Evaluation of the factors affecting silage intake of dairy cows: a revision of the relative silage dry-matter intake index

An evaluation of the factors affecting silage dry-matter intake (SDMI) of dairy cows was conducted based on dietary treatment means. The data were divided into six subsets based on the silage treatments used in the experiments: concentration of digestible organic matter in dry matter (D-value) influenced by the maturity of grass ensiled (n = 81), fermentation quality influenced by silage additives (n = 240), dry matter (DM) concentration influenced by wilting of grass prior to ensiling (W; n = 85), comparison of silages made from primary growth or regrowth of grass (n = 46), and replacement of grass silage with legume (L; n = 53) or fermented whole-crop cereal (WC; n = 37) silages. The data were subjected to the mixed model regression analysis. Both silage D-value and fermentation quality significantly affected SDMI. The average effects of D-value and total acid (TA) concentration were 17.0 g and − 12.8 per 1 g/kg DM, respectively. At a given D-value, silage neutral-detergent fibre (NDF) concentration tended to decrease SDMI. Silage TA concentration was the best fermentation parameter predicting SDMI. Adding other parameters into the multivariate models did not improve the fit and the slopes of the other parameters remained insignificant. Total NDF intake was curvilinearly related to silage D-value the maximum intake being reached at a D-value of 640 g/kg DM. Results imply that physical fill is not limiting SDMI of highly digestible grass silages and that both physical and metabolic factors constrain total DM intake in an interactive manner. Silage DM concentration had an independent curvilinear effect on SDMI. Replacing primary growth silage with regrowth, L or WC silages affected SDMI significantly, the response to regrowth silage being linearly decreasing and to L and WC quadratically increasing. The outcome of factors affecting SDMI was used to update the relative SDMI index as follows: SDMI index = 100+10 × [(D-value − 680) × 0.0170 − (TA − 80) × 0.0128+(0.0198 ×  (DM − 250) − 0.00002364 × (DM² − 250 ²)) − 0.44 × a+4.13 × b − 2.58 × b²+5.90 × c − 6.14 × c² − 0.0023 × (550 − NDF)], where a, b and c represent the proportions (0–1) of regrowth, L or WC silages from total silage DM. For the whole data set, one index unit corresponded to the default value of 0.10 kg in SDMI. The SDMI index explained proportionally 0.852 of the variation in SDMI with 0.34 kg DM per day residual. The updated SDMI index provides improved basis for the practical dairy cow ration formulation and economic evaluation.     

13种沙生植物纤维和导管分子长度变异的研究及木质部特征的定量研究

对13种沙生植物的纤维长和导管分子长度进行了测定分析, 二者的径向变异规律呈现上升,下降, 波动或恒定不变趋势。所选树种的平均纤维长度小于900 μm,属于较短纤维。所选树种的纤维长度和导管分子长度除沙冬青年轮内差异不显著外,其他树种间及树种年轮间的差异极其显著。对沙生植物的解剖特征的定量研究可以看出,所选树种的次生木质部特征体现了对沙漠环境的高度适应性。较短,孔径较窄导管以单管孔或复管孔形态出现,纹孔较小使干旱区沙生植物具有较大的水分运输能力,也是水分安全传导的一种策略。     

Characterization of a lignified secondary phloem fibre-deficient mutant of jute (Corchorus capsularis)

BACKGROUND AND AIMS: High lignin content of lignocellulose jute fibre does not favour its utilization in making finer fabrics and other value-added products. To aid the development of low-lignin jute fibre, this study aimed to identify a phloem fibre mutant with reduced lignin. METHODS: An x-ray-induced mutant line (CMU) of jute (Corchorus capsularis) was morphologically evaluated and the accession (CMU 013) with the most undulated phenotype was compared with its normal parent (JRC 212) for its growth, secondary fibre development and lignification of the fibre cell wall. KEY RESULTS: The normal and mutant plants showed similar leaf photosynthetic rates. The mutant grew more slowly, had shorter internodes and yielded much less fibre after retting. The fibre of the mutant contained 50 % less lignin but comparatively more cellulose than that of the normal type. Differentiation of primary and secondary vascular tissues throughout the CMU 013 stem was regular but it did not have secondary phloem fibre bundles as in JRC 212. Instead, a few thin-walled, less lignified fibre cells formed uni- or biseriate radial rows within the phloem wedges of the middle stem. The lower and earliest developed part of the mutant stem had no lignified fibre cells. This developmental deficiency in lignification of fibre cells was correlated to a similar deficiency in phenylalanine ammonia lyase activity, but not peroxidase activity, in the bark tissue along the stem axis. In spite of severe reduction in lignin synthesis in the phloem cells this mutant functioned normally and bred true. CONCLUSIONS: In view of the observations made, the mutant is designated as deficient lignified phloem fibre (dlpf). This mutant may be utilized to engineer low-lignin jute fibre strains and may also serve as a model to study the positional information that coordinates secondary wall thickening of fibre cells.     

Mechanisms by which resistant starches and non-starch polysaccharide sources affect the metabolism and disposition of the food carcinogen, 2-amino-3-methylimidazo[4,5-f]quinoline

Although both non-starch polysaccharides (NSP) and resistant starches (RS) are included in current definitions of dietary fibre, our previous work has suggested fundamental differences in the way in which these two classes of material affect the disposition and absorption of a dietary carcinogen. The present studies explore whether different effects on carcinogen metabolism could play a role in the contrasting patterns seen previously. Groups of female Wistar rats were pre-fed for 4 weeks one of five types of defined diet (AIN-76). The control diet contained 35% maize starch and no dietary fibre. The RS-containing diets had all the maize starch substituted with either Hi-maize or potato starch. In the NSP-containing diets, 10% of the maize starch was substituted with dietary fibre in the form of either lignified plant cell walls (wheat straw) or soluble dietary fibre (apple pectin). Pre-fed rats were gavaged with the food carcinogen, [2-14C] 2-amino-3-methylimidazo[4,5-f]quinoline (IQ), and plasma and urinary metabolites characterized using HPLC at various time intervals after administration. After 4 h gavage, plasma from rats on both RS-containing diets contained significantly higher levels of intact IQ and lower levels of the major metabolites, IQ-5-O-glucuronide and IQ-5-sulfate, as compared with plasma from the negative control group at this time. In contrast, plasma from animals on the NSP-containing wheat straw diet (and to a lesser extent the apple pectin diet) showed significantly lower levels of intact IQ, and significantly higher levels of the two major metabolites, as compared with those from the control rats. These different metabolite profiles were also reflected in different urinary excretion profiles. Urine from rats pre-fed RS-containing diets revealed significantly slower metabolite excretion as compared with urine from rats that had been given the NSP-containing diets. Western blotting methodologies also profiled differences between the effects of these two types of dietary fibre in the expression of xenobiotic metabolizing enzymes. We conclude that changes in activity and expression of xenobiotic metabolising enzymes could play a role in the contrasting effects of these two types of dietary fibre on carcinogen uptake and disposition.     

Ca(2+) -independent vesicular catecholamine release in PC12 cells by nanomolar concentrations of Pb(2+)

Effects of Pb(2+) on vesicular catecholamine release in intact and ionomycin-permeabilized PC12 cells were investigated using carbon fibre microelectrode amperometry. Changes in intracellular Pb(2+) and Ca(2+) were measured from indo-1 fluorescence by confocal laser scanning microscopy. Depolarization of intact cells and superfusion of permeabilized cells with saline containing > or = 100 microm Ca(2+) rapidly evokes quantal catecholamine release. Superfusion with up to 10 microm Pb(2+) -containing saline evokes release of similar catecholamine quanta after a concentration-dependent delay. Thresholds to induce exocytosis within 30 min of exposure are between 1 and 10 microm Pb(2+) in intact cells and between 10 and 30 nm Pb(2+) in permeabilized cells. Additional inhibition of exocytosis occurs in permeabilized cells exposed to 10 microm Pb(2+). Using membrane-impermeable and -permeable chelators it is demonstrated that intracellular Ca(2+) is not required for Pb(2+) -induced exocytosis. In indo- 1-loaded cells Pb(2+) reduces the fluorescence intensity after a concentration-dependent delay, whereas the fluorescence ratio, indicating intracellular Ca(2+) concentration, remains unchanged. The delay to detect an increase in free intracellular Pb(2+) (> or = 30 nm) is much longer than the delay to Pb(2+) -induced exocytosis, indicating that cytoplasmic components buffer Pb(2+) with high affinity. It is concluded that Pb(2+) acts as a high-affinity substitute for Ca(2+) to trigger essential steps leading to vesicular catecholamine release, which occurs when only approximately 20% of the intracellular high-affinity binding capacity ( approximately 2 attomol/cell) is saturated with Pb(2+).     

Effect of dietary fibres on constituents of complex carbohydrates in streptozotocin induced diabetic rat tissues

The effect of dietary fibres on constituents of complex carbohydrates in various tissues of streptozotocin induced diabetic rats is presented by analysing different constituents of complex carbohydrates in presence and absence of dietary fibre. Wheat bran was effective in preventing the decrease (14%) in total sugars in spleen and an increase in total sugars in stomach (33%) during diabetes. Decrease in uronic acid content during diabetes in spleen was prevented to the extent of 25% by the presence of wheat bran in the diet. The other parameters which were affected by the presence of wheat bran in the diet during diabetes are amino sugar (brain and stomach), sulphates (liver) and protein (lungs and stomach). Guar gum was effective in preventing the decrease in total sugar content in spleen by 28% and sulphate content in liver by 14% during diabetes. Variation in protein content in lungs was observed in diabetes. The results indicated beneficial role of dietary fibres like wheat bran and guar gum on complex carbohydrates to varying extents in different tissues.     

Secondary cell wall deposition causes radial growth of fibre cells in the maturation zone of elongating tall fescue leaf blades

A gradient of development consisting of successive zones of cell division, cell elongation and cell maturation occurs along the longitudinal axis of elongating leaf blades of tall fescue (Festuca arundinacea Schreb.), a C3 grass. An increase in specific leaf weight (SLW; dry weight per unit leaf area) in the maturation region has been hypothesized to result from deposition of secondary cell walls in structural tissues. Our objective was to measure the transverse cell wall area (CWA) associated with the increase in SLW, which occurs following the cessation of leaf blade elongation at about 25 mm distal to the ligule. Digital image analysis of transverse sections at 5, 15, 45, 75 and 105 mm distal to the ligule was used to determine cell number, cell area and protoplast area of structural tissues, namely fibre bundles, mestome sheaths and xylem vessel elements, along the developmental gradient. Cell diameter, protoplast diameter and area, and cell wall thickness and area of fibre bundle cells were calculated from these data. CWA of structural tissues increased in sections up to 75 mm distal to the ligule, confirming the role of cell wall deposition in the increase in SLW (r2 = 0.924; P < or = 0.01). However, protoplast diameter of fibre cells did not decrease significantly as CWA increased, although mean thickness of fibre cell walls increased by 95 % between 15 and 105 mm distal to the ligule. Therefore, secondary cell wall deposition in fibre bundles of tall fescue leaf blades resulted in continued radial expansion of fibre cells rather than in a decrease in protoplast diameter.     

Nitrogen availability influences the biochemical composition and photosynthesis of tank-cultivated Ulva rigida (Chlorophyta)

Physiological and biochemical changes in relation to inorganic nitrogen availability were studied for tank-cultivated Ulva rigida grown under nitrogen- enriched and nitrogen-depleted seawater. U. rigida was initially cultivated in nitrogen-enriched seawater (daily concentrations of NH4+ and NO3- + NO2- ranged between 0.5–1.7 and 0.06–0.15 mg L-1, respectively), then transferred to nitrogen-depleted seawater where photosynthetic capacity decreased to zero after 23 d. At the time (14 d) when photosynthetic rates were lower than 2.0 μmol O2 g-1 FW min-1 and strong bleaching had occurred, some algae were returned to the initial nitrogen-enriched seawater to study recovery from N-limited growth. Data on biochemical composition (chlorophylls, ash, caloric content, fatty acids and dietary fibres) and colouration varied significantly depending on the nitrogen conditions. C:N ratios correlated significantly with biochemical parameters. Fatty acid (FA) synthesis continued during the N-starvation period; saturated and mono-unsaturated FA increased to a maximun of 72.2%, while poly-unsaturated fatty acids (PUFA) decreased to 27.7%. During the N-enriched recovery period, the reverse was found. C:N ratios above 10 correlated with carbohydrate synthesis as shown by the dietary fibre level. Under nitrogen enriched conditions, C:N ratios decreased along with a decrease in fibre level. Under controlled conditions, nitrogen represents a major influence on the development of intensive tank cultivation of Ulva rigida, not only by affecting parameters closely related to nitrogen metabolism but also some clearly influenced by carbon uptake. This revised version was published online in June 2006 with corrections to the Cover Date.     

The characterization of Tasmanian devil Sarcophilius harrisii pelage fibres and their associated lipids

The Tasmanian devil (Sarcophilius harrisii) is the largest living marsupial carnivore left on Earth. In this paper we report the results of the first thorough characterization of the keratin fibres comprising the Tasmanian devil pelage. The fibre's morphology, structure, composition and surface have been investigated. The results have been compared with those of a number of other mammalian species including carnivores and herbivores. The fibres structure was found to be consistent with that expected for a keratin fibre. From the results of the bound lipid analysis it can be concluded that the Tasmanian devil is a typical mammal in which the 21‐carbon atom anteiso branched fatty acid is the predominant bound fatty acid. This is consistent with the Tasmanian devil's position in the mammalian phylogenetic tree. The amino acid analysis places the devil in line with other carnivores. The high cystine and proline content may correlate with the Tasmanian devil's diet which is rich in muscle and collagen proteins.     

Novel 16S rRNA gene analyses reveal new in vitro effects of insoluble barley fibres on the human faecal microbiota

Aims:  The aim of this work was to analyse the growth of human faecal microbiota on barley dietary fibres (DF). It is generally accepted that insoluble DF are health promoting, but the information is scarce about how these fibres affect the gastrointestinal (GI) microbiota. A major reason for the limited knowledge is that there are currently no proper tools to analyse the complete GI microbiota.
Methods and Results:  Here we present a novel 16S rRNA gene analytical approach that enables the analyses of the complete microbiota, including the part that has not yet been characterized. The basic principle of the method is use of 16S rRNA gene signature sequences to determine both the phylogenetic relatedness and the distribution of bacteria in the samples analysed.
Using this approach, we analysed the microbiota after in vitro fermentation of different barley fractions with human faeces. Our main finding was that groups of actinobacteria were selectively enriched by growth on the insoluble DF fractions.
Conclusions:  Our novel analytical approaches revealed new enrichment patterns in the taxa that respond to insoluble DF.
Significance and Impact of the Study:  Our results may have major implications for future understanding of insoluble DF health effects.