Evaluation of the relative contribution of protein in distillers grains in finishing diets on performance and carcass characteristics

Abstract Text: Crossbred calf-fed steers (n = 324; initial BW = 291 kg; SD = 24 kg) were utilized in a randomized block design to evaluate the energetic contributions of protein from wet distillers grains plus solubles (WDGS) on feedlot performance and carcass characteristics. Pen was the experimental unit and initial BW block (n = 2) was treated as a fixed effect. Pens within block were assigned randomly to one of six treatments (6 replications) for a total of 36 pens (9 steers/pen). The protein portion of WDGS was simulated using corn gluten meal (CGM; 8.75 and 17.5% inclusion; DM basis) to provide similar dietary protein concentration as 20 and 40% WDGS inclusion (DM basis). Linear and quadratic effects of WDGS inclusion and protein (CGM) concentration were evaluated. Pre-planned pairwise comparisons were used to determine effects of solubles inclusion to 17.5% CGM diet and feeding value of protein from WDGS. A linear decrease (P < 0.01) in DMI was observed as WDGS inclusion increased from 0% in the control (10.3 kg) to 40% (9.7 kg); G:F increased linearly (P < 0.01) as WDGS increased from 0% (0.161) to 40% (0.176). A quadratic increase (P = 0.04) in ADG was observed as CGM increased from 0% (1.65 kg) to 17.5% (1.73 kg). A linear increase (P < 0.01) in G:F was observed as CGM (protein) increased from 0% (0.161) to 17.5% (0.169). Addition of 10% solubles (DM basis) to the 17.5% CGM diet decreased (P = 0.04) ADG. Isolating the protein portion of 20% WDGS by feeding 8.75% CGM decreased (P < 0.01) G:F compared to 20% WDGS. Similarly, protein from 40% WDGS replaced by 17.5% CGM increased (P < 0.01) DMI and decreased (P < 0.01) G:F compared to 40% WDGS. A quadratic response (P = 0.04) in HCW was observed as CGM increased from 0% (378 kg) to 17.5% (388 kg). The inclusion of solubles decreased (P = 0.04) HCW when added to 17.5% CGM. Using the calculated G:F of 0.161 for the control, 20% WDGS has 134% the feeding value of corn. Similarly the calculated feeding values relative to corn were: 125%, 110%, 129%, and 121% for, 40% WDGS, 8.75% CGM, 17.5% CGM, and 17.5% CGM with 10% solubles, respectively. Excess protein used as an energy source from distillers grains accounts for the majority of the feeding value response observed when feeding WDGS.

Keywords: distillers grains plus solubles, energy, protein