Ultraviolet-absorbing compounds in milk are related to forage polyphenols.

The aim of this work was to characterize UV-absorbing compounds (UAC) in milk in relation to diet. In winter, 4 groups of cows each received a different diet: concentrate rich containing 35% cocksfoot hay (CCH), maize silage (MS), rye grass silage (RS), or rye grass hay (RH). In summer, 2 additional diets were given: mountain grassland hay (GH) and mountain grassland pasture (GP). Polyphenols were analyzed by HPLC and Folin reaction on forages and UAC were extracted from milks and analyzed by HPLC. In forages, the number of polyphenols was lowest in MS (57) and greatest in GP (85). Twenty-four peaks were identified, accounting for 28 to 47% peak area at 280 nm. Caffeoyl compounds and flavonoid glycosides were mainly found in RH, GH, and GP. Hydrolyzed compounds such as hydroxycinnamic acids and aglycones were found in MS and RS. Estimated amounts of polyphenols were lowest for MS (3.7 g/kg), roughly similar for CH, RS, and RH (about 15 g/kg), and greatest for GH and GP (21.6 and 35.3 g/kg, respectively). About 230 different peaks were separated in milks. Milks from RH and GP contained the lowest (87) and the greatest (127) numbers of peaks, respectively. Only 10 peaks were identified, accounting for 21 to 54% of the total spectra area. In addition to the major compound hippuric acid, phenylacetic acid, benzoic acid, 4-hydroxybenzoic acid benzaldehyde, catechol, and small amounts of ferulic acid were found in varying amounts depending on the diet. Flavonoids such as quercetin, luteolin, and apigenin were also present. Hippuric acid was clearly related to the presence of caffeoylquinic compounds in forages. Other identified UAC may originate essentially from forage simple polyphenols or from cell wall aromatics. Some of the several unknown compounds may also originate from the transformation of other nutrients. Estimated amounts of UAC were widely variable within each animal group. They were surprisingly high in CCH and roughly similar in all milks from preserved forages (about 3.6 mg/L), with generally greater values for GH milks, whereas the greatest amount was found in GP milks (13.3 mg/L). Hierarchical clustering clearly discriminated the 6 diets, showing that there were major differences in GP milks. Some UAC were specific to one or a group of diets. Ultraviolet-absorbing compounds are therefore a potential tool to distinguish between milks according to diet. In addition, they may have a bioactive effect on milk component conservation or on human health.

Effect of phenolic structures on the degradability of cell walls isolated from newly extended apical internode of tall fescue (Festuca arundinacea Schreb.).

Apical internodes of tall fescue (Festuca arundinacea Schreb. var. Clarine) harvested at flowering were sectioned into 5 or 10 equal parts to study in situ degradability and cell wall composition, respectively. The basal (youngest) section had the greatest primary wall content. Cell walls in the upper (older) sections had the highest xylose/arabinose ratio and lignin content and a lignin rich in syringyl units, all typical of extensive secondary wall development. Almost all of the p-coumaric (p-CA) and about half of the ferulic acid (FA) were released by 1 M NaOH and presumed to be ester-linked. The total FA content was approximately double that of p-CA in all sections other than the youngest with a distribution similar to that of total p-CA. However, the ratio of esterified to ether and ether plus ester linked (Et & Et+Es) FA differed with age. Whereas the esterified form remained essentially constant ( approximately 4.5 g/kg of cell wall), Et & Et+Es ferulate increased with increasing age of the tissue and was significantly related to lignin deposition (r = 0.79, P < 0.01). The extent of cell wall degradation after 48 h of incubation in the rumen was inversely related to maturity, falling from 835 g/kg of dry matter in the youngest section to 396 g/kg in the oldest. Both the rate and extent of cell wall degradation were significantly negatively related to the ratio of xylose to arabinose, lignin content, proportion of syringyl units present in lignin, and concentration of Et & Et+Es FA present. A positive relationship between Et & Et+Es FA was also found, with the rate (P < 0.01) being better correlated than the extent (P < 0.05) of cell wall degradation. Application of the newly extended internode model to fescue produced results consistent with the view that both the lignin content and the extent to which lignin was covalently bound to the other wall polymers crucially influenced the rate and extent of degradation.

Down-regulation of cinnamyl alcohol dehydrogenase in transgenic alfalfa (Medicago sativa L.) and the effect on lignin composition and digestibility.

To improve the digestibility of the forage crop alfalfa (Medicago sativa L.), cinnamyl alcohol dehydrogenase (CAD), which catalyses the last step in the biosynthesis of the lignin monomers, was down-regulated by using an antisense approach. A subset of six transgenic lines with reduced CAD activity and control lines were analysed when grown in the greenhouse and in the field. The down-regulation of the CAD enzyme was associated with a red coloration of the stem. The lignin quantity remained unchanged, but the lignin composition, as determined by thioacidolysis, was altered. The highest reduction of CAD activity was associated with a lower syringyl/guaiacyl (S/G) ratio and a lower S+G yield, mainly because of a decreased amount of S units. An increase in in situ disappearance of dry matter and of cell wall residue was detected in one of the transgenic lines grown in the greenhouse, and for two of the lines grown in the field the rate of disappearance of dry matter slightly improved. Furthermore, these two lines had a higher solubility in alkali as shown by the lower yield of saponified residue. This study opens perspectives for improving forage crop digestibility by the modulation of enzymes involved in lignin biosynthesis.

Net energy value of non-starch polysaccharide isolates (sugarbeet fibre and commercial inulin) and their impact on nutrient digestive utilization in healthy human subjects.

The energy value of NSP has been expressed as their metabolizable energy (ME) content. The aim of the present study was to determine whether differences in ME and net energy (NE) contents were similar for insoluble and soluble NSP. Nine healthy young men were offered three diets according to a Latin-square design (3 x 3) with three repetitions: diet C (control), diet B (control + 50 g sugarbeet fibre/d) and diet I (control + 50 g commercial inulin/d). After a 16 d adaptation period to NSP isolate, food intake was controlled (duplicate meal method) and faeces and urine were collected for 8 d. A period of 60 h was devoted to measurement of energy expenditure (EE) by whole-body indirect calorimetry. NSP-isolate ingestion induced significant increases in the number of defecations and stool weight resulting from increases in water, DM and microbial mass excretion. After deduction of microbial N, differences in faecal N excretion between diets were not significantly different. Urinary N excretion was slightly decreased by sugarbeet fibre or commercial inulin ingestion but the N balances for the diets were not significantly different. Diet energy, N and lipid apparent digestibilities decreased by only 1-2%. Commercial inulin was entirely fermented and fermentability of sugarbeet fibre averaged 0.886 (SD 0.117). Sugarbeet fibre and commercial inulin ME values averaged 10.7 (SD 1.2) and 13.0 (SD 2.3) kJ/g DM respectively. NSP-isolate ingestion caused significant (sugarbeet) and nonsignificant (inulin) increases in daily EE. The maintenance NE contents of sugarbeet fibre and inulin averaged 5.0 (SD 5.0) and 11.9 (SD 1.3) kJ/g DM respectively. Differences in maintenance NE contents of NSP isolates were much greater than differences in ME values.

Transformation of (sup14)C-Lignin-Labeled Cell Walls of Wheat by Syntrophococcus sucromutans, Eubacterium oxidoreducens, and Neocallimastix frontalis.

Wheat cell walls, saponified or not, labeled with [U-(sup14)C]phenylalanine or [O-methyl-(sup14)C]sinapate were fermented by Neocallimastix frontalis or Syntrophococcus sucromutans plus Eubacterium oxidoreducens or a mixed culture. Phenolics were less solubilized but more transformed by bacteria than by the fungus, and mineralization was slight. S. sucromutans O-demethylated [O-methyl-(sup14)C]syringyl lignins, yielding labeled acetate.

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.

[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.

[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.