Grain sorghum (GS) has traditionally been grown in south Texas. In the Texas High Plains, interest in forage sorghum (FS) and sorghum x sudangrass (SS) production has increased because of its use as a roughage source in ruminant diets. The objective of this study was to compare forage agronomic traits and nutritive value of FS, SS, and GS that can be grown regionally as a roughage for beef producers. Nine cultivars (FS n=4; SS n=4; and GS n=1) with unique genetic traits were selected and grown. Data was collected on yield, lodging, and height prior to harvest. Forage subsamples were collected, chopped, and analyzed for nutrient content. Additional forage subsamples were collected and packed into mini-silo buckets for approximately 120 days and analyzed for nutritional value. Results from this study demonstrate that plants were taller (P was less than or equal to 0.05) and produced greater (P was less than or equal to 0.05) forage yields in 2012 compared to 2011 due to the greater amount of field water in 2012; average yield in 2011 was 4.0 Mg/ha compared to 8.8 Mg/ha in 2012. Differences in nutritional attributes likely relate to growing condition and plant size/maturity. Protein was less (P less than or equal to 0.05) in 2011 compared to 2012 (8.1 and 11.9%CP, respectively). Fiber was also numerically (NDF; P greater than or equal to 0.05) and statistically (ADF and ADL;P less than or equal to 0.05) less in 2011 compared to 2012. Ensiled samples did not correlate well with greenchop samples (range r2=0.66 to r2=0.11); consequently, greenchop nutritional attributes may not be useful in predicting actual feeding value of an ensiled product. Regional beef and forage producers should evaluate sorghum forage cultivars for agronomic and nutritional attributes that will help them meet their production goals for yield, feeding value, or both.
July 3, 2014
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