In Vitro Methane Production and in Sacco Degradability of Processed Wheat and Rice Straws

The present study was undertaken to assess the in vitro methane production and in sacco degradability of naturally fermented wheat and rice straw with urea for 9 days in a 2 × 2 factorial design. The natural fermentation of wheat and rice straw with urea increased the crude protein content by 48.6 and 46.3% while hemicellulose content decreased by 20.2 and 15.3%, respectively, without affecting the lignin content. In vitro studies revealed that irrespective of processing, the low NGP in rice straw could be due to low degradability of NDF (P<0.05) and that of true OM (P<0.01). The methane produced by rice straw at t½ was higher (P<0.01) than that produced by wheat straw (1.55 vs. 1.45 ml/mg digestible OM). The availability of ME from fermented wheat straw was higher (P<0.01) than that of fermented rice straw. The NGP, digestibility of nutrients and ME availability were higher (P<0.01) in fermented straws as compared to unfermented straws. The methane production estimated at t½ was low (P<0.05) in fermented straws as compared to their unfermented counterparts (1.76 vs. 1.24 ml/mg digestible OM). Irrespective of type of straw. The production of TVFA's, acetate, propionate and that of butyrate were higher (P<0.01) in naturally fermented straw preparations as compared to that of unfermented straws. The digestion kinetic parameters for DM and NDF assessed by in sacco technique revealed that irrespective of the straw, the natural fermentation increased (P<0.01) rapidly soluble fraction, insoluble but potentially degradable fraction and effective degradability as compared to unfermented straws. The rumen fill values for DM were comparable in straw species, but that for NDF were lower in wheat straw than rice straw as well as in unfermented than fermented straws. Wheat straw as compared to rice straw had lower methane production potential and that natural fermentation of straws with urea not only depressed in vitro methane production but also improved the quality and nutritional worth of straws.