Evaluation Of Whole Corn Substitution In Diets Based On Steam-Flaked Corn Containing Different Concentrations Of Wet Distillers Grains With Solubles For Beef Cattle

Objective: Our objective was to determine effects of substituting steam-flaked corn (SFC) with whole shelled corn (WSC) in finishing diets containing wet distillers grains with solubles (WDGS) on cattle performance, carcass characteristics, digestion, and rumen microbial ecology.Materials and Methods: The study used 642 Angus cross heifers (411.7 +/- 18.0 kg of initial BW) assigned to 36 pens. Treatments (2 x 3 factorial) were 6 SFC-based finishing diets with 0 or 20% WSC and 0, 15, or 30% WDGS (DM basis). Ruminal fluid was collected to evaluate ruminal characteristics, and feces and manure were collected to determine nutrient digestion and losses.Results and Discussion: Heifers fed 20% WSC diets had greater (P < 0.01) DMI, but ADG and G:F were not affected (P >= 0.11) by WSC concentration. The percentage of carcasses grading USDA Choice tended to be lower (P = 0.07) for cattle fed diets with 20 versus 0% WSC. Increasing dietary WDGS decreased G:F (P < 0.01) and tended to decrease ADG (P = 0.10), increased DMI (P = 0.08), and decreased hot carcass weight (P = 0.09). Dietary WSC affected ruminal pH (P < 0.01) and VFA molar concentrations (P = 0.05). Ruminal acetate: propionate decreased (quadratic, P < 0.03) with increasing WDGS. Bacterial diversity was not affected by WSC (P = 0.63) but increased with increasing WDGS (P = 0.01).Implications and Applications: Substituting SFC with 20% WSC in cattle finishing diets did not affect animal performance but decreased carcass quality. In contrast, increasing dietary WDGS decreased animal performance but did not affect carcass characteristics.