Fermentation pattern and changes in cell wall constituents of straw-forage silages, straws and partners during storage

Abstract

Three types of wheat straws, i.e. untreated, sodium hydroxide treated and steamed, were ensiled each in combination with sugar beet leaves and tops (SBLT) in a ratio of 1:3, SBLT and lucerne in a ratio of 1:1.5:1.5, lucerne in a ratio of 1:3 and lucerne in a ratio of 1:3 plus 2% molasses in laboratory glass silos to study the effect of pretreatment and ensiling of untreated and treated straws with other forages on fermentation pattern and changes in cell wall constituents of silages. Thus in all there were 12 treatment combinations with 12 replications each and they were unloaded in triplicate at 10, 35, 60 and 90 days of ensiling. Pooled results such as untreated straw silages (S 1), alkali treated straw silages (S 2) and steamed straw silages (S 3) have been presented. The straws and partners were also separated from freeze dried mixtures to study the changes in cell wall constituents. The alkali treatment of straw decreased neutral detergent fibre (NDF) and hemicellulose and increased the cell contents (CC), pH, buffering capacity (BC) and in vitro digestibility of organic matter (IVDOM). Steam treatment increased the IVDOM to 17 units. All the silages had a very good texture and pleasant smell. Major quantities of water soluble carbohydrates (WSC) were utilized during the first 10 days in all of the treatments. The silages in treatments S 1 and S 3 were of very good quality. In spite of higher pH (4.71), the quality of silages made with alkali treated straw (treatment S 2) was also good. All the silages were aerobically stable at 60 and 90 days of unloading. The losses of dry matter (DM) and digestible organic matter (DOM) increased with increasing storage period and the values were slightly higher for treatment S 2. More acids were produced than the WSC utilized during fermentation. Considerable quantities of hemicellulose and some lignin disappeared during ensiling in all the treatments and thus affected the composition of cell wall constituents. There was an increase in hemicellulose disappearance with increasing fermentation intensity. The absorption of soluble constituents by straw doubled its CC and crude protein (CP) values and also increased the IVDOM values with a corresponding decrease in the partners and the increase was more for untreated straw. Absolute recovery of DOM was more than the DM absorbed by the straw from the partners. An overall improvement of 12.10, 7.95 and 8.30% in DOM was observed for untreated, alkali treated and steamed straws, respectively.