The effects of zilpaterol hydrochloride on carcass cutability and tenderness of calf-fed Holstein steers

To evaluate the impact of zilpaterol hydrochloride (ZH) on carcass cutability and tenderness of calf-fed Holstein steers, calf-fed Holstein carcasses (n = 102) were selected from a pool of 2,300 steers that were fed 0 or 8.3 mg/kg (DM basis) of ZH. Zilpaterol hydrochloride was supplemented the last 20 d of the finishing period and withdrawn for 3 d before slaughter. Carcasses were selected based on carcass weight as well as predetermined USDA Yield grade categories. For tenderness evaluation, steaks from the strip loin, bottom round, and top round (n = 54 per subprimal) were aged for 14 or 21 d postmortem. Carcasses from ZH-fed steers had more (P < 0.01) saleable yield than carcasses from control-fed steers. Additionally, ZH-fed steers had greater (P <= 0.01) subprimal yield from the shoulder clod, strip loin, peeled tenderloin, top sirloin butt, bottom sirloin tri-tip, peeled knuckle, inside round, bottom round flat, eye of round, heel, and shank. Furthermore, ZH decreased (P < 0.01) the total amount and percentage of bone and fat trim from the carcass. Moisture loss was not affected by ZH in LM or inside round steaks (P > 0.05); however, ZH increased thawing loss (P = 0.05) but reduced cooking loss (P = 0.05) in bottom round steaks. Shear force values of LM and inside round steaks increased with ZH inclusion (P < 0.01), but there was no difference in bottom round steaks (P > 0.05). Steaks aged for 21 d had smaller (P < 0.01) Warner-Bratzler shear force (WBS) values than 14-d steaks from all 3 subprimals. Trained sensory panelists did not detect any differences (P > 0.05) in sensory juiciness, tenderness, or flavor variables of LM or inside round steaks, except ZH steaks from the LM received smaller scores for sustained juiciness (P = 0.01) and overall tenderness (P = 0.04) than control steaks. Although LM steaks from ZH cattle were tougher than control steaks, the ZH-treated steaks had an average WBS value of 4.10 kg, which would be classified as intermediate in tenderness, with trained panelists rating ZH steaks slightly to moderately tender. Feeding ZH improved carcass cutability of calf-fed Holstein steers; however, tenderness was reduced in LM and inside round steaks. The interaction of postmortem tenderization techniques should be investigated to evaluate their impact on palatability in cattle supplemented with beta-agonists to allow the beef industry to take full advantage of the enhancement in performance and carcass yield.