Digestion of polysaccharide constituents of tropical pasture herbage in the bovine rumen : Part III. Examination of the celluloses and hemicelluloses of spear grass ( heteropogon contortus) which resist digestion

Abstract

The hemicellulose and cellulose components of spear grass which survive digestion in cattle have been examined by isolation of these polysaccharide fractions from the following samples: ( i) fresh spear grass, ( ii) spear grass held in the rumen for 3 days, ( iii) a mixed pasture sample (predominantly spear grass), ( iv) faeces fibre from cattle fed on ( iii). The digested samples showed lower contents of cellulose and higher contents of hemicellulose than the undigested samples. The hemicellulose-B components from each were further separated into linear and branched fractions and compared. In all cases, the branched hemicellulose contained more arabinose and uronic acid than the corresponding linear hemicellulose. The arabinose content of the samples of undigested hemicellulose-B was higher than that in the digested samples.