CHANGES IN THE CELL-WALL COMPONENTS OF LABORATORY SILAGES AND THE EFFECT OF VARIOUS ADDITIVES ON THESE CHANGES

Laboratory silages [ryegrass] were prepared and opened after 2, 20, 60 and 150 days. The silages were made without any additive and with formaldehyde, formic acid, hexanoic acid, benzoic acid or sulfuric acid. The cellulose, hemicellulose, acetyl, alkali-labile phenolic acids and core lignin were determined in all silages as well as the composition of hemicelluloses. In all the silages the core lignin remained unchanged while the cellulose content decreased by up to 5%. Large losses of acetyl residues and alkali-labile phenolic acids were observed in all the silages and losses of 10-20% of the hemicelluloses were found. Losses of hemicellulose were not uniform. The arabinose side chains were preferentially cleaved relative to the xylose residues. Part of the loss of carbohydrate could have been caused by acidic conditions in the silage as well as by microbial activity. Silages made using acidic additives with the highest pKa values lost the greatest proportion of carbohydrate. The implications of these results on rumen activity are discussed; the ruminant animal is capable of using the fibrous portion of the plant material as a source of energy.