Nutritional properties of the leaf and stem of rice straw

Abstract

The proportion of the leaf blade, leaf sheath and stem fractions in six rice straw varieties averaged 30, 40 and 30%, respectively. In vitro dry matter digestibility (IVD) of these fractions, estimated by the cellulase-neutral detergent solution procedure, was 503, 513 and 610 g/kg, respectively. The lower IVD of the blade and sheath was due to lower degradation parameters estimated by a simple technique of incubating samples in a cellulase-buffer solution at 38°C for 3, 6, 12, 24, 48 and 72 h. Treatment with 4% urea solution for 21 days increased the IVD and the degradation characteristics of the leaf fraction more than the stem but treatment with a 4% sodium hydroxide (NaOH) solution for 21 days improved the IVD and degradability characteristics of all straw fractions to the same extent. The leaf had a lower neutral detergent fibre (NDF), higher total and insoluble ash than the stem. Urea treatment which increased total ash but decreased insoluble ash in the leaf were increased in the stem. NaOH treatment increased total and insoluble ash in all fractions. The NDF content, lower in the untreated leaf compared to the stem, was unaffected by but decreased after urea and NaOH treatment, respectively. Crude protein (CP) content, similar between untreated straw fractions, increased after urea but decreased after NaOH treatment .Principal component scores of the leaf and stem fractions derived from a principal component analysis of the analysed variables showed that the leaf ranked higher in nutritive value than the stem before and after chemical treatment. The high leaf content of modern rice straw varieties should therefore promote the utilisation of rice straw as a ruminant feed.