In Situ Disappearance of Cell Wall Monosaccharides in Alkali-Treated Orchardgrass and Alfalfa

The effect of varying levels of alkali treatment on the composition and disappearance of cell wall monosaccharides in alfalfa and orchardgrass was determined. Two field replicates each of first-cutting alfalfa (bud and midbloom) and orchardgrass (prehead and head) were treated at harvest with 0 (no solution applied), 2, 4, 6, or 8g NaOH/100g forage DM. Forages were hand cut, hand sprayed, and sun cured as hay. Disappearance kinetics of cell wall monosaccharides were measured by suspending polyester bags containing the forages in the cow's rumen for 6, 12, 24, 36, 60, and 72h. Alkali treatment resulted in the following effects on forage NDF: decreased galactose content in mature orchardgrass and decreased glucose content of immature alfalfa; increased disappearance of xylose and glucose in all forages except in mature alfalfa; and increased rate of disappearance of xylose in immature orchardgrass and mature alfalfa and of arabinose in immature orchardgrass. Alkali treatment had limited effects on content of cell wall monosaccharides of two maturities of orchardgrass and alfalfa. Excluding mature alfalfa, alkali treatment increased disappearance of cell wall xylose and glucose in all forages.