Effect of sodium hydroxide and alkaline hydrogen peroxide treatment on physical and chemical characteristics and IVOMD of mustard straw

Mustard straw (MS) was soaked for 6 h in the solutions containing 0% (S0), 1% (S1) or 2% (S2) sodium hydroxide (NaOH) and 0% (H0) or 1.5% (H1) hydrogen peroxide (H2O2) following a 3 2 factorial design. The pH of the untreated MS (near neutral) was increased to more than 10 after treatment with NaOH (S1H0 and S2H0) or alkaline hydrogen peroxide (AHP; S1H1 and S2H1). The treatment effect on tenacity was not signi®cant. The NDF and ADF contents of MS increased signi®cantly (p<0.01) in the treatment S0H1, whereas these decreased signi®cantly (p<0.01) in the treatments S2H0 and S2H1. However, the change in NDF and ADF was not signi®cant in S0H0, S1H0 and S1H1 treatments. The content of both NDF and ADF decreased linearly (p<0.01) with increasing level of NaOH in the soaking medium. The effect of various treatments on cellulose content was almost similar to that of NDF and ADF. The acid detergent lignin content of MS increased signi®cantly (p<0.01) in case of S1H0, S0H1and S1H1 but the differences were not signi®cant among UMS, S0H0, S2H0 and S2H1. The IVOMD content of untreated MS was 162 g kgÿ1 DM and it increased signi®cantly (p<0.01) when straw was soaked in S1H0, S2H0, S1H1 and S2H1, whereas it reduced slightly due to either water (S0H0) or H2O2 (S0H1) treatment. With the increasing level of NaOH, the IVOMD improved signi®cantly (p<0.01). It is concluded that the cell wall constituents and IVOMD of MS were modi®ed by NaOH with or without H2O2 in a way that in vitro organic matter digestibility (IVOMD) of treated MS was 82±112% units higher than untreated MS. # 2000 Elsevier Science B.V. All rights reserved.