Role of rumen protozoa in nitrogen digestion in sheep given two isonitrogenous diets.

1. The effect of protozoa on digestion in the rumen was studied using either defaunated or faunated sheep. 2. Six wethers, each fitted with rumen and simple duodenal cannulas, were given two isonitrogenous diets containing either lucerne (Medicago sativa) hay (diet L) or sodium hydroxide-treated wheat straw (diet S). The diets were given in eight equal portions per day at 3-h intervals. The mean intake of dry matter, 53 g/kg body-weight0.75 per d, was similar for the two diets and each diet had a similar digestible organic matter content. Diet L promoted a large protozoal population and was rich in nitrogen sources of low rumen-degradability, while diet S supported a smaller protozoal population and was rich in rumen-degradable N. 3. Digesta flow at the duodenum was estimated by means of a dual-marker technique using chromium-mordanted lucerne hay and polyethylene glycol as markers. The microbial flow at the duodenum was estimated using diaminopimelic acid (DAPA), nucleic-acid purine bases (PB) and 35S incorporation simultaneously. The different microbial markers were compared in the defaunated sheep. Protozoal N contribution was estimated in faunated sheep. 4. Defaunated sheep had lower rumen ammonia concentrations and molar proportions of butyric acid than faunated sheep, but they had higher molar proportions of propionic acid. 5. Rumen organic matter digestion was reduced by defaunation, but this decrease was compensated for by increased intestinal digestion. 6. There was a net increase of N flow (approximately 10 g/d) between mouth and duodenum in defaunated sheep. This was explained by increases in both microbial and dietary N flows from the rumen compared with faunated sheep. 7. The influence of protozoa on solid- and liquid-phase retention times in the rumen is discussed, as well as the protozoal contribution to microbial N flow in the duodenum of faunated sheep.

Colonic metabolism of wheat starch in healthy humans. Effects on fecal outputs and clinical symptoms.

To study the intracolonic digestion of starch, 5 healthy volunteers were maintained on a constant diet for 7 days. On the fourth day, the cecum was intubated and a suspension of raw wheat starch (50 g, in 500 ml of 154 mM NaCl and containing 10 g of polyethylene glycol 4000) was infused into the distal ileum at 2 ml/min. Hydrogen excretion in breath was measured, cecal contents were sampled, and symptoms were recorded. For the 2-3 days before and after starch infusions, fecal weight, pH, and percentage of dry matter were monitored; fecal outputs of starch, volatile fatty acids, lactic acid, ethanol, polyethylene glycol, alpha-amylase, nitrogen, and ammonia were also measured. A lactulose (10 g) hydrogen breath test was performed 5-7 days after the starch infusions. After the infusion of starch, concentrations of lactic and volatile fatty acids increased and pH decreased markedly in cecal contents. None of the fecal values changed significantly after starch, however, indicating that carbohydrate catabolism was nearly complete and that the colon absorbed the catabolic products efficiently. Abdominal symptoms, especially bloating, were noted by all subjects, and 2 subjects complained of cramping pain. No subject experienced diarrhea. The amounts of starch metabolized in the colon (47.3 +/- 2.9 g), as calculated from the excretion of H2 in breath compared to the hydrogen breath test after lactulose, were close to the actual load (50 g).

[The rumen fermenter]. / Le fermenteur rumen.

The two main pregastric compartments of ruminants (rumen and reticulum) can be compared to an anaerobic fermenter which allows them to use energetic and nitrogen substrates which are indigestible by monogastric animals. The aim of this bibliographic review is to describe the main features (characteristics) of this fermenter, focusing on the role of microbes (bacteria, protozoa and fungi), on the degradation of cell-wall carbohydrates (cellulose, hemicelluloses, pectic substances), on nitrogen digestion and finally on the utilisation of the major minerals and trace elements.

Effect of lasalocid sodium on rumen fermentation and digestion in sheep.

Four adult sheep were fed 4 diets successively according to a Latin-square design. They were fitted with a rumen cannula and with simple cannulae at the duodenum and ileum. The basal diet (L0) was composed of highly-pressed ensiled sugar beet pulp (56.2%), cereal (barley and corn: 27.6%), urea (1.5%) and wheat straw (14.1%). Lasalocid sodium was added to obtain the following respective amounts: 21 ppm for diet L1, 43 ppm for diet L2 and 64 ppm for diet L3 (table 1). In the rumen, lasalocid significantly increased the molar proportion of propionic acid in the volatile fatty acids (VFA) mixture at the expense of the acetic and butyric acid proportions. The total VFA concentration decreased, especially with 43 and 64 ppm (table 2). Accordingly, the proportion of methane in rumen gases decreased. The ciliate population was always lower in animals fed experimental diets L1, L2, and particularly L3. The non-food-particle-associated bacterial population also decreased; the differences were significant only with the highest doses of lasalocid (L3). At the same time, bacterial cellulolytic activity increased 10%, indicating that qualitative modifications had taken place in the rumen bacterial population (table 3). Overall digestive utilization of organic matter (OM) decreased when lasalocid was added to the diets. This was due to a considerable reduction in forestomach digestion (12% decrease) (table 4). A greater supply of OM rich in cell-wall carbohydrates in the duodenum would explain the lower digestibility in the small intestine of animals given diet L1 and especially the L2 and L3 diets. No significant shift in digestion was noted in the large intestine. The composition of the non-ammonia nitrogen that entered the duodenum of sheep given lasalocid differed from that noted with the control diet (L0) (table 5). The amount of microbial proteins was significantly lower, whilst the proportion of non-degraded feed proteins was higher. The efficiency of microbial synthesis (bacterial proteins/kg OM truly digested in the rumen) was not significantly modified by lasalocid. All these modifications in digestion observed with these diets, and resulting from changes in the qualitative and quantitative composition of flora and fauna in the rumen, have an effect on nitrogen and energy utilization in the ruminant.

A descriptive study of rumen digestion in meroxenic lambs according to the nature and complexity of the microflora.

We studied in meroxenic lambs, i.e. in lambs with a simplified digestive microflora, the effect of the microflora on the quantities of solid feed intake and on the main digestive parameters in the rumen. Axenic lambs were inoculated with a more or less complex flora, obtained by diluting (10(-8), 10(-7), 10(-8) a pool of rumen fluid taken either from young conventional lambs before weaning from adult sheep (Pool A) or from meroxenic lambs (Pool B). A few of these lambs then were inoculated with a genus of protozoa (Entodinium sp. or Polyplastron multivesiculatum). The results show that the main digestive parameters depended on the nature of the inocula which the lambs had received. Food consumption and volatile fatty acid concentration of the rumen fluid, low in lambs inoculated with the 10(-8) dilution, were higher in lambs inoculated with a more complex microflora (10(-6) and 10(-7) dilutions). The VFA concentration measured in these lambs however was approximately two times lower than that observed in conventional animals at the same age and fed the same feed. Food intake and the development of the fermentation pattern were favoured by an early inoculation of the animals. The complexity of the microflora appears to have influenced the composition of the VFA mixture. The latter was found to consist mainly of acetic acid in lambs inoculated with the 10(-8) dilution. In lambs which received the 10(-6) dilution, the composition of the VFA mixture was similar to that observed in conventional lambs. In all animals, except in lambs 10(-8), the ammonia nitrogen concentration of the rumen fluid was found to be higher during the first month after birth (between 100 and 200 mg/l). A subsequent decrease in ammonia nitrogen concentration was observed at two and a half months of age (20 to 40 mg/l). The establishment of protozoa ciliates in the rumen of these lambs was followed by an increase in butyric acid and ammonia nitrogen concentration.

[Qualitative aspects of intestinal digestion of soybean cake carbohydrates in the preruminant calf]. / Aspects qualitatifs de la digestion intestinale des glucides d'un tourteau de soja par le veau préruminant.

Two 15-day old preruminant calves, fitted with reentrant ileocaecal and single colon cannulae, were fed a milk substitute containing 47 p. 100 of toasted soya oil meal, 17 p. 100 of crystallized tallow, 28.5 p. 100 of lactose, 7.0 p. 100 of minerals plus vitamins and 0.5 p. 100 of DL-methionine all on a dry basis. Samples from the ileum, colon and faeces were collected every 2 hrs for 8 hrs after feeding, when the calves 1 and 2 were 4 and 9 week-old, respectively. Total water-soluble carbohydrates were determined, then identified by ion-exchange chromatography. In this preliminary work, we only present results on the healthiest calf. At the end of the small intestine, sucrose and alpha-galactosides were probably poorly digested. Their concentration (as a percentage of total water-soluble carbohydrates) was the same as in the soya bean. In the large intestine, these carbohydrates were completely utilized and the sucrose was break down faster than the alpha-galactosides. The end product of fermentation was mainly lactic acid (4-8 g/l of intestinal contents), and the pH values of the large intestine contents were low (4.0-4.9), but these fermentations did not cause digestive problems, such as diarrhea, probably because the amount of soya carbohydrates in the food was low, and the digestive processes along the digestive tract were very regular.

[Digestion of alkane yeast carbohydrates by the preruminant calf]. / Digestion des glucides de la levure d'alcanes par le veau préruminant.

Four 15-day old preruminant calves were fitted with two single cannulae, one in the lower ileum and the other in the upper colon. They were fed (on dry-matter basis) a milk substitute containing 35 p. 100 of dried, defatted, micronized alkane yeast (Candida tropicalis). Yeast carbohydrate digestion was studied in the ileum, colon and feces of two calves at 48, 72 and 102 days of age (three periods), using 1 p. 100 of chromic oxide in the diet as a marker. During each period, samples were collected every 2 hours and then pooled to obtain a sample from each part of the digestive tract. The carbohydrates were separated into 40 degrees C water-soluble (neutral and non-neutral) and water-insoluble fractions (fig. 1), and the composition of each was determined by hydrolysis and ion-exchange chromatography. The alkane yeast contained almost 22 p. 100 (in DM) of carbohydrate (table 1), mainly composed of 7.5 p. 100 of non-soluble mannans and 10.1 p. 100 of glucans, both from the hull, and 0.3 p. 100 of soluble galactans. The total carbohydrate content (table 2) was high in the ileum (23 to 28 p. 100 of DM) and low in the feces (3 to 8 p. 100 of DM). At the end of the small intestine, the soluble fraction contained some mannans and galactans partly bonded with non-carbohydrate compounds, but mainly neutral glucans (fig. 2). The apparent digestibilities (table 3, fig. 3) varied between animals and increased with age (total yeast carbohydrates: calf: 0.53 to 0.75; calf 2: 0.62 to 0.85). Mannans were better digested than glucans (calf 2: 0.95 and 0.57, respectively, at 102 days); the galactans were completely digested.