Effect of Delignification on In Vitro Digestion of Alfalfa Cellulose

Abstract

Alfalfa forages containing low or high content of cell walls were ground in a Wiley mill through 1- or 8-mm screens. Portions of the forages were delignified with permanganate. Delignified and intact alfalfas were digested in vitro to ascertain rate and extent of digestion of cell wall and cellulose. Initial and residual cell wall and cellulose were greater for intact high cell wall and 8-mm alfalfa than for low cell wall and 1-mm alfalfa whereas potentially digestible (initial minus undigestible) cell wall and cellulose did not differ. Cellulose content of delignified forages was considerably greater than that of intact forages. Cell wall of low cell wall digested slightly faster (.0550/h) than high cell wall (.0485/h), and 8-mm forage had a slightly higher rate of digestion (.0505/h) of cell wall than 1-mm (.0485/h). Within intact or delignified alfalfas, cellulose digested similarly for either cell wall amount or particle size. Cellulose of delignified forages had a longer digestion lag (23 h) than intact forages (4.5 to 6.0 h), but once cellulose digestion began, it was much more rapid for the delignified forages (.161/h) than for intact (.048/h). Delignification greatly increased both rate and extent of digestion of cellulose in alfalfa. © 1983, American Dairy Science Association. All rights reserved.