| In the first study, hot carcass weight (HCW), dressing percentage, 12th rib backfat, longissimus muscle (LM) area, marbling score, semitendinosus (ST), and Warner-Bratzler Shear Force (WBSF) values were investigated in finishing steers classified as high or low efficiency using residual feed intake (RFI). Individual intake for steers was recorded. The 20% most efficient and least efficient were selected for slaughter. Dressing percentage tended to be greater in high efficiency steers than low efficiency steers. LM area and LM area relative to BW (cm2/kg) was affected by year (P ≤ 0.02). There were no differences in HCW, 12th rib fat, WBSF, or ST weight relative to BW. Data from this study suggests that producers could select for high efficiency cattle without compromising carcass quality.;In addition to genetically selecting cattle for improved efficiency, producers also utilize many technologies. The use of beta-agonists at the end of the feeding period has been common in the beef industry. The second study was a 2 x 2 factorial in which cattle were housed in two pen types (open or shaded). Half the cattle across pens received Zilpaterol hydrochloride (ZH) in the last 21 d of the feeding period. Slice shear force (SSF) was determined on steaks from strip loins at 14 d and 35 d postmortem. In-home consumer evaluations were completed at the same postmortem aging periods. Cattle fed ZH had increased SSF and lower consumer ratings. Steaks aged longer had lower SSF and higher consumer ratings. These data show that inclusion of ZH can negatively impact beef tenderness and consumer acceptance.;The third study investigated the relationship between beef quality grade programs, SSF, and postmortem proteolysis. Steaks originated from 2 plants and represented 7 quality grades. At 21 d postmortem, SSF was determined. Postmortem proteolysis was analyzed by determining the percentage of desmin degradation. The plant affected LM SSF, sarcomere length, and the percentage of desmin degraded. Quality grade program did affect SSF and sarcomere length, but not the percentage of desmin degradation. This research shows that quality grade program can be effective in grouping carcasses with similar LM SSF. |
