Effect of sodium hydroxide treatment of rice straw on cell wall composition and digestibility of dry matter

The conditions of NaOH treatment of rice straw to improve digestibility were investigated by varying the concentrations of NaOH and changing the length of the treatment period. The neutral detergent fiber (NDF) and crude hemicellulose (CH) contents of straw remarkably decreased, as increasing the level of NaOH treatment from 1 to 4%. As the treatment period with NaOH proceeded from 0 to 21 days, the NDF, CH, acid detergent fiber (ADF), crude cellulose, and acid detergent lignin (ADL) contents in straw decreased. Lignin contents determined by the three lignin analytical methods were positively correlated with each other, but acetyl bromide lignin (AcBrL) value was significantly greater than Klason lignin (KL) and ADL values. The lignin contents of straw were reduced by NaOH treatment, and the degree of reduction was dependent on NaOH concentrations. In situ digestibilities of straw dry matter (DM) were negatively correlated with lignin contents. The degree of correlation for lignin values determined by the three methods with digestibility was similar, but AcBrL value was strongly correlated with DM digestibility. The increased in situ DM digestibility of NaOH treated straw suggests that NaOH treatment can effectively improve the nutritive value of rice straw for use as a ruminant feedstuff