Effects of reduced-fat modified wet distillers grains with solubles on beef steer performance and carcass composition

Two experiments were conducted to examine feedlot performance and carcass characteristics of beef steers fed reduced-fat, modified wet distillers grains with solubles (RMDGS). Angus cross steers were stratified by BW in each experiment and assigned to 20 pens containing either 6 or 7 steers per pen. In Exp. 1, pens were randomly assigned to 1 of 4 diets containing 15% corn silage and 1) 25.0% RMDGS and 57.04% whole shelled corn (25 RMDGS); 2) 40.0% RMDGS and 42.69% whole shelled corn (40 RMDGS); 3) 70.0% RMDGS and 12.49% whole shelled corn, fed 84 d, then switched to 40 RMDGS (70/40 RMDGS); 4) 70.0% RMDGS and 12.49% whole shelled corn (70 RMDGS). In Exp. 2, the same diets were fed except 70/40 RMDGS was replaced with a diet containing 73.16% whole shelled corn and 9.60% soybean meal (0 RMDGS). In Exp. 1, no significant differences in DMI, ADG, G:F, or carcass characteristics were found. In Exp. 2, DMI increased (P = 0.003) with increasing RMDGS. In Exp. 2, LM samples from 2 steers in each pen at each slaughter date were analyzed. There were no differences (P > 0.05) in percentage of moisture, fat, or cooking loss in shear force of rib steaks among treatments. Steers fed the 70 RMDGS diet produced rib steaks with lower a* (P < 0.05) following 7 d of chilled storage. Fatty acid analysis showed an increase (P < 0.05) in SFA at the expense of MUFA because of RMDGS supplementation. Increases were observed in PUFA, PUFA/SFA, conjugated linoleic acid, and omega-6 fats, with increasing RMDGS. Steers fed 70 RMDGS had inconsistent feedlot performance with a trend for lighter HCW, lower QG, and reduced meat quality.