Adjustment of pH and enzymatic treatment of barley straw by dry processing method

Abstract

Chemical characteristics and ruminal degradability of barley straw when treated with dry application (spraying technique) of acid and alkali were studied over the adjusted pH range (1.5–12.5 by measuring titratable capacity). Enzymatic (a cellulase product) effectiveness was also examined on pretreated straw at pH 3.5, 4.5 and 11.5. Treated straws were then ensiled for four weeks. Results showed that the solubility of dry matter (DM) and hemicellulose (HC) was altered quadratically within the pH region, while that of cellulose (CL) and lignin displayed minor changes. Release of phenolic compounds and water-soluble carbohydrates increased linearly with increasing alkaline pH whereas, they were raised from pH 7 up to pH 2 and then decreased at pH 1.5. DM degradability was little affected under acidic conditions and the highest value was achieved at pH 2, whereas fibre components (HC and CL) degradability was orderly reduced towards zero with decreasing pH. Increasing pH with application of alkali led to a linear enhancement of DM, HC and CL degradability. An interaction between pH level and enzymatic treatment was detected, such that the degradability of pretreated straw at pH 4.5 was enhanced but no improvement was attained at pH 3.5 and 11.5 with enzyme addition. Dry processing of barley straw under acidic pH, increased fibre solubilisation, reduced ruminal fibre degradability and exhibited a positive effect on the efficacy of the exogenous enzyme, while alkaline pH, in particular pH 12, substantially improved the degradation of barley straw.