Exploring synergies between biofuel coproducts for finishing beef cattle

Two experiments were conducted to evaluate the effects of feeding condensed distillers solubles (DS) and crude glycerin alone or in combination on performance of finishing beef cattle and in vitro fermentation. In both experiments, dietary treatments consisted of a steam-flaked corn (SFC) based-diet with 0% DS or crude glycerin (CON), 10% condensed distillers solubles (CDS), 10% crude glycerin (GLY), or a combination of 5% DS and 5% crude glycerin (C+G) included on a DM basis. All treatment diets contained 15% (DM basis) wet distillers grains plus solubles (WDGS). In Exp. 1, crossbred steers (n=250; initial BW = 322 ± 15 kg) were used in a randomized complete block finishing trial. Growth performance and gain efficiency were not different (P > 0.10) across all treatments. Treatment had no effect (P > 0.10) on carcass weight, marbling score, yield grade, LM area, or % grading USDA choice. In Exp. 2, ruminal fluid was collected from 2 ruminally cannulated steers to evaluate in vitro fermentation characteristics. No differences (P = 0.43) were observed for dry matter disappearance (DMD) across all treatments. The GLY and C+G treatments had decreased (P = 0.02 and P = 0.05, respectively) neutral detergent fiber disappearance (NDFD), while the CDS treatment tended to have decreased (P = 0.06) NDFD compared to CON. Concentrations of NH3 decreased (P < 0.04) with GLY and C+G treatments compared to CON. Total gas production decreased (P < 0.01) for the C+G treatment compared to other treatments. Likewise, the C+G treatment also had decreased (P < 0.07) percent of CO2 than other treatments. Percent CH4 decreased (P = 0.01) for the C+G treatment compared to the CON and CDS treatments, but did not differ (P = 0.13) from the GLY treatment. The CDS treatment had increased (P < 0.02) total VFA compared to the CON or C+G treatments. Treatments had no effect (P > 0.17) on concentrations of acetate, propionate, and butyrate, but valerate concentrations were the greatest (P < 0.04) for the CON treatment. Concentrations of isobutyrate increased (P < 0.05) for the CON and C+G treatments compared to the GLY treatment and tended to increase (P < 0.10) compared to the CDS treatment. Including DS or glycerin in the substrates decreased (P < 0.08) isovalerate compared to CON. Feeding additional byproducts such as DS and crude glycerin alone or in combination in a finishing diet did not alter live animal performance or carcass characteristics; however, feeding a combination of the two byproducts may alter in vitro fermentation.