Comparative effects of supplementing beef steers with zilpaterol hydrochloride, ractopamine hydrochloride, or no beta agonist on strip loin composition, raw and cooked color properties, shear force, and consumer assessment of steaks aged for fourteen or twenty-one days postmortem

: Beef steers (n = 1,914) were assigned to 1 of 3 β-adrenergic agonist (βAA) supplementation treatments-zilpaterol hydrochloride (ZH; 8.3 mg/kg of DM for 20 d with 3-d withdrawal), ractopamine hydrochloride (RH; 308 mg·head(-1)·d(-1) for 28 d), or no βAA (CON)-to determine the effects on consumer eating quality. Strip loins (n = 1,101; CON = 400, RH = 355, and ZH = 346) were obtained and fabricated into 2.5-cm-thick steaks for proximate, Warner-Bratzler shear force (WBSF), slice shear force (SSF), and consumer analyses; steaks were aged until 14 or 21 d postmortem. Fat and moisture contents were not affected by βAA supplementation (P > 0.05), but strip steaks from steers fed ZH had more protein (P 0.05). In steaks aged 21 d, feeding βAA influenced (P 0.05) acceptability. Quality grade impacted (P < 0.01) all traits and acceptability in steaks aged 14 and 21 d. In 14-d steaks, Premium Choice typically was scored higher than Low Choice or Select; however, consumers rated 21-d Low Choice and Premium Choice similarly-both receiving greater scores than Select. Consumers detected several differences in eating quality at 14 d because of βAA supplementation. Increasing aging from 14 to 21 d mitigated differences in shear force and tenderness scores because of feeding ZH, so that tenderness and overall acceptability were similar between ZH, RH, and CON.