The feeding quality of rice (Oryza sativa L.) straw at different cutting heights and the related stem morphological traits

This study was to investigate the feeding quality of rice (Oryza sativa L.) straw at different cutting heights and the related stem morphological traits. Wuyujing 3, Yangfujing 8 and Liangyoupeijiu in 2010, and Wuyujing 3, Nanjing 44, Nanjing 46, and Liangyoupeijiu in 2011 were used in this study. In 2010, we investigated the feeding quality related traits (such as nonstructural carbohydrates (NSC), crude protein (CP), hemicelluloses and acid detergent fiber (ADF) contents) of rice straw among three cutting heights 10cm, 20cm and 30cm. In 2011, we investigated the nutrient contents (such as NSC, CP, hemicelluloses and ADF contents and in vitro dry matter digestibility (IVDMD)) of leaf, sheath and stem in the top 1st, 2nd and 3rd nodes and the stem morphological characteristics by free hand sections. The results in 2010 indicated that the NSC content of rice straw at 10cm cutting height was higher than that at 20cm and 30cm cutting heights, CP content of rice straw at 10cm cutting height was lower than that at 20cm and 30cm cutting heights, hemicelluloses and ADF contents were not significantly different among 3 cutting heights. The results of 2011 indicated that the NSC content in stem of the top 3rd node was much higher than that in the 2nd and 1st node, and higher than that in leaf and sheath of the same node. CP content in leaf was much higher than that in stem and sheath. Hemicelluloses content in leaf and sheath was higher than that in stem, and ADF content was higher in sheath than that in leaf and stem, but all not significantly (p>0.05). IVDMD of stem was higher than leaf and sheath. Those results could explain the feeding quality differences of rice straw at different cutting heights. Wall thickness (WT) and the parenchyma area percentage of stem were significantly positively correlated with NSC content and IVDMD (p<0.05), which could be used as selection traits for more digestible rice straw.