Growing Performance and Metabolism of Steers Fed Increasing Inclusions of Condensed Distillers Solubles in Forage-Based Diets

Two experiments were conducted to: 1) determine the energy value of corn condensed distillers solubles (CDS) and wet distillers grains plus solubles (WDGS) in beef cattle growing diets; and 2) determine the effect of CDS on diet digestibility and rumen fermentation parameters in forage-based diets. In Exp. 1, 120 crossbred steers (initial BW = 366 ± 30 kg) were utilized in a generalized randomized complete block designed study analyzed using mixed procedure of SAS. Steers were individually fed increasing inclusions of CDS or WDGS at 0, 10, 20, 30, or 40% of the diet displacing corn for 96 d. The basal diet (0% CDS or WDGS) contained 50% grass hay, 40% dry-rolled corn, 5% supplement, 3% treated soybean meal, and 2% corn gluten meal. A quadratic response was observed for intake (P = 0.02) and G:F (P = 0.02) of steers fed increasing inclusion of CDS. Feeding CDS resulted in an 11, 16, 13, and 11% decline in G:F compared to corn for the 10, 20, 30, and 40% inclusions of CDS, respectively. Steers fed WDGS linearly increased DMI (P < 0.01) and ADG (P = 0.05) with no change in G:F as inclusion increased. In Exp. 2, 6 ruminally cannulated steers (BW = 404 ± 34 kg) were utilized in a 6 x 6 Latin square to determine the effects of CDS in a forage-based diet on diet digestibility and rumen fermentation parameters. Data were analyzed using the glimmix procedure of SAS. Steers were fed CDS at 0, 10, 20, 30, or 40% of the diet displacing corn, and an all grass hay control. Intakes linearly decreased (P = 0.01) for DM, OM, and NDF with increasing inclusions of CDS. Total tract digestibility of DM and OM was not different among CDS inclusions; whereas, NDF digestibility (P < 0.01) linearly declined with increasing CDS inclusions. Surprisingly, dietary DE (Mcal / kg) linearly increased (P < 0.01) with inclusions of CDS. Molar concentrations of acetate linearly decreased (P < 0.01) with linear increases in propionate (P = 0.01) and butyrate (P < 0.01) as CDS inclusion increased. De-oiled CDS appear to decrease total tract digestibility of NDF compared to corn in forage-based diets. A 73.7% TDN value was estimated for CDS fed at 40% of the diet compared to corn, suggesting CDS has less energy than corn in forage-based diets.