Leaf to Livestock and Stem to Biofuel: Sudangrass and Sorghum-Sudangrass.

If large amounts of the Great Plains are used to grow grass for bio-fuel production, this may have a significant negative impact on beef production because much of this land is used or could be used to grow forage for cattle. However, stems of most forage plants have poor quality and value for cattle, but could be used as feedstock for bio-fuel production. Machinery to separate forage leaf from stem during harvesting is being developed. Therefore, quality of leaf and stem of two highly productive warm-season annual grasses was evaluated to determine if they could fit this strategy. Hayking hybrid sudangrass [Sorghum bicolor ( L.) Moench] and Legend BMR 440 sorghum-sudangrass (Sorghum bicolor-Sorghum bicolor) were grown under irrigation on fine-sandy loam. N and P were applied at seeding at 62.4 and 17.5 kg/ha, respectively. Sudangrass and sorghum-sudangrass were no-till seeded in late July at 28.0 and 33.6 kg/ha, respectively, then harvested at a 9 cm stubble height in late September. Samples were analyzed for neutral and acid detergent fiber (NDF and ADF), acid detergent lignin (ADL) and in vitro dry matter disappearance (IVDMD) with ANKOM equipment and for nitrogen content with a Carlo-Erba analyzer. Cellulose concentration was estimated as ADF minus ADL. Hemicellulose concentration was estimated as NDF minus ADF, and crude protein (CP) concentration was estimated as %N x 6.25. All variables were expressed on a DM basis. Concentrations of fiber-related variables as well as IVDMD and CP were generally indicative of higher forage quality in leaf compared to stem for both forage types (P < 0.01), and leaf forage quality was adequate for most types of beef cattle in many stages of production. For sorghum-sudangrass, leaf and stem were 51 and 49%, respectively, of the whole plant dry matter. For sudangrass, leaf and stem were 46 and 54%, respectively, of the whole plant dry matter. If sorting of leaf and stem can be accomplished inexpensively for these two species, it may be economically feasible to grow them for both cattle forage and bio-fuel feedstock and thus create a win-win situation for cattle and bio-fuel production.