Effects of maceration of rice straw on voluntary intake and performance of growing beef cattle fed rice straw-based rations

Effects of field scale maceration on voluntary intake of rice straw, diet digestibility of neutral detergent fiber (aNDF) and performance of growing cattle were evaluated through chemical, in vitro and animal feeding experiments over a 3-year period. Due to the sequential nature of the study (i.e., a discrete experiment was completed in each year), the method of maceration differed among years. However. in each year. replicated rice fields of approximately 2.4 ha each, which had been managed similarly during growth, were harvested with or without maceration immediately after harvest. While no quantitative measure of maceration was applied in any experiment, the extent of maceration in year I was visually judged to be very light, characterized by only a few stem punctures and no longitudinal stem shredding. In year 2. the extent of stem puncture was increased, most internodes were crushed and a small amount of longitudinal shredding had occurred and, in year 3, the amount of internode crushing and longitudinal shredding was extreme. In each feeding experiment, cattle were managed in groups of 8-10 and fed the experimental diets for a 14-day adaptation period prior to weighing on day 0 of the study. Diets consisted of alfalfa hay, concentrate ingredients and rice straw that were fed for ad libitum intake. In general. the chemical composition of the rice straw was typical of California rice straw and, in spite of some differences due to maceration within year, there was no consistent impact on any analyte among years. In each year, the macerated rice straw had a numerically higher calculated metabolizable energy value, but these differences failed to reach statistical significance.