sativa) and an early-cut and a late-cut ryegrass (Lolium italicum). Digestibility and voluntary intake were measured on six adult sheep maintained in metabolism crates and fed 10% above the previous day's consumption, in equal portions at 08.00 and 16.30 hours. Lucerne intake was higher than that of ryegrass at similar digestibilities. The rate of digestion of the four hays was measured using nylon bags and the rates of digestion of dry matter for late-cut lucerne were faster than those for the late-cut ryegrass. Eleven adult sheep fitted with oesophageal (four), rumen (four) or duodenal (three) fistulas were used for collecting digesta samples at the different sites. They were fed successively with the four hay types. Each was offered to appetite, once daily, in a meal taken over 4 h. The rumen of rumen-fistulated sheep was completely emptied by hand once before feeding (08.00 hours) and once after removal of refusals (12.00 hours). The number of times the ingested hay was chewed during the meal and the time spent masticating was greater for the late-cut hays and greater for the ryegrass compared with the lucerne hays. The particle size of the boluses was greater than that of the rumen contents, which in turn was greater than that of the duodenal contents and faeces. The percentage of particles greater than 8 mm in the boluses from the ryegrass was higher than that of lucerne, and that of the early-cut ryegrass was greater than that of the late-cut ryegrass. This was also the case for the percentage of particles greater than 1.6 mm in the rumen contents after the meal. The rate at which dry matter disappeared from the rumen was greatest during the meal except with late-cut ryegrass; it was particularly high with late-cut lucerne, a little less with early-cut ryegrass and much lower with the other two hays. When nylon bags containing food boluses were placed in the rumen, it was apparent that without rumination, with the exception of the very digestible early-cut ryegrass, microbial degradation alone did not reduce the particle size.

Animals↗
PubMed1989

Influence of diet and monensin on development of anaerobic fungi in the rumen, duodenum, cecum, and feces of cows.

Three cows with fistulated rumens, duodenums, and ceca were fed five different diets: lucerne hay, lucerne hay plus whey (40:60), lucerne hay plus beets (50:50), corn silage plus monensin (40 ppm [40 g/kg] of dry matter intake), and lucerne hay plus monensin (80 ppm of dry matter intake). The fungal population was observed in the rumen, duodenum, cecum, and rectum and varied with diet; it was most abundant with lucerne hay alone and with corn silage plus monensin. The proportion of particles colonized by fungi in the duodenum, the cecum, and feces was measured by microscopic observation and varied from 5 to 50%, depending on the diet. The further sporangia attached to the plant particles were from the rumen, the more likely they were to be devoid of spores. Results confirmed the influence of diet on the development of the ruminal fungal population and showed that monensin does not eliminate these microorganisms. They also confirmed the presence of anaerobic fungi in the ruminant intestine. It is likely that anaerobic fungi leave the rumen attached to plant particles. However, large colonies of nonrhizoidal-type fungi were observed in cecum samples and in feces; at these sites, environmental conditions are perhaps more favorable for this type of fungus than they are in the rumen.

Anaerobiosis↗
PubMed1987

Energy utilization of sodium hydroxide treated or untreated straw supplemented with protein or concentrates by adult sheep. 2. Rumen digestion.

NaOH treated (T) or untreated (UT) barley straws were supplemented either with protein (P) or with concentrates based on maize (M) or beet pulp (BP), the two last at rates of 25 and 50% of the diet. Each of the 10 diets was fed to two sheep ad libitum. Two diets were also fed at limited intakes. For these 12 diets in sacco cellulolytic activity in the rumen and ruminal fermentation were measured. Cellulolytic activity was measured with the studied straws, so that their digestion rate was also determined. NaOH treatment increased rate of digestion of straw, while high levels of concentrates decreased it. In contrast NaOH treatment and high levels of concentrate decreased cellulolytic activity but neither type of concentrate nor limitation of intake altered it. NaOH treatment only slightly modified pH because a higher level of VFA in rumen balanced NaOH presence. An important negative effect on pH of high levels of concentrate was observed, but there was no effect or type of concentrate or limitation of intake. Fermentation pattern was only slightly influenced by studied factors: +2.2 units of butyric acid and -2.1 units of acetic acid with treated straw; lower level of acetic acid occurred when concentrate was increased, especially for maize. Limitation of intake increased acetic acid molar proportion.

Ammonia↗