Date of this Version
Published in Crop Sci. 55:681–687 (2015).
Grain sorghum [Sorghum bicolor (L.) Moench] is an important crop for rainfed production systems with 2.7 million ha grown in the United States in 2013. The brown-midrib (bmr) mutations, especially bmr-12, have resulted in low stover lignin and high fiber digestibility without reducing grain yield in some sorghum lines. However, the effect of the bmr trait on beef cattle (Bos taurus) performance when grazing crop residue is unknown. Our objectives were to validate previous small-plot results reporting no grain yield difference between near-isogenic bmr-12 (BMR) and wild-type control (CON) A Wheatland × R
Tx430 sorghum hybrids in a field-scale experiment and to determine if BMR stover enhances beef production in a grazing experiment. Four replicated paddocks (2.3 ha) were planted in 2006 and 2008 near Mead, NE. Crossbred yearling steers (240 ± 17 kg hd-1) grazed (2.6 steers ha-1) paddocks following grain harvest for 72 d in 2006 and 61 d in 2008. Forage was sampled 4, 30, and 60 d after grazing began. Grain yield of BMR was 6% less (P = 0.01) than CON with no difference in stover neutral detergent fiber (NDF) content, but BMR stover had higher in vitro NDF digestibility (IVNDFD) (31%; P < 0.0001), steer average daily gain (ADG; 0.18 kg hd-1 d-1; P = 0.001), and body weight (BW) gain (29 kg ha-1; P = 0.002), resulting in an estimated increase in net return of $133.84 ha-1 due to BMR. Results suggest that the A Wheatland × R Tx430 bmr-12 hybrid is an effective dual-purpose sorghum crop for both grain and beef production.