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An experiment was conducted to determine the effects of zilpaterol hydrochloride mM supplementation (ZH; 8.3 mg/kg on a DM basis for 20 d) and calcium chloride injection [CaCl(2), 200 at 5% (wt/wt) at 72 h postmortem] on palatability traits of beef (Bos taurus) strip loin steaks. Select (USDA) strip loins were obtained from control (no ZH = 19) and ZH-supplemented carcasses (n = 20). Right and left sides were selected alternatively to serve as a control (no INJ) or CaCl(2)-injected (INJ) and stored at 4°C. Before injecting the subprimals (72 h postmortem), 2 steaks were cut for proximate, sarcomere length, and myofibrillar fragmentation index (MFI) analyses. At 7 d postmortem each strip loin was portioned into steaks, vacuum packaged, and aged for the appropriate period for Warner-Bratzler shear force (WBSF; 7, 14, 21, and 28 d postmortem), trained sensory analysis (14 and 21 d postmortem), purge loss (7 d), and MFI (3, 7, 14, 21, and 28 d postmortem). Results indicated steaks from both ZH supplementation and INJ had reduced WBSF values as days of postmortem aging increased. The WBSF values of ZH steaks were greater (P < 0.05) than no ZH steaks at each postmortem aging period. The INJ steaks had lower WBSF values (P < 0.05) than non-injected steaks. A greater percentage (91 vs. 71%) of steaks had WBSF values < 4.6 kg from steers with no ZH supplementation at 7 d postmortem, but the percentage did not differ (P > 0.05) due to ZH at 14, 21, or 28 d or due to INJ at any aging period. Trained panelists rated tenderness less in ZH steaks than steaks with no ZH at 14 d and 21 d. However, INJ improved (P < 0.05) the tenderness ratings and flavor intensity of the trained panelists, compared with their non-injected cohorts at 21 d. Zilpaterol hydrochloride supplementation reduced (P < 0.05) MFI values, but INJ resulted in greater (P < 0.05) MFI values compared with no INJ. Subprimals from ZH and INJ showed greater purge loss (P < 0.05). Although no interactions were found with ZH and CaCl(2), injecting USDA Select strip loins from ZH-fed cattle can help reduce the normal WBSF variation as it does in steaks from non-ZH-fed cattle.

British × Continental heifers (n = 3,382; initial BW = 307 kg) were serially slaughtered to determine if increasing days on the finishing diet (DOF) mitigates negative consequences of zilpaterol HCl (ZH) on quality grade and tenderness of beef. A 2 × 3 factorial arrangement of treatments in a completely randomized block design (36 pens; 6 pens/treatment) was used. Zilpaterol HCl (8.33 mg/kg DM) was fed 0 and 20 to 22 d before slaughter plus a 3 to 5 d withdrawal to heifers spending 127, 148, and 167 DOF. Feedlot and carcass performance data were analyzed with pen as the experimental unit. Three hundred sixty carcasses (60 carcasses/treatment) were randomly subsampled, and strip loin steaks were aged for 7, 14, and 21 d for assessment of Warner-Bratzler shear force (WBSF) and slice shear force (SSF) with carcass serving as the experimental unit for analysis. No relevant ZH × DOF interactions were detected (P > 0.05). Feeding ZH during the treatment period increased ADG by 9.5%, G:F by 12.5%, carcass ADG by 33.6%, carcass G:F by 35.9%, carcass ADG:live ADG by 15.6%, HCW by 3.2% (345 vs. 356 kg), dressing percent by 1.5%, and LM area by 6.5% and decreased 12th-rib fat by 5.2% and yield grade (YG) by 0.27 units (P < 0.01). Feeding ZH tended to decrease marbling score (437 vs. 442 units; P = 0.10) and increased WBSF at 7 (4.25 vs. 3.47 kg; P < 0.01), 14 (3.57 vs. 3.05 kg; P < 0.01), and 21 d (3.50 vs. 3.03 kg; P < 0.01). Feeding ZH decreased empty body fat percentage (EBF; 29.7% vs. 30.3%; P < 0.01) and increased 28% EBF adjusted final BW (473.4 vs. 449.8 kg; P < 0.01). Analysis of interactive means indicated that the ZH × 148 DOF group had a similar percentage of USDA Prime, Premium Choice, Low Choice, and YG 1, 2, 3, 4, and 5 carcasses (P > 0.10) and decreased percentage of Select (30.4 vs. 36.6%; P = 0.03) and Standard (0.2 vs. 0.9%; P = 0.05) carcasses compared with the control × 127 DOF group. As a result of ZH shifting body composition, extending the DOF of beef heifers is an effective feeding strategy to equalize carcass grade distributions. This can be accomplished along with sustaining the ZH mediated advantages in feedlot and carcass weight gain.

The objective of this research was to evaluate changes in the muscle conformation of subprimal top-loins (M. longissimus lumborum) from calf-fed Holstein steers fed zilpaterol hydrochloride (ZH). Top-loins (n = 100) were transversely cut into 2.54 cm-thick steaks, weighed, and objectively evaluated via image analysis software for muscle area, width, and length traits. Top-loin steaks from steers fed ZH were heavier (P< 0.01; 367 vs. 337 g) and average muscle area per steak was greater (P < 0.05; 80.9 vs. 77.2 cm(2)) as compared to steaks from control steers. Muscle width (medial-lateral) was not different (P = 0.23) between control steers and those fed ZH. However, steaks from steers fed ZH had greater (P < 0.05) depth (dorsal-ventral) than steaks from control steers throughout the top-loin. The increased muscle depth of top-loins from calf-fed Holstein steers fed ZH may improve the center-of-the-plate salability of a cut that has traditionally suffered from poor muscling., (Copyright © 2010 The American Meat Science Association. Published by Elsevier Ltd. All rights reserved.)

The objective of this study was to determine the effect of feeding zilpaterol hydrochloride (ZH) on the shelf life and stability of ground beef. Beef knuckles and plates were obtained from USDA Select beef heifer carcasses from control (CON) animals or those supplemented with ZH (8.33 mg/kg of dietary DM basis) for the last 20 d of the finishing period. Subprimals were coarsely ground and blended to produce an 80% lean product. The mixture was vacuum-stuffed into chubs and placed in dark storage at 2 to 4°C for 7, 14, or 21 d before fine grinding. Each week, the finely ground samples were packaged on expanded polystyrene trays overwrapped with polyvinyl chloride film and placed in refrigerated retail cases (0 to 2°C) under continuous fluorescent lighting to simulate retail display. Samples were subjected to a variety of analyses at different time intervals (h) during simulated display, including composition analysis, thiobarbituric acid-reacting substance analysis (TBA), sensory color, instrumental color, and aerobic plate count. Data analysis revealed trained sensory color and discoloration scores were similar between CON and ZH-treated samples. Instrumental L* and b* values for CON and ZH-treated samples did not differ (P = 0.13 and 0.19, respectively). Instrumental a* values declined (P < 0.05) over the display period for CON and ZH ground beef. However, a* values for ZH ground beef stored for 7 d were greater (P < 0.05) than CON values at 18 through 72 h of display. There was a treatment × storage day interaction (P < 0.001) for TBA values with ZH having smaller TBA values than CON after 7 d of dark storage. There was no difference (P = 0.21) in aerobic plate count between ZH and CON ground beef samples. Overall, ground beef from cattle supplemented with ZH was equal to or better than CON for sensory color and discoloration, instrumental color, and stability variables, including TBA reactive substances and aerobic plate counts.

Longissimus lumborum (LL) muscles from 117 steers plus LL, gluteus medius (GM), and triceps brachii (TB) muscles from 132 heifers were evaluated for effects of feeding duration of zilpaterol hydrochloride (Zilmax(R); ZH; 7.56g/907kg on a dry matter basis) and aging time on tenderness. Both genders were blocked by initial weight into six blocks of four pens. Pens were assigned to treatments of control (C), or 20, 30 or 40days on ZH, with a 3day withdrawal. Steaks from each subprimal were vacuum aged individually for 7, 14 or 21days, frozen, thawed, and cooked to 71 degrees C for Warner-Bratzler shear force (WBSF). All muscles from steers and heifers from ZH30 and ZH40 treatments had higher (P<0.05) WBSF than those of C. The WBSF of steer LL and heifer TB from the ZH20 treatment was higher (P<0.05) than C. There was a treatment by aging interaction (P>0.05) for WBSF of GM steaks from heifers. Percentage of intramuscular fat had little effect on tenderness. Percentages of steer LL and heifer TB steaks with WBSF values below thresholds of either 5.0 or 4.6kg from the ZH20 treatment were quite high, whereas percentages of heifer LL and GM muscles below 5.0kg (67%) and 4.6kg (57%) were low. Feeding ZH20days generally increased WBSF values, but mean WBSF values for steer LL and heifer TB were below 4.6kg. Feeding ZH 20days resulted in>40% of GM steaks with WBSF values above 4.6kg., (Published by Elsevier Ltd.)

Analyses were conducted to evaluate the ability of the USDA yield grade equation to detect differences in subprimal yield of beef-type steers and calf-fed Holstein steers that had been fed zilpaterol hydrochloride (ZH; Intervet Inc., Millsboro, DE) as well as those that had not been fed ZH. Beef-type steer (n = 801) and calf-fed Holstein steer (n = 235) carcasses were fabricated into subprimal cuts and trim. Simple correlations between calculated yield grades and total red meat yields ranged from -0.56 to -0.62 for beef-type steers. Reliable correlations from calf-fed Holstein steers were unobtainable; the probability of a type I error met or exceeded 0.39. Linear models were developed for the beef-type steers to predict total red meat yield based on calculated USDA yield grade within each ZH duration. At an average calculated USDA yield grade of 2.9, beef-type steer carcasses that had not been fed ZH had an estimated 69.4% red meat yield, whereas those fed ZH had an estimated 70.7% red meat yield. These results indicate that feeding ZH increased red meat yield by 1.3% at a constant calculated yield grade. However, these data also suggest that the calculated USDA yield grade score is a poor and variable estimator (adjusted R(2) of 0.31 to 0.38) of total red meat yield of beef-type steer carcasses, regardless of ZH feeding. Moreover, no relationship existed (adjusted R(2) of 0.00 to 0.01) for calf-fed Holstein steer carcasses, suggesting the USDA yield grade is not a valid estimate of calf-fed Holstein red meat yield.

Beef steers (n = 11,877) from 7 studies were fed zilpaterol hydrochloride (ZH) for 0 or 20 to 40 d before slaughter to determine the effects of ZH on subprimal weight and yield. Carcasses were selected based on mean HCW of treatment groups for fabrication into boneless, closely trimmed, or denuded subprimals, lean, fat, and bone. Data from the 7 trials were pooled for statistical analysis. Feeding ZH increased (P < 0.05) weights of all major subprimals compared with steers not supplemented with ZH. Also, subprimals from the hindquarter, including valuable cuts like the tenderloin, strip loin, and top sirloin butt, increased (P < 0.05) as a percentage of cold carcass weight from steers fed ZH. The tenderloin was 0.06 percentage units greater (P < 0.05), the strip loin was 0.08 percentage units greater (P < 0.05), and the top sirloin butt was 0.11 percentage units greater (P < 0.05) in ZH-fed steers when compared with steers not fed ZH. Supplementation of ZH greatly increased (P < 0.05) total saleable carcass yield by 1.76 percentage units, whereas ZH inclusion decreased (P < 0.05) the percentage of fat trim and bone by 0.58 and 1.10 percentage units, respectively. Therefore, ZH can be utilized by the beef industry to improve red meat yield efficiency throughout the beef production chain.

Two trials investigated zilpaterol hydrochloride (ZH) feeding duration, enhancement, blade tenderization, and postmortem aging effect on Warner-Bratzler shear force (WBSF; trial 1) and consumer sensory ratings (trial 2). For trial 1, USDA Select beef strip loins were obtained from carcasses of beef steers fed ZH (6.8 g/t on 90% DM) the last 0, 20, 30, or 40 d of the feeding period. One-half of each strip loin was enhanced (110%) with a brine solution, whereas the remaining portion was not enhanced. Both pieces were portioned into steaks, which were aged 7, 14, or 21 d for WBSF analysis. For trial 2, paired USDA Select beef strip loins were obtained from carcasses of beef steers fed ZH the last 0 or 20 d of feeding. Paired strip loins were fabricated into 4 pieces and assigned to control, moisture enhanced, blade tenderized, and blade tenderized + moisture enhanced treatments. Strip loin pieces were then portioned into steaks that were aged 14 or 21 d postmortem. Consumers panelists (n = 458) indicated their like or dislike of tenderness, juiciness, flavor, and overall like of each sample using 8-point, verbally anchored scales, as well as tenderness and overall acceptability. With exception of 20 d ZH-treated steaks, results from trial 1 indicate WBSF values decreased (P < 0.05) with enhancement. Among enhanced steaks, steaks from cattle fed ZH for 20, 30, and 40 d had greater (P < 0.05) WBSF values than controls. Among nonenhanced steaks, 20 d ZH-treated steaks had WBSF values similar to 0, 30, and 40 d ZH-treated steaks, whereas 30 and 40 d ZH-treated steaks had greater (P < 0.05) WBSF values than controls. Postmortem aging for 21 d improved (P < 0.05) WBSF values for all ZH durations when compared with 7-d aging treatments. Results from trial 2 indicate ZH feeding for 20 d had no effect on flavor scores, decreased tenderness scores (P < 0.05), and tended (P < 0.10) to decrease juiciness and overall like scores when compared with controls for steaks aged 14 d. After 21 d aging, steaks from 20 d ZH-fed cattle had reduced (P < 0.05) tenderness, juiciness, and overall like scores and tended (P < 0.10) to have decreased flavor scores when compared with controls. These results indicate enhancement improved WBSF, but was not sufficient to overcome the detrimental effect of ZH feeding duration on WBSF until steaks were aged for 21 d postmortem. Consumer scores indicate 20 d ZH feeding had no effect on overall acceptability, but decreased tenderness and tenderness acceptability scores when compared with controls.

Two studies using beef and calf-fed Holstein cattle were conducted to determine the effect of zilpaterol hydrochloride (ZH) supplementation on the color of strip loin steaks packaged in traditional and modified-atmosphere packaging. Select (USDA) strip loins were obtained from the carcasses of beef (n = 118) or calf-fed Holstein (n = 132) cattle fed ZH (6.8 g/ton on a 90% DM basis) for the last 0, 20, 30, or 40 d of feeding. One portion of the strip loin was moisture enhanced, cut into steaks, and packaged in an atmosphere containing 80% oxygen and 20% carbon dioxide. The remaining portion of the strip loin was vacuum-packaged until further processing. At 14 d postmortem, the vacuum-packaged loins were portioned and packaged in traditional retail packaging. Traditionally packaged and modified-atmosphere-packaged steaks were then placed in retail cases at -1 to 3 degrees C for 5 d and evaluated by both trained and consumer panelists. Instrumental color values and purge loss were also recorded. Zilpaterol hydrochloride duration had no effect on the color and purchase intention scores of consumer panelists for beef and calf-fed Holstein strip loin steaks. Zilpaterol hydrochloride feeding duration had no effect on the color or discoloration scores of trained panelists for enhanced, modified-atmosphere-packaged beef strip steaks. Traditionally packaged beef steaks from cattle treated with ZH for 20 d had more desirable (P < 0.05) lean color scores than steaks from cattle not treated with ZH on d 2, 3, and 4 of display and had similar discoloration scores on d 1, 2, and 3 of display. The color scores of trained panelists for enhanced calf-fed Holstein steaks were more desirable (P < 0.05) for steaks from cattle not treated with ZH than for steaks from cattle treated with ZH for 20 d on d 1, 2, 3, and 4 of display. However, the discoloration scores of trained panelists for enhanced and modified-atmosphere-packaged calf-fed Holstein steaks were similar for steaks from cattle treated with ZH for 0 and 20 d on d 1, 2, and 3 of display. The scores of trained panelists indicated that traditionally packaged steaks from calf-fed Holsteins treated with ZH for 0 d had a darker lean color (P < 0.05) than steaks from ZH-treated cattle on d 1 of display, whereas the lean color scores for ZH treatments of all durations were similar on d 4 of display. The scores of trained panelists indicated that ZH treatment had no effect on the discoloration of traditionally packaged, nonenhanced strip steaks from calf-fed Holsteins. Therefore, feeding ZH to beef or calf-fed Holstein steers had no detrimental effect on the lean color or color stability of strip loin steaks subjected to enhancement, packaged in modified-atmosphere or traditional packaging, and displayed under simulated retail conditions.

To determine the effects of zilpaterol hydrochloride (ZH; 6.8 g/t on 90% DM basis) feeding duration (0, 20, 30, and 40 d) on Warner-Bratzler shear force (WBSF) of longissimus lumborum (LL), triceps brachii (TB), and gluteus medius (GM) muscles, beef from feeding trials was collected and shipped to participating universities. Animals were slaughtered at commercial processing facilities across the United States. Strip loin, shoulder clod, and top sirloin butt subprimals (IMPS 180, 114, and 184, respectively) were obtained from a portion of USDA Choice and Select grade carcasses for WBSF using standardized procedures and equipment. Feeding ZH increased (P < 0.001) LL WBSF values of USDA Choice and Select steaks. A significant linear contrast existed for both quality grades, indicating increased WBSF values were associated with longer feeding durations. Increased postmortem aging decreased LL WBSF of control and treated steaks. Postmortem aging from 7 to 21 d decreased LL WBSF values by 17.6 and 16.4% for USDA Choice and Select steaks, respectively. The percentage of LL steaks from ZH-supplemented cattle with a WBSF value <4.5 kg was significantly less than control steaks for both quality grades. Postmortem aging from 7 to 21 d postmortem increased (P < 0.001) the percentage of LL Choice and Select steaks with WBSF <4.5 kg for all ZH feeding durations. Feeding ZH for 20, 30, or 40 d increased (P < 0.01) WBSF of USDA Choice TB and GM steaks compared with 0-d controls. Feeding ZH for 0, 20, and 40 d had a similar effect on WBSF of USDA Select GM steaks, and produced lesser values than steaks from cattle fed ZH for 30 d. Feeding ZH for 20, 30, and 40 d had no effect on WBSF values of USDA Select TB steaks. However, the 20-, 30-, and 40-d duration produced WBSF values greater (P < 0.05) than control (0 d) TB steaks. Postmortem aging decreased (P < 0.05) WBSF of USDA Choice and Select TB and GM steaks, but the percentage improvement in WBSF attributed to aging was less than observed for LL steaks. The results of this study indicate feeding ZH increased (P < 0.001) WBSF of LL, TB, and GM. The ZH feeding also decreased (P < 0.01) the percentage of steaks with WBSF <4.5 kg regardless of US quality grade, whereas postmortem aging increased (P < 0.01) the percentage of US Choice and Select steaks with WBSF <4.5 kg. Finally, postmortem aging reduced (P < 0.05) WBSF of steaks from ZH-supplemented beef cattle.

Zilpaterol hydrochloride (ZH) is designed to increase carcass leanness, chilled side weight (CSW), and percent saleable yield. The objective of this study was to evaluate the effect of a single dose of ZH on cutability and subprimal yield of calf-fed Holstein steers when fed for increasing durations. Two hundred forty steers were fed 8.3 mg/kg of ZH on a DM basis for 0, 20, 30, or 40 d, with a 3-d withdrawal before slaughter. After slaughter, steers were fabricated into 4 pieces (round, loin/flank, rib/plate, and chuck), packaged in combos, shipped to 2 locations, and further fabricated into subprimal pieces and trim. Trim was collected from each primal and separated into groups based on composition of 90, 80, and 50% lean. Zilpaterol hydrochloride increased (P = 0.01) CSW by 6.22 kg and saleable yield by 6.4 kg when included in the diet for 20 d. Furthermore, saleable yield as a percentage of CSW was increased (P = 0.03) 1.18 percentage units when included in the diet for 20 d. Steers fed ZH for 20 d had heavier strip loins (4.47 vs. 4.12 kg, P = 0.02), tenderloins (2.75 vs. 2.49 kg, P = 0.02), and ribeye rolls (5.74 vs. 5.30 kg, P = 0.01) than steers not fed ZH. These advantages are further demonstrated as a percentage of CSW. Strip loins (P = 0.06), tenderloins (P = 0.04), and ribeye rolls (P = 0.04) of ZH-fed steers had a greater percentage of CSW than controls. Zilpaterol hydrochloride also increased the percentage of CSW of the 3 primary components of the round when fed for 20 d. The knuckle was 0.10 percentage units heavier (P = 0.11), the top round was 0.24 percentage units heavier (P = 0.04), and the bottom round was 0.22 percentage units heavier (P = 0.03) in ZH-fed steers when compared with steers not fed ZH. Based on these data, it can be concluded that ZH significantly increased subprimal cutting weights, yields, and percentage saleable yield of calf-fed Holstein steers when fed for at least 20 d before slaughter. Zilpaterol hydrochloride increased percentage of CSW of subprimal cuts from Holstein steers in the round and to a lesser degree in the loin.

The impact of zilpaterol hydrochloride (ZH) on carcass yield, composition, and tenderness was evaluated using 384 beef steers in a randomized complete block design. Main effects were the addition of 0 or 8.3 mg/kg of ZH for the final 20 d of feeding and each inclusion level was paired with withdrawal periods of 3, 10, 17, or 24 d. The 2 animals with BW closest to the pen average were selected for carcass fabrication to determine carcass yield, composition, and tenderness. The carcasses from animals fed ZH had greater (P = 0.008) individual side weights. Carcass fat determinations were unchanged (P = 0.70) by ZH. Weights of the strip loin (P = 0.01), peeled tenderloin (P = 0.02), and top sirloin butt (P < 0.001) were all improved with ZH. When expressed as a proportion of carcass weight, ZH increased percentage of carcass in the top sirloin butt (P = 0.006), bottom sirloin tri-tip (P = 0.02), top inside round (P = 0.002), bottom round flat (P = 0.001), and flank steak (P = 0.02). A longer withdrawal time (WT) increased (P < 0.001) carcass weights. Shoulder clod weights were greatest (P < 0.001) with 17-d WT from ZH, whereas chuck roll weights were greatest (P = 0.02) at 17 and 24 d of WT. Peeled tenderloins, top sirloin butts, and eye of rounds responded to WT, with increased (P < 0.001) weights seen at 10 d of WT as compared with all other WT. Shear force values were greater at each of the 3 aging times, 7 d (P < 0.001), 14 d (P < 0.001), and 21 d (P = 0.003), in steaks from ZH-fed steers compared with control steers. Protein percentages were greater in ZH steaks (P = 0.03) and ZH ground beef trim (P < 0.001). Percent moisture was increased (P < 0.001) in strip loin steaks at 3 and 10 d WT. Ground beef trim had an increase (P = 0.04) in percent moisture and a decrease (P = 0.01) in percent fat at 10 d WT. Carcass weights and yields were improved with ZH feeding and may continue to improve even up to 10 d after withdrawal of the supplement. Tenderness was slightly reduced with ZH supplementation but was unaffected by WT. Zilpaterol hydrochloride can be a valuable supplement to finishing beef steers to improve carcass lean yields and composition.

Top sirloin butt steaks were used to determine the effects on color stability of supplementing zilpaterol hydrochloride (ZH) to beef and calf-fed Holstein steers. This study compared the effects of dietary ZH supplementation for 0, 20, 30, or 40 d on feed. One-half of the top sirloin butts were enhanced and packaged in modified-atmosphere packaging (MAP); the remaining one-half were packaged in polyvinylchloride (PVC) film. Beef steaks packaged with PVC from cattle supplemented for 30 d had a tendency (P = 0.07) to produce a redder (a* = 18.31) steak than the control cattle (a* = 17.00) or cattle supplemented for 40 d (a* = 17.05). In beef steaks, ZH had no effect on subjective visual color (P = 0.15 to 0.27) and discoloration (P = 0.10 to 0.59) of steaks packaged with PVC when stratified by day of display, with the exception of visual color on d 5. Beef steaks under MAP from cattle supplemented for 20 d were redder (a* = 19.50, P < 0.05) than those from cattle supplemented for 30 (a* = 18.07) or 40 d (a* = 17.57), but were similar to the control steaks (a* = 18.68). There was no effect (P > 0.05) of retail display day and day of supplementation on objective or subjective color of calf-fed Holstein steaks packaged with PVC. Dietary supplementation for 20 d produced a greater (P < 0.05) b* value on d 1 of display in MAP-packaged steaks from calf-fed Holsteins. If recommending a period of dietary supplementation, 20 to 30 d would be suggested to result in, on average, the brightest, reddest sirloin butt steaks.

The objective of these studies was to evaluate the effects of zilpaterol hydrochloride (ZH), fed for 0, 20, or 30 d, on meat quality attributes of calf-fed Holstein steers. Steers were slaughtered at a commercial facility, and carcasses were selected by HCW to represent the pen mean. Further carcass selection was based on quality grade (Choice and Select) and yield grade. Proximate composition, measures of water holding capacity, and tenderness using Warner-Bratzler shear force after 7, 14, or 21 d postmortem were evaluated on the shoulder clod (triceps brachii), top butt (gluteus medius), and strip loin (longissimus lumborum). Percentage of purge for the 3 subprimals was not different (P > 0.05) among ZH treatments. Steers fed ZH for 20 d or 30 d had decreased (P < 0.05) percentages of fat in the triceps brachii, compared with 0-d ZH. Percentage of fat was less (P < 0.05) in the gluteus medius and longissimus lumborum when steers were fed ZH for 30 d compared with those steers fed ZH for 0 d. Percentage of fat was greater in Choice triceps brachii (P < 0.05) and longissimus lumborum (P < 0.10) compared with Select. Thaw loss was not different (P > 0.05) for any muscle due to ZH treatment. Only longissimus had a greater (P < 0.05) cooking loss with ZH treatment. Cooking loss was not different (P > 0.05) for the gluteus medius or longissimus lumborum due to quality grade or aging day. At each aging day, the 20- and 30-d ZH longissimus lumborum had greater (P < 0.05) shear force values than 0 d; however, 20- and 30-d ZH had a greater absolute change in shear force from 7 to 21 d than that of 0 d ZH. Triceps brachii steaks were less tender (P < 0.05) after ZH treatment, but gluteus medius steaks were not different (P > 0.05). There was no difference (P > 0.05) in shear force due to quality grade. Results illustrate the use of ZH in calf-fed Holstein steers will have minimal effects on purge, thaw, or cooking loss. Percentage of intramuscular fat will decrease, especially when fed for longer durations. Steaks from ZH treated steers were tougher than steaks from control animals at all aging times, but ZH steaks became more tender with postmortem aging.

To determine the effects of feeding zilpaterol hydrochloride (ZH) for 0, 20, 30, or 40 d (ZH0, ZH20, ZH30, ZH40) on semimembranosus (SM) steak color and color stability in 3 packaging systems, SM subprimals were removed from 60 calf-fed Holstein steers 24 h postmortem. A 7.62-cm-thick portion was removed from each subprimal and stored (2 degrees C) for 21 d; then two 2.54-cm-thick steaks were cut, overwrapped with polyvinyl chloride (PVC) film, and assigned to 0 or 3 d of display. Remaining portions of the subprimals were vacuum packaged for 10 d and then enhanced (10% with a solution containing 0.3% sodium chloride, 0.35% phosphate, and 0.05% rosemary extract), cut into steaks, packaged in high-oxygen (HO-MAP) or carbon monoxide (CO-MAP) modified atmosphere packaging (MAP), and assigned to 0, 3, or 5 d (HO-MAP) or 0 or 9 d (CO-MAP) of display. Panelists evaluated the deep and superficial portions of SM steaks for initial color, display color, discoloration, pH, L*, a*, b*, hue angle, and saturation indices. Feeding duration did not affect (P > 0.05) initial color scores of steaks in PVC. Steaks displayed in PVC from ZH20 or ZH30 diets were slightly brighter and less discolored than the ZH40 treatment. For enhanced steaks in HO-MAP, ZH20 steaks were darker on d 5 (P < 0.05) and more discolored (P < 0.05) on d 3 through 5 than all other diet treatments. For enhanced steaks from steers fed ZH40 and in CO-MAP, the deep and superficial SM tended (P > 0.05) to have improved display color compared with other dietary regimens; however, steaks in CO-MAP from all feeding durations had less than 20% metmyoglobin through d 9 of display. Overall, feeding ZH20 might result in steaks with slightly less color stability when packaged in HO-MAP; however, feeding ZH20 or ZH30 to calf-fed Holstein steers will yield steaks that have equal to or more desirable color traits when packaged in PVC or CO-MAP. Regardless of ZH feeding regimen, HO-MAP and CO-MAP extended the color life of the SM. The CO-MAP system minimized color differences between the superficial and deep portions of the SM muscle and extended total case life compared with traditional and HO-MAP packaging.

The need to provide consumer data for beef steak tenderness, juiciness, flavor, and overall palatability ratings from zilpaterol hydrochloride (ZH) beef to the processor, retailers, restaurants, and consumers is paramount. Consumer palatability responses were studied for 14- and 21-d aged USDA Choice and USDA Select quality grade beef and USDA Choice calf-fed Holstein New York Strip steaks from cattle that had been fed ZH for 0, 20, and 30 d before slaughter. Strip loins were cut into 2.54-cm-thick New York strip steaks and assigned to a 14- or 21-d aging treatment. The first and fourth steaks were assigned for 14- or 21-d WBSF analysis, and the second, third, fifth, and sixth steaks were reserved for consumer sensory panel evaluation. Warner-Bratzler shear force (WBSF) analysis was conducted at Texas Tech University (TTU, Lubbock), Kansas State University (Manhattan), Oklahoma State University (Stillwater), and West Texas A&M University (Canyon) with values used to sort steaks for consumer evaluation. Slice shear force analysis was performed at TTU on available paired consumer steaks. Consumers (n = 3,007) in 4 metropolitan areas (Baltimore, MD/Washington, DC; Chicago, IL; Los Angeles, CA; and Lubbock, TX) were asked to rate tenderness, juiciness, flavor, and overall acceptability. Consumers were selected to represent a wide range of income, education, and ethnicity at each city. Steaks were cooked to a medium degree of doneness (71 degrees C), cut into 1 cm(3) pieces, and served warm to consumers. Consumers tasted samples from each of 3 separate steaks from each ZH treatment (0, 20, and 30 d) and within each USDA quality grade and within the 14- and 21-d aging treatments. Steaks were selected to represent the distribution of tenderness for the first, second, and third SD either side of the mean for each treatment. A second calf-fed Holstein consumer study (n = 240) was conducted with consumers eating USDA Choice 14- and 21-d aged steaks from Holstein cattle fed ZH for 0 or 20 d. Steaks from 0- and 20-d ZH treatments were different for tenderness for the 14-d aged USDA Choice and the calf-fed Holstein study groups. No differences were shown for all other 0- and 20-d ZH treatments for tenderness. The 21-d aged USDA Select steaks were improved with aging, which aided in removing the effects of ZH treatment. The ZH treatment of 30 d before slaughter resulted in increased WBSF values and decreased consumer tenderness, juiciness, and overall palatability ratings for 14-d-aged USDA Choice. No differences were shown for tenderness, juiciness, flavor, and overall palatability consumer ratings for 0- and 20-d steaks from 21-d Choice and 14- and 21-d Select quality and aging periods. Overall, USDA Choice Holstein steaks aged 14 and 21 d had differences in tenderness with ZH.

Our objective was to determine the effects of feeding zilpaterol hydrochloride (ZH), a beta-agonist, for the final 30 d of the feeding period, with or without a terminal estrogen + trenbolone acetate (TBA) implant (Revalor-S; 24 mg of estradiol-17beta and 120 mg of TBA; REV) on meat tenderness and carcass cutout yields. Crossbred steers (n = 2,279) were divided into 6 BW blocks and 24 pens. Within each block, pens were assigned randomly to 1 of 4 treatments: 1) no terminal implant (control); 2) a terminal REV given 91 d before slaughter; 3) no terminal implant plus ZH; and 4) a terminal REV implant plus ZH (REV+ZH). All cattle received Component TE-IS (16 mg of estradiol and 80 mg of TBA) on d - 61 of the feeding period [corrected]. Zilpaterol hydrochloride was added to the diets at a concentration of 8.38 mg/kg (DM basis) during the final 30 d of the feeding period, followed by a 3-d period before slaughter in which ZH was withdrawn from the diet. Carcasses (n = 30/treatment) were selected from the 2,279 cattle and fabricated into subprimal cuts as per Institutional Meat Purchase Specifications. Strip loins were collected, cut into 2.54-cm steaks, and aged 7, 14, and 21 d, after which Warner-Bratzler shear force (WBSF), collagen content, desmin degradation, and muscle fiber diameter measurements were determined. Feeding ZH increased (P < 0.05) yield of the #112A ribeye roll, #116B chuck mock tender, #167A peeled knuckle, #169 top inside round, #171B outside round, #171C eye of round, #180 strip loin, #184 top sirloin butt, and #189A full tenderloin for ZH treatment. Longissimus muscle WBSF at 7, 14, and 21 d postmortem was increased (P < 0.001) with ZH supplementation. Desmin degradation at 7, 14, and 21 d postmortem was not affected with REV or ZH supplementation compared with controls. Zilpaterol hydrochloride had an additive effect with REV on increasing LM fiber diameter (P < 0.001). When fed to cattle that received a terminal implant of REV, ZH potentially increased LM WBSF as a result of induced muscle hypertrophy. During the 21-d aging period, WBSF decreased with aging, suggesting that carcasses from cattle supplemented with ZH might require longer aging time to ensure that acceptable levels of tenderness are reached.

The objective of this research was to determine the effects of feeding zilpaterol hydrochloride (ZH) for 0, 20, 30, or 40 d before slaughter (ZH0, ZH20, ZH30, or ZH40, respectively) on semimembranosus (SM) color development and stability. A 7.62-cm-thick portion was removed from 60 beef steer SM subprimals and stored (2 degrees C) for 21 d; then two 2.54-cm-thick steaks were cut, overwrapped with polyvinyl chloride (PVC) film, and assigned to 0 or 3 d of display. Remaining portions of the subprimals were stored in a vacuum for 10 d and then enhanced 10% to a meat concentration of 0.3% sodium chloride, 0.35% phosphate, and 0.05% rosemary extract. Steaks were packaged in a high-oxygen (HO-MAP) or carbon monoxide (CO-MAP) modified atmosphere and assigned to 0, 3, or 5 d (HO-MAP) or 0 or 9 d (CO-MAP) of display. The deep (DSM) and superficial (SSM) portions of steaks were evaluated for initial color, display color, discoloration, pH, L*, a*, b*, hue angle, and saturation indices. For steaks in PVC, no differences (P > 0.05) occurred in initial or discoloration color scores because of ZH feeding duration. The enhanced SSM steaks from ZH20 in PVC were brighter red (P < 0.05) than SSM steaks from ZH40 in PVC. The DSM in PVC had less (P < 0.05) pH and paler (P < 0.05) color than the SSM. Display color scores for the DSM of PVC steaks were brighter red (P < 0.05) than the SSM initially (d 0 and 1), but the DSM discolored faster (P < 0.05) than the SSM on d 1 to 3. The SM steaks from steers fed ZH20 or ZH30 were slightly brighter and less discolored during display in PVC than the ZH40 diet. For enhanced steaks in HO-MAP, the DSM of ZH20 and ZH30 diets displayed 4 d and the DSM of ZH20 displayed 5 d was a brighter (P < 0.05) red than the DSM from ZH40. At display d 1 and 5, the SSM of ZH20 steaks in HO-MAP was a brighter (P < 0.05) red than SSM steaks from ZH40. The SSM of ZH40 HO-MAP steaks was darker (P < 0.05) red on d 3 than the SSM from other diets. For enhanced steaks in CO-MAP, ZH30 steaks were brighter (P < 0.05) red than ZH0 or ZH40 steaks on d 0 and 9 of display. Steaks in CO-MAP from all feeding durations were less than 20% discolored through d 9. The DSM was lighter (P < 0.05) than the SSM on d 0 for steaks packaged in HO-MAP and CO-MAP. Feeding cattle ZH for 20 or 30 d will yield steaks with color characteristics equal to or better than steaks from control cattle, whereas feeding ZH for 40 d will likely produce less desirable meat color traits.

An experiment was conducted using 200 beef carcasses to evaluate the effects of feeding zilpaterol hydrochloride with or without monensin and tylosin on carcass cutability and meat sensory variables. The experiment was conducted using a randomized complete block design with treatments arranged as a 2 (no zilpaterol vs. zilpaterol) x 2 (monensin and tylosin withdrawn vs. monensin and tylosin fed) factorial. Cattle (n=3,757) were fed zilpaterol hydrochloride, a beta(2)-adrenergic agonist, for 30 d at the end of the finishing period and withdrawn from zilpaterol hydrochloride for the last 5 d on feed. Five carcasses (weighing between 305 and 421 kg and free of slaughter defects) were selected from each of 40 feedlot treatment pens. Strip loins from the left sides were collected for sensory analysis and Warner-Bratzler shear force (WBSF) testing, and the rib was collected for 9th, 10th, 11th-rib dissections. A subsample of 3 carcass right sides per pen was fabricated into boneless subprimals according to Institutional Meat Purchase Specifications. Carcasses from zilpaterol-fed steers had greater (P or= 0.26). For the main effect of monensin and tylosin, withdrawal of monensin and tylosin decreased (P=0.01) consumer juiciness scores, although other yield and compositional measurements were not affected (P >or= 0.07). Zilpaterol is a strong repartitioning agent that increases meat yield through increased protein and decreased fat deposition.