Article

Klason lignin is a nutritionally heterogeneous fraction unsuitable for prediction of forage neutral detergent fibre digestibility in ruminants

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  • AgModels Foundation
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Abstract

Although lignin has been negatively correlated with neutral detergent fibre (NDF) digestibility (NDFD) in ruminants and used to predict potential extent of NDF digestion of forages, selection of an analysis, Klason lignin (KL) or acid detergent lignin (ADL), to describe the nutritionally relevant lignin has not been resolved. Dismissed as an artifact is the difference between KL and ADL (∆L). A question is whether ∆L influences digestibility of NDF. We evaluated the relationships of ∆L, KL, and ADL with NDFD in order to determine the nutritionally homogeneous or heterogeneous nature of KL. Data sets from 2 laboratories (DS1, DS2) were used that included ADL, KL, and in vitro NDFD at 48 h (NDFD48). DS1 contained 7 C 3 grasses, 17 C 4 maize forages and 19 alfalfas, and DS2 had 15 C 3 grasses, 8 C 4 forages, and 6 alfalfas. Mean ∆L was greater than ADL in C 3 and C 4 samples, and less in alfalfas. Within forage type and laboratory, ∆L was not correlated with NDFD48 (r = -0.34 to 0.49; all P>0.17). ADL was more consistently correlated with NDFD48 (r = -0.47 to -0.95; P <0.01-0.21) than was KL (r = 0.03 to -0.91; P < 0.01-0.94). ∆L as a proportion of KL was correlated with NDFD48 in C 3 and C 4 samples (r = 0.44 to 0.76; P <0.01-0.08). The differing behaviors of ∆L and ADL relative to NDFD48 indicate that KL is a nutritionally heterogeneous fraction, the behavior of which may vary by forage type and ratios of ADL and ∆L present.

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... In a recent study, Van Soest et al. (2020) describes the importance of the variable ΔL, which in theory would consist of acid soluble lignin, phenolic and ferulic acid and protein bound to lignin. A physical characteristic of ΔL is its solubility in some systems, and that part of this portion could be digestible (Gaillard and Richards, 1975). ...
... A physical characteristic of ΔL is its solubility in some systems, and that part of this portion could be digestible (Gaillard and Richards, 1975). Van Soest et al. (2020) found a positive relationship between ΔL/KL with the in vitro 48 h dNDF and concluded no inhibitory effects of ΔL on dNDF, even though soluble lignin that is part of KL is GCS = grass-clover silage, WCM = whole crop maize, RSE = residual standard error, KL = Klason lignin, NDF = neutral detergent fibre, ADF = acid detergent fibre, ADL = acid detergent lignin, NCP = non cellulose polysaccharides, Cel = cellulose Rha = rhamnose, Fuc = fucose, Ara = arabinose, Glu = glucose, Man = mannose, Gal = galactose. iNDF obtained with 288 h in situ rumen incubation. ...
... Raffrenato et al. (2017) also suggested that ether and ester bonds could be formed but with incomplete polymerization hence a reduced effect on digestibility explaining the positive relationship with dNDF in immature grasses. Van Soest et al. (2020) found increasing ADL concentrations associated with a decrease the ΔL/KL ratio, suggesting a conversion of ΔL to ADL with unaffected KL as they mature. However, the maize stem data in the present study had no information on ADL concentration to confirm this hypothesis. ...
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... Both will be analyzed to evaluate proximate compositions such as moisture, crude lipid, ash, crude fiber, and crude proteins, according to Aganduk et al. (2023). Meanwhile, the acid detergent fiber (ADF) and neutral detergent fiber (NDF) contents were evaluated according to the methodology described by Van Soest et al. (2020). This technique involves using a mild detergent to eliminate protein and hemicellulose from the sample. ...
... The utilization of shrubs and woody plants in livestock diets has been shown to increase rumen metabolite richness compared to diets based on traditional forage sources (57)(58)(59). Studies showed that feeding goats on Acacia saligna, a shrub species, led to increased diversity and richness of rumen metabolites compared to a control diet based on alfalfa hay (60)(61)(62)(63). The composition of the plant diet can have significant impacts on the production of metabolites in the rumen. ...
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... Тому першим етапом обміну речовин між організмом тварини і навколишнім середовищем є підготовка інгредієнтів корму до засвоєння, тобто перетравлення. Клітковина є важливою частиною метаболізму у рубці, нестача вуглеводів в раціонах ВРХ призводить до розщеплення жирів тіла з утворенням підвищеної кількості ацетооцтової та βоксимасляної кислот та ацетону, призводячи до захворювань тварин на кетоз [13]. Клітковина як основний некрохмальний полісахарид є необхідним елементом живлення сільськогосподарських тварин, що забезпечує нормальну моторику шлунково-кишкового тракту, утворення в рубці летких жирних кислот, необхідних для синтезу молочного жиру. ...
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... Lignins can be divided into several types in terms of structure. Tese include organosolv lignin, which is obtained from wood processing by the use of liquid organic solvents to treat wood chips [12]; Klason lignin, which is produced from the acid hydrolysis of wood [13]; and sulfonated lignin, which is a nontoxic polymer derived from black liquor [14]. Calcium lignosulfonate (CLS) is a brownish powdery amorphous polymer composed of phenylpropane units, which is created as a byproduct in the sulfte pulping process for producing paper from softwood. ...
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... Norris et al. (2001a) reported 19.6% and 32.3% lignin in ERC foliage and roots, respectively, compared with 5.96% and 16.4% for big bluestem (Andropogon gerardii Vitman) foliage and roots, respectively. Lignin content in corn stover ranges from 15% to 21%, in soybean stems from 13% to 17%, and for C3 or C4 forages and alfalfa from 7% to 14% (Jenkinson, 1981;Buranov & Mazza, 2008;Peltier et al., 2009;Van Soest et al., 2020). Higher amounts of lignin in the tree biomass would likely lead to slower decomposition of ERC inputs as compared with the herbaceous plant materials with lower lignin content in the adjacent fields. ...
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... Straw can be absorbed and utilized by livestock such as cattle and sheep due to the high crude fiber content (30%-40%) and nutrient-rich cellulose, hemicellulose and lignin [19][20][21][22]. Physical treatment, chemical treatment and biological treatment [23][24][25][26] are usually used to treat crop straw to improve the nutritional value of straw and reduce the waste of straw feed resources, so as to achieve the goal of green economy and sustainable development. ...
... Using lignin as an example, the concentration of lignin in animal feeds is frequently determined through the sequential extraction of a feed sample in acid detergent and then 72% sulfuric acid (Van Soest, 1963;AOAC, 1990;Hintz et al., 1996). However, the concentration of lignin in animal feeds can also be determined using other empirical methods, such as the extraction of lignin using acetyl bromide (Ferreira et al., 2021) or the Klason method (Theander et al., 1995;Van Soest et al., 2020). Given that the analytes measured by these 3 methods are different, the analyte cannot be called "lignin" indistinctly. ...
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A rapid method for simultaneous determination of furfural and hydroxymethylfurfural (HMF) in the filtrate of an acidic treatment of biomass was developed based on UV spectrophotometer. Interference from acid soluble lignin is alleviated by the use of absorbance difference spectrum before and after reduction with sodium borohydride (NaBH4). The concentrations of furfural and HMF in the filtrate are determined by measuring the absorbance of the difference spectrum at 277 nm and 285 nm, the characteristic absorption maxima for furfural and HMF, respectively. Two simultaneous equations are solved to obtain the concentrations of furfural and HMF in the filtrate. Acid soluble lignin in the solution is determined to cause negligible interference on the analysis.
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A joint AOAC/American Association of Cereal Chemists (AACC) collaborative study was conducted to determine by the Uppsala method the dietary fiber content and its composition in various foods. The method includes preparation of a residue by treatment with thermostable alpha-amylase and amyloglucosidase and then ethanol precipitation of solubilized dietary fiber components while leaving low-molecular weight carbohydrates in solution. After acid hydrolysis of residue, neutral polysaccharide residues are determined as alditol acetates by gas-liquid chromatography, uronic acid residues are determined by colorimetry, and ash-free acid-insoluble residue (Klason lignin) is determined gravimetrically. Total dietary fiber, including enzyme-resistant starch, is calculated as the sum of nonstarch polysaccharide residues and Klason lignin. Nine laboratories completed the study, analyzing in duplicate 8 unknown dried products that included 4 cereal products, green peas, potato fiber, carrots, and apples. Total dietary fiber contents of products tested ranged from 4.6 to 84.3%, with an average RSDR value of 8.4% (range, 4.8-11.1%). Total neutral polysaccharide residues ranged from 3.8 to 64.1%, with an average RSDR value of 7.5% (range, 5.4-10.5%). Individual neutral sugars (rhamnose, arabinose, xylose, mannose, galactose, and glucose) and uronic acid residues present at more than 1% generally had good RSDR values (3.3-22.8%), whereas, as expected for Klason lignin, only the wheat bran sample with a high content (16%) had an excellent RSDR value (5.0%). The gas chromatographic-colorimetric-gravimetric method (Uppsala method) for determination of total dietary fiber (as neutral sugar residues, uronic acid residues, and Klason lignin) has been adopted first action by AOAC INTERNATIONAL.
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The ability of the ruminal anaerobic phycomycete Neocallimastix patriciarum to digest model lignin compounds and lignified structures in plant material was studied in batch culture. The fungus did not degrade or transform model lignin compounds that were representative of the predominant intermonomer linkages in lignin, nor did it solubilize acid detergent lignin that had been isolated from spear grass. In a stem fraction of sorghum, 33.6% of lignin was apparently solubilized by the fungus. Solubilization of ester- and either-linked phenolics accounted for 9.2% of the lignin released. The amounts of free phenolic acids detected in culture fluid were equivalent to the apparent loss of ester-linked phenolics from the sorghum substrate. However, the fungus was unable to cleave the ether bond in hydroxycinnamic acid bridges that cross-link lignin and polysaccharide. It is suggested that the majority of the solubilized lignin fraction was a lignin carbohydrate complex containing ether-linked hydroxycinnamic acids. The lignin carbohydrate complex was probably solubilized through dissolution of xylan in the lignin-xylan matrix rather than by lignin depolymerization.
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A second collaborative study on acid-detergent fiber and lignin has been completed involving 10 laboratories and 6 samples including timothy, alfalfa, soybean meal, barley straw, orchardgrass, and wheat straw. Results from 7 laboratories appeared normal according to the Youden collaborative test and yielded a mean duplicate error of 0.40±0.31, a standard error between laboratories of 0.40, and a coefficient of variation of 1.02%. The duplicate error for lignin was 0.23±0.31, the standard error between laboratories, 0.28, and the coefficient of variation, 4.26%. Results indicate problems with filtering, handling fritted glass crucibles in a uniform weighing procedure, and reliably preparing asbestos used in the preparation of lignin. Modifications of the previously published method include reduction of sample size to 1 g, elimination of the use of decalin, rigorous definition of filtration and weighing procedures, use of P2O5 or Mg(ClO4)2 as desiccant, and determination of a lignin blank. Problems in filtration can be overcome by not using more vacuum than is necessary, making all additions with vacuum off, and allowing 15–30 sec settling before applying suction. The modified acid-detergent fiber and lignin method has been adopted as official first action.
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Aromatic amine-N-xylosides were found to produce both melanoidins and red pigments in methanol solution acidified with hydrogen chloride at 25°. From N-d-xylosyl-p-aminobenzoic acid, 1-p-carboxyphenylimino-5-p-carboxyphenylamino-2-hydroxypenta-2,4-diene hydrochloride, and from N-d-xylosylaniline, 1-phenylimino-5-phenylamino-2-hydroxypenta-2,4-diene hydrochloride were isolated and identified respectively. And further, furfural formed from N-d-xylosyl-PABA or N-d-xylosylaniline under the same condition was identified as 2,4-dinitrophenyl-hydrazone of which anti-form and syn-form were clearly separated by adsorption chromatography with alumina.
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The capacity of cetyl trimethylammonium bromide to dissolve proteins in acid solution has been utilized in development of a method, called acid-detergent fiber method (ADF), which is not only a fiber determination in itself but also the major preparatory step in the determination of lignin. The entire procedure for determining fiber and lignin is considerably more rapid than presently published methods. Compositional studies show ADF to consist chiefly of lignin and polysaccharides. Correlations with the new fiber method and digestibility of 18 forages (r = —0.79) showed it to be somewhat superior to crude fiber (r = —0.73) in estimating nutritive value. The correlation of the new lignin method and digestibility was —0.90 when grass and legume species were separated.
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Heat-drying of forages at temperatures above 50°C shows analytically significant increases in yield of lignin and fiber. The increased yield of acid-detergent fiber (ADF) can be accounted for largely by the production of artifact lignin via the non-enzymic browning reaction. Values for ADF and lignin in dried forages can be corrected on the basis of the nitrogen content of the ADF. The nitrogen content of the ADF is suggested as a sensitive assay for nonenzymic browning due to overheating of feeds.
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Results from sheep digestibility trials, performed at the Danish Institute of Agricultural Sciences in the period from 1984 until now, were analysed according to the Lucas principle. The Lucas principle means that across feeds, apparent digestibilities of nutrients in cell contents can be ascribed to a constant true digestibility and to an endogenous loss, which is a constant proportion of feed dry matter (DM). Based on mean digestibilities for 493 feed samples, a true Neutral Detergent Solubles (NDS) digestibility of 101.3% and an endogenous loss of 90.2 g NDS per kg ingested DM were estimated.
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Synthetic proteins composed of lysine (polylysine, PL) and a random co-polymer of lysine and tyrosine (polylysine/tyrosine, PLT) were incorporated into lignin-like dehydrogenation polymers (DHPs) formed by the peroxidase-catalysed polymerisation of coniferyl alcohol. The yield of water-insoluble DHPs was greater in the presence of the tyrosine-containing PLT than PL. Indeed, the increase in total yield with PLT was often greater than could be accounted for if all the protein added had become incorporated into the DHPs. A comparison of the Fourier transform infra-red spectra of the DHPs formed in the absence and presence of synthetic proteins provided evidence that the presence of PLT had enhanced the incorporation of coniferyl alcohol, albeit in a less cross-linked form, into DHPs. The insolubilisation of PL and PLT was suggested by the presence of absorption bands in the infra-red spectra of their respective DHPs that are characteristic of protein/amide moieties. The insolubilisation of PLT was confirmed by the release of material from PLT-DHPs by digestion with trypsin. Therefore, this study provides evidence that the presence of tyrosine residues may enhance the cross-linking of proteins into lignin.
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Forage fiber digestion followed first- order reaction kinetics even though in- dividual forages differed widely in ma- turity, composition, and rate of fiber digestion. Linearity of individual semilog plots of remaining digestible cell walls on time and their individually high r z (mean ,978) for each of 112 different samples representing 15 species support this general model. Cell wall digestion rates were more highly correlated with soluble dry matter percentage (y = --.0299 -b .00261X, r =.72, P < .001) than with )ignin percentage (r = --.47, P < .001), lignin-to-cellulose (r = --.18), log lignin-to-cellulose ratio (r = --.26, P < .01), or 72 hr in vitro cell wall indigestibility (r = --.38, P < .001). Similarity of mean lignin-to-cellu- lose ratios in theoretically indigestible residues from legumes (1.09) and grasses (.94) suggests a similar role of lignin in limiting extent of digestion. Lignin in dry matter, lignin:cellulose, or log lignin:cel- lulose seem to be equally suitable pre- dictors of cell wall indigestibility in vitro. Legumes were higher in percentage soluble dry matter and lignin and lower in percentage hemicellulose than grasses. Legume cell walls were also more ligni- fied and less digestible, but digested faster than grass cell walls.
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Wheat straw fractionation by ethanol organosolv was studied as pretreatment for enzymatic cellulose hydrolysis. A parametric study focusing on temperature, reaction time, acid catalyst dose, solvent concentration, and particle size was performed to determine their influence on delignification, xylan hydrolysis, and enzymatic cellulose digestibility. Major process parameters were found to be temperature, ethanol concentration, and acid dose. Optimisation of the process towards enzymatic digestibility resulted in a maximum glucose yield of 86% without the use of a catalyst (lignin yield 84%, organosolv at 210°C, 50% w/w aqueous EtOH). Using 30mM H(2)SO(4) as catalyst resulted in similar glucose and lignin yields at a lower temperature (190°C, 60% w/w aqueous EtOH). Lowering the pretreatment temperature by using an acid catalyst substantially improved the yield of the hemicellulose derivatives xylose and furfural. A systematic approach in pretreatment optimisation is vital for development of efficient lignocellulosic biorefineries.
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Examination of humin residues obtained at various stages during lignin determination and of the alcohol-soluble fraction of pre-treated food materials has indicated the necessity for modifying the procedures used in lignin determination. Factors affecting the dispersion and hydrolysis of cellulose are reported, and it is shown that in order to determine as lignin only material insoluble in concentrated acid it is necessary to filter without dilution after the main treatment. A method for determining ‘acid-insoluble lignin’ is proposed and shown to give satisfactory agreement between replicates.
Article
In several tropical forage species the neutral detergent extraction used to determine cell wall and cell contents fractions solubilised a substantial UV‐absorbing polymeric fraction which appeared to be a soluble lignin–carbohydrate complex. A crude product was isolated from spear grass ( Heteropogon contortus ) with a yield of 30 g kg ⁻¹ . In other forages an acetyl bromide method was used to estimate lignin extractable by neutral detergent. For eight species of tropical grasses this gave the following values: Aristida calcyna , 38; Mitchell grass ( Astrebla squarrosa ), 37; Chloris gayana , 31; Eragrostis sp, 37; spear grass, 49; Iseilema membranaceum , 35; Panicum maximum , 36; Sorghum sp, 42; Themeda triandra , 79 g kg ⁻¹ . The levels in two legumes were: Alysicarpus bupleurifolius , 29; Macroptilium atropurpureum , 27 g kg ⁻¹ dry matter. Sequential extractions on spear grass and Mitchell grass showed that most of the 50% dioxan‐soluble fraction was also soluble in neutral detergent, raising the possibility that ‘dioxan lignin’, on which studies of forage lignin structure in other species have been conducted, would be found in the cell contents fraction rather than in the fibre fractions on which lignin analyses have been performed. Addition of dioxan extractives reduced the in vitro neutral detergent fibre (NDF) digestibility of spear grass and Mitchell grass. © 2002 Society of Chemical Industry
Article
Chemical and biological delignification methods were used to investigate the relationship between the concentration and composition of lignin and degradation of forage cell walls. Stem material from lucerne (Medicago sativa L), smooth bromegrass (Bromus inermis Leyss) and maize (Zea mays L) stalks was treated with alkaline hydrogen peroxide, potassium permanganate, sodium chlorite, sodium hydroxide, nitrobenzene, and the lignolytic fungus Phanerochaete chrysosporium. Klason lignin and esterified and etherified phenolic acids were delermined. Cell wall neutral sugar and uronic acid composition and the extent of in-vitro degradability were measured. Chemical delignification generally removed lignin. but the fungal treatment resulted in the removal of more polysaccharide than lignin. The concentrations of esterfied and etherified p-coumaric and ferulic acids were generally reduced in treated cell walls; chlorite treatment preferentially removing p-coumaric acid whereas nitrobenzene treatment removed more ferulic acid. Syringyl moieties were completely removed from the core lignin polymer by nitrobenzene treatment of forage stems. Alkaline hydrogen peroxide and nitrobenzene were generally the most effective delignification treatments for improving polysaccharide degradability, with the grass species responding similarly to delignification whereas lucerne was somewhat less responsive. Fungal delignification, under these experimental conditions, did not improve cell wall degradability of these forages. Multiple regression and covariate analyses indicated that the lignin components measured were not powerful predictors of cell wall degradability. Neither the concentration nor the composition of the lignin fractions was consistently correlated with degradation. This lack of effect was attributed to the more generalised disruption of the cell wall matrix structure by delignification treatments.
Article
The detergent system of analysis partitions lignin into two fractions: acid detergent lignin (ADL), usually equated with forage lignin, and ‘acid detergent dispersible lignin’ (ADDL), the existence of which has scarcely been recognized, but can be higher than ADL in tropical grasses. For nine species ADL and ADDL as percentage of original dry matter were, respectively: Aristides calcyna. 8.9 and 9.8; Astrebla squarrosa, 8.6 and 14.7; Chloris gayana, 3.9 and 6.7; Eragrostis sp, 4.3 and 8.8; Heteropogon eontorius, 3.9 and 10.4; Iseilema membranaceum 7.2 and 8.2; Panicum maximum, 1.8 and 5.7; Themeda triandra, 7.3 and 8.2; Sorghum sp, 3.4 and 13.8. Tropical legumes (four species) had much lower levels of ADDL. Azo-stained fibre showed that most of the free phenolic functions and the alkali-soluble lignin were in the ADDL fraction. The difference between grasses and legumes was so marked that azo-staining may provide a method for distinguishing grass and legume particles in feed or faecal samples. The apparent discrepancies between grasses and legumes in the effect of lignin on digestibility may be explained by the grass lignin having been grossly underestimated as ADL. When Heteropogon contortus and Astrebla squarrosa were incubated in dacron bags in the rumen the ratio of ADDL to ADL in the residual fibre decreased markedly in the first 48 h, indicating a higher apparent digestibility for ADDL. From feeding experiments with sheep the apparent digestibility of ADL and ADDL were 18 and 38% for Astrebia squarrosa and 14 and 26% for Stylosanthes hamata. As isolated lignin corresponding to ADDL was inhibitory in vitro to a mixed rumen microbial population at a concentration of 0.12 mg ml−1. Measurement of ADDL could easily be included in fibre analysis by the sequential detergent method as it would require only UV absorbance measurement on the acid detergent filtrate. This would allow measurement of total lignin within the existing system.
Article
Total dietary fiber (TDF) was measured in 16 foods by three methods: a rapid enzyme-NDF (neutral detergent fiber) procedure supplemented with a separate procedure for soluble (SOL) fiber, the AOAC TDF method and the comprehensive Englyst's procedure. The NDF+SOL method needed less operator time than the AOAC method and its TDF values were in agreement with the AOAC method (y = 0.98 -0.39; r = 0.997) and with the Englyst's method (y = 1.17 -0.19; r = 0.996). The constituent sugars of polysaccharides in NDF+SOL residues were similar to those by the Englyst's method, indicating an adequate estimation of dietary fiber in foods and food products.
Article
Two methods—Klason lignin (KL) and acid detergent lignin (ADL)— for determining lignin concentration in plants were compared using stem material from lucerne (Medicago sativa L), cocksfoot (Dactylis glomerata L) and switchgrass (Panicum virgatum L), at three stages of maturity, and leaf samples from lucerne and cocksfoot. For all forages, KL values were higher than ADL values. Lucerne samples, which had crude protein levels twice that of the grass species, had KL values that were only 30–40% higher than ADL values; in grasses, KL values were 200–300% greater than ADL values. The addition of nitrogenous materials (bovine serum albumin, lysine, and ammonium sulfate) to commercial xylan and cellulose did not result in additional KL residue. Pyrolysis-GC-MS revealed that both residues appeared to be similar to the orginal plant lignin and did not appear to be contaminated with carbohydrate or protein. The higher values for grass KL residues were not due to protein con- tamination or incomplete hydrolysis of carbohydrates, but were more likely due to the solubilization of lignin components by the ADL treatment. KL values may give a more accurate quantification of the total lignin within forage plants.
Article
Two methods - - Klason lignin (KL) and acid detergent lignin (ADL) - - for determining lignin concentration in plants were compared using stem material from lucerne (Medicago sativa L), cocksfoot (Dactylis glomerata L) and switchgrass (Panicum virgatum L), at three stages of maturity, and leaf samples from lucerne and cocksfoot. For all forages, KL values were higher than ADL values. Lucerne samples, which had crude protein levels twice that of the grass species, had KL values that were only 30-40% higher than ADL values; in grasses, KL values were 200-300% greater than ADL values. The addition of nitrogenous materials (bovine serum albumin, lysine, and ammonium sulfate) to commercial xylan and cellulose did not result in additional KL residue. Pyrolysis-GC-MS revealed that both residues appeared to be similar to the orginal plant lignin and did not appear to be contaminated with carbohydrate or protein. The higher values for grass KL residues were not due to protein contamination or incomplete hydrolysis of carbohydrates, but were more likely due to the solubilization of lignin components by the ADL treatment. KL values may give a more accurate quantification of the total lignin within forage plants.
Article
In-vitro experiments have indicated that the soluble lignin-carbohydrate complex (LCC) produced in the bovine rumen is not significantly affected by further digestion in the rumen after passing into solution. The LCC has been shown to precipitate at the low pH of the abomasum and is present in the solid fraction of the faeces. It is concluded that digestion of the LCC is not likely to be significant after it passes from the rumen.
Article
The cell-free rumen liquor of a steer on a diet of spear grass has been shown to contain macromolecular substances in which carbohydrates and lignin-derived compounds are covalently bound to each other. The lignin-carbohydrate complexes are soluble at pH 7 or higher, but precipitate at pH 3. At the latter pH, small amounts of a polymer, assumed to be glycoprotein, remain in solution. Some of the lignin-carbohydrate linkages are broken by treatment with alkali. Treatment with 50mM sulphuric acid for a few minutes at room temperature converts part of the complex into an acetone-soluble product, which still contains both carbohydrate and lignin-derived compounds. The formation of soluble lignin-carbohydrate complexes by the action of rumen micro-organisms on the grass may account for the dissolution (and hence the apparent digestion) of about half of the total lignin-intake.
Article
The acid detergent lignin and Klason lignin methods were compared for their correlation with forage digestibility. Thirty-six forages, including C3 legumes and C3 and C4 grasses, were analyzed for sulfuric acid detergent lignin, Klason lignin, and in vitro digestibilities of dry matter (DM) and neutral detergent fiber (NDF). Twenty of these forages were also fed to lambs at restricted intake for measurement of DM and NDF digestibilities. Lignin concentrations determined by the two lignin methods were positively correlated, and the Klason lignin value was always greater than the acid detergent lignin concentration. The largest differences were observed for grass forages. Digestibilities of forage DM and NDF were negatively correlated with both lignin methods for the in vitro system and the lamb digestibility trials. The degree of correlation for the two lignin methods with digestibility was generally similar across all forages and within forage classes. Slopes of linear regressions of digestibility on lignin concentration did not differ between legumes and grasses. Although the sulfuric acid detergent lignin and Klason lignin procedures gave very different estimates of forage lignin concentration, they were similarly correlated with digestibility and should yield predictions of forage digestibility that have similar accuracy.
Article
An accurate method for estimation of lignin concentration is important for prediction of the digestible energy content of livestock feeds. The accuracy of lignin concentration estimates based on the Klason lignin and acid detergent lignin methods was compared. Ten diverse forage samples were analyzed for protein, carbohydrates, lipids, organic acids, ash, lignin (by both methods), and gross energy. The accuracy of the two lignin concentration estimates was examined by comparing the measured forage gross energy to a gross energy value calculated from the compositional analysis. Use of the acid detergent lignin estimate in this gross energy calculation accounted for 68-84% of the forage gross energy compared to 85-97% of the gross energy using Klason lignin. These results indicate that while Klason lignin estimates are substantially higher than acid detergent lignin estimates, Klason lignin is the more accurate lignin method and does not overestimate lignin because gross energy recoveries were less than 100%.
Article
Ferulate and diferulates mediate cell wall cross-linking in grasses, but little is known about their cross-coupling reactions with monolignols and their role in lignin formation in primary cell walls. Feruloylated primary walls of maize were artificially lignified and then saponified to release ferulate and diferulates and their cross-products with coniferyl alcohol for analysis by GC-FID, GC-MS, and NMR spectroscopy. Ferulate and 5-5-coupled diferulate had a greater propensity than 8-coupled diferulates to copolymerize with coniferyl alcohol, forming mostly 4-O-beta' and 8-beta' and some 8-O-4' and 8-5' cross-coupled structures. Some 8-beta' structures de-esterified from xylans, but these cross-links were subsequently replaced as 8-coupled diferulates formed stable cross-coupled structures with lignin. Based on the incorporation kinetics of ferulate and diferulates and the predicted growth of lignin, cross-products formed at the onset of lignification acted as nucleation sites for lignin polymerization.
Aussprache (Discussion) Die Verfahren der Holzzellstoff-Fabrikation
  • J P Klason
Klason JP (1908) Aussprache (Discussion) Die Verfahren der Holzzellstoff-Fabrikation. In Hauptversammlung Verein der Zellstoff-und Papier-Chemiker, November 23 and 24, at Papierhaus zu Berlin, pp. 52-3.
The Ruminant Nutrition System
  • L O Tedeschi
  • D G Fox
Tedeschi LO, Fox DG (2016) The Ruminant Nutrition System. Acton, MA : XanEdu Publishing, Inc.
Physical, chemical and kinetic factors associated with fiber digestibility in ruminants and models describing these relationships
  • E Raffrenato
Raffrenato, E (2011) Physical, chemical and kinetic factors associated with fiber digestibility in ruminants and models describing these relationships. PhD Thesis, Cornell University, Ithaca NY.
Factors affecting gravimetric determination of lignin by the 72% H 2 SO 4 method
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  • R M Seborg
  • R L Mitchell
Ritter GJ, Seborg RM, Mitchell RL (1932) Factors affecting gravimetric determination of lignin by the 72% H 2 SO 4 method. Ind Eng Chem Anal Ed 4, 202-204.
The Detergent System for Analysis of Foods and Feeds
  • P J Van Soest
Van Soest PJ (2015) The Detergent System for Analysis of Foods and Feeds; ISBN: 978-1-63095-134-4. Ithaca, NY: Cornell University.