Lignin and Methoxyl Groups as Related to the Decreased Digestibility of Mature Forages

Fiber Composition and in Vitro Digestibility of Corn Stover Fractions in Response to Ammonia Treatment

“…Quinone methide regeneration from lignocellulose during ruminal digestion would result in repolymerization of lignin structures or copolymerization with polysaccharides or other digesta components. The interrelationship between extent of quinone methide regeneration with lignin S/G ratio, or lignin methoxyl content (Glasser and Kelley, 1987), provides an explanation for the reported negative correlation between S/G ratio (Buxton and Russell, 1988;Reeves, 1985) and lignin methoxyl content (Quicke and Bentley, 1959;Sewalt et al, 1993) and digestibility.…”

“…Furthermore, the lignin monomeric composition (i.e., syringyl/guaiacyl ratio (S/G ratio) or, alternatively, methoxyl content) affects the formation of intra-and intermolecular linkages via quinone methides during lignification and lignin aging (Leary, 1980). The reported negative correlation of S/G ratio (Buxton and Russell, 1988;Reeves, 1985) and methoxyl content (Quicke and Bentley, 1959;Sewalt et al, 1993) with forage digestibility may be explained by the higher likelihood of quinone methide formation and regeneration from syringyl lignin than from guaiacyl lignin (Glasser and Kelley, 1987).…”

Seasonal and Growth Period Changes of Some Nutritive Components of Kikuyu Grass

“…Crude Protein and Lignin.-As indicated in Table 1, the fibrous components of kikuyu grass as represented by crude fiber, detergent fiber, cellulose, hemicellulose and holocellulose were affected by period of regrowth and seasons. As shown in Table 2 Many workers have demonstrated that lignin, crude fiber or cellulose increase and crude protein decrease as plants mature (Patton, 1943;Kamstra et al, 1958;Quicke and Bentley, 1959). These and other authors suggest increase in lignin as a cause for decreasing plant digestibility with approaching maturity.…”

Lignin Impact on Fiber Degradation: Increased Enzymatic Digestibility of Genetically Engineered Tobacco (Nicotiana tabacum) Stems Reduced in Lignin Content

“…The inhibitory effects of lignin depend on its monomer composition (Reeves, 1985;Buxton and Russell, 1988;Sewalt et al, 1996a) , functional groups (Sewalt et al, 1996b(Sewalt et al, , 1997a, and the extent of cross-linking to wall polysaccharides. The ratio of indigestible residue to lignin content has been reported to increase with maturity [e.g., Quicke and Bentley (1959), Grabber et al (1992)], which may be caused by a different type of lignin (with respect to monomer composition) being deposited in the cell wall at a later stage of maturity. Increased lignification with advancing maturity depresses digestibility of grasses more than of legumes, which is associated with a more rapid increase in syringyl-rich lignin in grasses (Buxton and Russell, 1988).…”