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Interaction of lipid supply and carbohydrates in the diet of sheep with digestibility and ruminal digestion
- Y. Elmeddah, M. Doreau, B. Michalet-Doreau
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- Journal:
- The Journal of Agricultural Science / Volume 116 / Issue 3 / June 1991
- Published online by Cambridge University Press:
- 27 March 2009, pp. 437-445
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Two groups of nine wethers, three of which were fitted with rumen cannulas, were used in a digestion trial at the INRA centre in Theix, France, in 1988. Group 1 received 65% maize silage and 35% concentrates; group 2 received 65% hay and 35% concentrates. Concentrates were based on either cereals rich in starch, or by-products rich in fibre and were given either alone or supplemented with lipids as calcium soaps. The fatty acid content of lipid-supplemented diets was c. 9·5 and 8·5% of dry matter, of which 85 and 89% was provided by calcium soaps, for maize silage and hay diets, respectively. For each group, the four diets were tested in four successive periods from January to June 1988.
Total digestibility of dry and organic matter, acid detergent fibre (ADF) and neutral detergent fibre (NDF) was measured in six wethers of each group by total faeces collection. On cannulated wethers, volatile fatty acid content and composition, pH and NH3-N in rumen liquor were determined four times a day; in sacco degradability of dry matter, ADF and NDF of the forage eaten by the wethers was estimated by the kinetics of incubation in the rumen.
In vivo and in sacco results showed that dry matter and organic matter digestibilities were not modified by the nature of concentrates. Cell wall digestibility was higher for fibre concentrates than for starchy concentrates, by 4·1 and 6·2 percentage units for NDF in maize silage and hay groups, respectively. Volatile fatty acids (VFA) and ammonia concentrations were higher and pH was lower with the maize silage than with the hay diet.
Lipid supply slightly increased cell wall digestibility in the group fed maize silage by 7·5 and 2·0 percentage units for starch and fibre concentrates, respectively. This surprising increase was related to an improvement in in sacco degradability. In all diets, lipid supply increased pH, but variations in VFA concentration and pattern were low. Interactions between the nature of concentrate and lipid supply were moderate, but were higher in the group fed maize silage than in the group fed hay, especially for total digestibility.
Effects of underfeeding and of fish meal supplementation on forage digestion in sheep
- P. Kabré, M. Doreau, B. Michalet-Doreau
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- Journal:
- The Journal of Agricultural Science / Volume 124 / Issue 1 / February 1995
- Published online by Cambridge University Press:
- 27 March 2009, pp. 119-127
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The effects of severe food restriction and of protein supplementation on the apparent digestibility of a forage were studied on 12 wethers in 1992 at INRA, Theix. Ruminal digestion of the forage cell walls was studied in a second experiment carried out on four ewes fitted with rumen and duodenal cannulas, receiving the same diets as the wethers. The animals were fed on two different hay-based diets: hay only (58 or 25 g/kg BW0·75 per day) or hay supplemented with fish meal (48 or 20 g hay with 6·5 and 3·0 g fish meal respectively per kg BW0·75). The effects of fish meal supplementation on apparent digestibility of the hay cell walls were small, + 1·8 and + 2·3 units for neutral detergent fibre (NDF) and acid detergent fibre (ADF) respectively. In contrast, NDF and ADF digestibility was respectively 4·0 and 4·7 units higher at low than at high intake. Rumen fluid volume decreased by 2·4 1 with decreasing intake, while water concentration in rumen content increased slightly from 89·8 to 91·8%. The mean retention time of the hay particles in the foreguts increased concomitantly from 39·5 to 55·1 h. This was achieved by a higher retention time to a similar extent in both slow and fast compartments. The calculated in situ degradability of NDF and ADF increased respectively by 12·1 and 13·1 units with decreasing intake. This reflected the lower fractional outflow rate recorded at low intake. If a fractional outflow rate value of 4·1%/h (as measured in high intake diets) was applied to all dietary treatments, NDF and ADF in situ degradability would be greater at low than at high intake (31·7 v. 26·6% for NDF; 27·9 v. 22·1 % for ADF), indicating a higher microbial activity in restricted diets. Interactions between intake and fish meal supply were detected for in situ degradation parameters, indicating principally a reduction of the cell wall undegraded fraction in supplemented diets when intake declined. Ruminal fermentation was modified by the dietary treatments, the acetate: propionate ratio being higher at low intake. Fish meal increased concentrations of ammonia and of isoacids in rumen liquid. The relationship between apparent digestibility and in situ degradability of plant particles is discussed.
Meta-analysis of 0 to 8 h post-prandial evolution of ruminal pH
- C. Dragomir, D. Sauvant, J.-L. Peyraud, S. Giger-Reverdin, B. Michalet-Doreau
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The objective of this study was to identify relevant descriptors of ruminal pH post-prandial evolution that can replace the mean pH (considered unsatisfactory). These descriptors are to be used in the attempts to predict ruminal pH from dietary characteristics, in order to quantify the potential of a diet to induce subacute ruminal acidosis from its intrinsic characteristics. A total of 219 pH curves, reported as graphics in 48 published articles describing the post-prandial evolution of ruminal pH (first 8 h), were digitized by image analysis then summarized in 15 pH variables. Relationships among pH variables and the principal components (PCs) of pH variability were analyzed in order to identify possible alternatives to mean pH, as the average value of all pH data the curve is composed of. Two groups of pH variables were identified according to their relationship with the most important principal components. A first group, including mean pH, was closely related to PC1, which accounted for 78% of data variability; hence, correlations between variables of this group were generally high. Of these, threshold-related variables were distinct as their within-study correlations with mean pH were rather moderate (0.69 on average). This suggests they might carry supplementary information that could explain the variation in ruminal pH induced by within-study factors, e.g. diet characteristics. However, caution should be taken in their use because of their truncation at 0 h and their non-normal distribution. Variables from the second group were independent of the PC1, and thus of the first group of variables, whereas they were mostly related to PC2 and PC3. This implies they are complementary to mean pH. Of this second group, the rate of pH decreases or the time period when pH reaches its minimum might be useful to better describe the ruminal status, from the point of view of the risk of subacute ruminal acidosis.
Dose effect of live yeasts on rumen microbial communities and fermentations during butyric latent acidosis in sheep: new type of interaction
- L. Brossard, F. Chaucheyras-Durand, B. Michalet-Doreau, C. Martin
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- Journal:
- Animal Science / Volume 82 / Issue 6 / December 2006
- Published online by Cambridge University Press:
- 13 March 2007, pp. 829-836
- Print publication:
- December 2006
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Six ruminal cannulated Texel sheep were used to assess the dose response and the effect of live yeasts (Levucell® SC, Saccharomyces cerevisiae CNCM I-1077) on the prevention of induced ruminal latent acidosis. The sheep received, in a replicated 3×3 Latin-square design, an acidotic diet (wheat +lucerne hay, 60:40 (dry matter (DM) basis); starch: 410 g/kg DM) without yeast (control group; L0 treatment), supplemented with 0·2 g/day yeast (4×109 colony-forming units (c.f.u.) per day corresponding to producer recommendations; L1 treatment) or with 2 g/day yeast (4×1010 c.f.u. per day; L10 treatment). The following measurements were carried out: food intake, ruminal pH, ruminal volatile fatty acids (VFA), lactate and ammonia (NH3) concentrations, protozoal and lactate-utilizing bacterial counts, relative proportions of two main bacteria implicated in lactate metabolism (a lactate-producing species, Streptococcus bovis, and a lactate-utilizing species, Megasphaera elsdenii) using specific 16S-rRNA-targeting oligonucleotide probes, activities of lactate dehydrogenase (LDH) and of polysaccharidases involved in plant cell wall (xylanase, carboxymethylcellulase) and starch (amylase) degradation. The acidotic diet (L0) induced a butyric (12 mol per 100 mol total VFA) rather than lactic (<4 mmol/l) ruminal latent acidosis. Ruminal pH, fermentative patterns, lactate-metabolizing bacteria (concentration, LDH activity) and polysaccharidase activities were similar between treatments (P>0·1). Yeast supplementation tended to increase ruminal protozoal population (P<0·1) and intake of animals (P<0·1). The recommended yeast concentration (L1) was sufficient to ensure these effects. The yeast's action may differ according to the nature and function of the micro-organisms involved and the type of fermentative pattern favoured (protozoa/butyrate v. lactate-metabolizing bacteria/lactate and propionate) during ruminal acidosis in sheep.