Evaluating Sorghum x Sudangrass Seed Digestibility

Summary with Implications A sorghum-sudangrass hybrid was swathed in the hard dough stage and grazed by growing steers from November 2023 to January 2024. Steers appeared to select the seedheads when grazing. The seed made up approximately 12.6% of swathed forage mass, but its energy contribution appears limited due to poor digestibility. When incubated whole, only 23% of dry matter and 13% of starch was digestible. Grinding improved digestibility but still left 40% of the dry matter and over 85% of starch unavailable. Weathering over two months did not improve digestibility, indicating the seed coat remains intact through winter. Compared to sorghum grain, the hybrid seed had significantly lower starch digestibility. Because cattle are unlikely to sufficiently chew the small seeds to break the tough seed coat, the actual energy benefit is minimal. Although seedheads are readily consumed, producers should not assume they contribute significant nutritional value in grazed systems.