Evaluation of whole corn substitution in diets based on steam-flaked corn containing different concentrations of wet distillers grains with solubles for beef cattle

Abstract

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. The study used 642 Angus-cross heifers (411.7 ± 18.0 kg of initial BW) assigned to 36 pens. Treatments (2 × 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. 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). 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.