Effects of Feeding Isolated Nutritional Components in Distillers Grains on Growing Cattle Performance

Abstract Text: The nutrient composition of distillers grains plus solubles (DGS) continues to change as ethanol producers may remove oil and fiber from DGS. Removal of these components may alter the energy content of DGS and, therefore, its value as a feedstuff. An experiment was conducted to evaluate the effects of fat, fiber, and protein found in distillers grains on performance of growing crossbred steers (n=450; initial BW= 297, SD= 24 kg). All growing diets contained 50% grass hay, 5% Soypass® to meet protein requirements, and 5% supplement (DM basis). Treatments included a 40% corn control diet, a diet containing 40% modified distillers grains plus solubles (MDGS) replacing dry-rolled corn, or one of four diets designed to isolate the contribution of fiber, protein, or solubles to compare to the feeding value of MDGS. The four diets consisted of: 1) corn gluten meal replacing 20% corn to mimic the protein content of MDGS (PROT); 2) a combination of 16.4% corn bran and 3.6% germ meal to represent fiber in MDGS (FIB); 3) condensed distillers solubles included at 15% (SOL); and 4) a combination of FIB and SOL together (COMBO). Cattle were fed 81 d and performance data were analyzed by pen using the MIXED procedure of SAS. Ending BW, ADG, and G:F were influenced by treatment (P < 0.02). Treatment tended (P = 0.06) to impact DMI, which was greater for MDGS, SOL, and COMBO compared to FIB (P < 0.04). Steers fed MDGS had the greatest ADG while FIB had the least (P < 0.01). Feed efficiency was improved for steers fed MDGS and PROT, intermediate for FIB, and poorest for CON, SOL, and COMBO diets (P < 0.02). Ending BW was heaviest for MDGS and lightest for CON and FIB (P < 0.01). All remaining treatments had intermediate ending BW with PROT being greater compared to SOL or COMBO (P< 0.01). Cattle fed 40% MDGS performed better than those fed CON. Though all diets met the metabolizable protein requirements of the steers, PROT resulted in feed conversions similar to MDGS.  This suggests that protein in MDGS, when overfed to provide energy, explains improved performance of cattle fed MDGS in high forage diets. No other component appeared to contribute toward the greater energy value of MDGS relative to corn. Data from this study suggest that excess metabolizable protein as RUP contributes significantly to the feeding value of MDGS in growing diets.

Keywords: Distillers Grains, Energy, Protein