Digestibility of Forage Hemicellulose and Pectin by Rumen Bacteria in Vitro and the Effect of Lignification Thereon

Open Access
Publisher Website
Google Scholar
Abstract
The rate and extent of hemicellulose fermentation by rumen bacteria in vitro was investigated with 4 maturity stages of timothy, 3 of alfalfa and 2 of orchard grass. With all forages, the rate and extent of hemicellulose fermentation decreased as the plant matured. When the forage particle size was reduced by ball-milling, an attempt to remove any barrier type inhibition by lignin, both the rate and extent of hemicellulose fermentation were increased. Similar results were obtained when pectin fermentation was investigated with the 3 maturity stages of alfalfa. The experimental results suggest that the decreased digestibility of hemicellulose and pectin in the mature forage is a result of lignin forming a physical barrier between the plant hemicellulose and pectin and the rumen bacteria. It was of interest that the present results on rate and extent of fermentation as well as the effect of ball-milling are identical to those obtained previously on forage cellulose digestion (J. Dairy Sci., 44:2242. 1961).