Increasing dietary roughage equivalent from 7 to 12% during the final 28 days on feed does not impact growth performance but may improve ruminal health in feedlot steers

Abstract The objective was to determine if increasing roughage equivalent (RE) from 7% to 12% (17.5 to 20.5% dietary neutral detergent fiber on a DM basis) in the last 28 days of fattening could improve rumen health parameters and decrease the frequency of liver abscesses without compromising productive efficiency or carcass characteristics. Charolais × Angus crossbred steers [n = 64; n = 8 pens; initial shrunk body weight (SBW) = 633 kg ± 35.1 kg] were allocated to dietary treatment in a completely randomized design. All steers were fed a common 7% [dry matter (DM) basis] roughage equivalent diet (17.5% neutral detergent fiber [NDF] DM basis) where the roughage sources were based upon corn silage and hay for the 58 d prior to study initiation. The treatments involved increasing the dietary forage concentration from 7% to 12% for the final 28 days on feed, as follows: 1) No diet change (7R) and 2) 5% (DM basis) roughage equivalent addition to 7R via grass hay during the final 28 DOF to increase the dietary NDF to 20.5% DM basis (12R). Steers were finished on treatment diets for 28 d prior to harvest. No differences (P ≥ 0.19) were observed for any growth performance, efficiency, or carcass trait measures except for marbling scores. Marbling score differed (P = 0.04) between treatments with 12R steers exhibiting 5% greater marbling than 7R steers. A treatment × DOF interaction (P < 0.01) was observed for minutes ruminating per day. Daily minutes ruminating was increased (P ≤ 0.05) for 12R on d 1, 2, and 20 and tended to be increased (P ≤ 0.10) for 12R on d 10, 13, 24, and 25. Rumenitis score nor liver abscess prevalence was influenced by dietary treatment. Inclusion of an additional 5% RE to cattle diets during the final 28 DOF can be a management strategy to maintain ruminal health without sacrificing growth performance or carcass quality, but does not appear to reduce incidence of liver abscessation.