Effects of steam-flaked corn and wet distillers grains with solubles on energy metabolism of finishing beef steers

Objective: Wet distillers grains with solubles (WDGS) are a common feed ingredient used in cattle finishing diets. However, the NE values of WDGS have not been clearly delineated, and there may be an interaction between grain processing method and the feeding value of WDGS. This study was conducted to evaluate the relative NE values of WDGS and to evaluate possible associative effects between WDGS and steam -flaked corn (SFC) on energy and nitrogen utilization by finishing beef steers. Materials and Methods: Four British crossbred steers were used in a 4 x 4 Latin square design in which steers were fed 1 of 4 diets: (1) a basal 86% concentrate diet fed a 1x maintenance (B), (2) the basal diet + SFC fed at 1.5x maintenance (B+SFC), (3) the basal diet + WDGS fed at 1.5x maintenance (B+WDGS), and (4) the basal diet + a 50:50 blend of WDGS and SFC fed at 1.5x maintenance (BLEND). Each period of the Latin square was 28 d in length with steers confined to indirect opencircuit respiration chambers the last 5 d of each period. Nutrient digestibility, urinary nutrient excretion, methane and carbon dioxide production, and heat production were determined during the last 5 d of each period. Dietary and ingredient (SFC or WDGS) TDN, DE, ME, and NE values were calculated. Results and Discussion: The digestibility of DM and OM of B+SFC was greater than that of B+WDGS, with the BLEND diet being intermediate. Nitrogen balance was numerically greater for B+WDGS than for B+SFC, with BLEND being intermediate. Digestible energy, ME, and energy retention were greater for B+SFC than for B+WDGS, with BLEND being intermediate. The experimental method used affected the TDN, DE, ME, and NE values of diets, SFC, and WDGS. There were negative associative effects (-1% to -8.0%) between SFC and WDGS for energy values. Actual DE: TDN averaged 4.11 Mcal of DE/kg of TDN, which is less than the 4.4 value used by NASEM (2016). The DE: digestible OM ratio averaged 4.54 Mcal/kg, and the digestible OM: TDN ratio averaged 90.2. Implications and Applications: Our results suggest that within the range of rations fed in this study, the NE values for WDGS by NASEM (2016) may overestimate their relative NE (15%) when fed in diets based on SFC.