Effects of corn processing method in diets containing sorghum wet distillers grain plus solubles on performance and carcass characteristics of finishing beef cattle and on in vitro fermentation of diets

Two randomized complete block design experiments with a factorial arrangement of treatments were conducted to study the effects of corn processing method and inclusion of sorghum wet distillers grain plus solubles (SWDGS) in beef cattle finishing diets. In Exp. 1, 160 crossbred steers (primarily British x Continental breeding; initial BW = 397.6 +/- 29.4 kg) were fed diets based on dry-rolled (DRC) or steam-flaked corn (SFC), with or without the inclusion of 15% SWDGS (DM basis). Corn processing x SWDGS interactions were not detected (P >= 0.20) for performance and most carcass characteristics. The G: F was less (P < 0.01) with DRC- than with SFC-based diets. Steers fed SFC-based diets had greater 12th-rib fat thickness (P = 0.03), yield grade (P = 0.02), and a smaller LM area (P = 0.08) than steers fed DRC. Inclusion of 15% SWDGS resulted in decreased G: F (P < 0.01) than for diets without SWDGS. In addition, steers fed SWDGS had decreased HCW (P = 0.01) and dressing percent (P = 0.03) than those fed no SWDGS. In Exp. 2, diet samples from Exp. 1 were used to evaluate rate of in vitro gas production, IVDMD, and H2S concentrations in gas. No significant corn processing x SWDGS interactions were noted for any of these measurements or for mathematically fitted gas production parameters, except for the predicted maximum value of gas production. The SFC-based diets had greater IVDMD (P = 0.01), area under the gas production curve (AUC; P = 0.02), and rate (k) of gas production (P = 0.02) than DRC-based diets. Inclusion of 15% SWDGS in the substrates decreased IVDMD (P < 0.01), AUC (P = 0.03), and rate of gas production (P = 0.04) compared with 0% SWDGS. Hydrogen sulfide concentrations in gas did not differ (P > 0.10) with corn processing method or addition of SWDGS. Overall, these data suggest that the response to 15% SWDGS in finishing diets was not affected by corn processing method, but including 15% SWDGS in finishing diets decreased G: F, IVDMD, and gas production AUC values to approximately the same extent as replacing SFC with DRC.