Effects of corn grain processing method and dietary inclusion of wet distillers grains with solubles on energy, carbon, nitrogen, and nutrient balance of steers fed at maintenance

Because of the establishment of the ethanol industry in the Southern Great Plains, wet distillers grains with solubles (WDGS) have become a common ingredient in beef cattle finishing diets (Samuelson et al., 2016). The objectives of this study were to determine the effects of corn processing methods and WDGS concentration on energy, carbon (C) nitrogen (N), and nutrient balance using 4 Jersey steers in respiration calorimetry chambers. A 2 × 2 factorial arrangement of treatments was used in a Latin square design. The 4 treatment combinations were: 1) SFC diet with 0% WDGS (SFC-0); 2) SFC diet with 30% WDGS (SFC-30); 3) DRC diet with 0% WDGS (DRC-0); and 4) DRC diet with 30% WDGS (DRC-30). Diets were balanced for ruminally degradable protein (RDP) and ether extract (EE) by the addition of cottonseed meal and yellow grease. No interactions between grain processing method and WDGS inclusion were detected for energy, N, and C balance, or nutrient digestibility (P ≥ 0.12). As a proportion of gross energy intake (GEI), retained energy was greater in steers fed SFC than DRC, with the greatest values observed for SFC-30 and the least for DRC-0 (P =0.03). Digestible energy as a proportion of GEI did not differ among treatments (P = 0.21). Metabolizable energy as a proportion of GEI was not affected by treatment (P = 0.19). Steers fed SFC-30 and DRC-30 had greater N intake (P ≤ 0.05) than steers fed the corresponding 0% WDGS diets. Apparent EE digestion was also greater for the SFC-30 and DRC-30 than for the SFC-0 and DRC-0 (P = 0.02), although apparent EE digestibility as a percentage of intake was not affected by diet (P = 0.15). Overall, these results indicate that corn processing method had a larger influence on energy use, whereas WDGS inclusion primarily changed nutrient intake and digestibility in steers fed at maintenance.