Effects of concentration and source of wet distillers grains on digestibility of steam-flaked corn-based diets fed to finishing steers1

The source and dietary concentration of wet distillers grains may affect the digestibility of beef cattle finishing diets. The objectives of this experiment were to evaluate the effects of graded levels of sorghum+corn-based wet distillers grains plus solubles (NMDGS) and corn-based distillers grains plus solubles (CDGS) on digestibility of steam-flaked-corn-based diets fed to finishing beef steers and to determine potential effects on ammonia emission from feces and urine. Ten beef steers (average BW = 252 kg) were used in a replicated 5 × 5 Latin square design. Steers were fed diets containing increasing concentrations of NMDGS (0, 5, 10, or 15% of DM) or one concentration of CDGS (10% of DM), which replaced steam-flaked corn, cottonseed meal, and urea in a high-concentrate finishing diet. Apparent digestibilities of DM, OM, ash, N, P, ether extract, and NDF were quadratically affected by dietary NMDGS concentration, with lowest values for the 5 and 10% NMDGS diets and highest values for the 0 and 15% NMDGS diets. Digestibilities of DM, OM, ash, N, P, and NDF in the 10% NMDGS diet were not different (P > 0.10) from digestibility of the 10% CDGS diet. Digestibilities of CDGS and NMDGS, determined by difference, were not different (P > 0.10). In vitro ammonia losses tended (P < 0.09) to increase with increased NMDGS in the diet. Results of this study suggest that the digestibilities of NMDGS and CDGS are similar, and, at the concentrations used in this study, wet distillers grains plus solubles have only minor-effects on total-tract digestibility of diets based on steam-flaked corn.