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

Authors: MCDANIEL, M - New Mexico State University; TRACEY, L - New Mexico State University; COLE, N - Retired ARS Employee; IVEY, S - New Mexico State University; LOEST, C - New Mexico State University

Submitted to: Applied Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/31/2021
Publication Date: 3/23/2021
Citation: McDaniel, M.R., Tracey, L.N., Cole, N.A., Ivey, S.L., Loest, C.A. 2021. Evaluation of whole corn substitution in diets based on steam-flaked corn containing different concentrations of wet distillers grains with solubles for beef cattle. Applied Animal Science. 37(2):140-154. https://doi.org/10.15232/aas.2020-02124.
DOI: https://doi.org/10.15232/aas.2020-02124

Interpretive Summary: Steam flaking corn (SFC) for feedlot finishing diets is a common grain processing method that increases corn’s energy value by 10 to 18 percent compared with dry-rolled corn-based diets (DRC). It is possible that grain processing costs associated with steam flaking can be partly decreased without compromising cattle performance by substituting a portion of the steam flaked corn with less processed grain in diets containing wet distillers grains with solubles (WDGS). Scientists from USDA-ARS (Bushland, Texas) and New Mexico State University studied the effects of substituting whole shelled corn (WSC) for steam flaked corn in beef cattle finishing diets containing different concentrations of WDGS. Substituting SFC with 20 percent WSC in finishing diets did not affect animal average daily gain or feed conversion, but decreased carcass quality. Dry matter intakes, and thus animal performance, were less than expected. The cause for this poor performance was not clear. Thus, it was not clear if replacing a portion of steam flaked corn with a less fermentable grain source, or possibly flaking corn to a greater flake density and lower starch availability, could reduce grain processing costs.

Technical Abstract: 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 ruminal 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 FSC-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 afffect animal performance but decreased carcass quality. In contrast, increasing dietary WDGS decreased animal performance but did not affect carcass characteristics.