No abstract

The objective of this study was to identify muscles from cow populations that are equivalent or may possibly be made equivalent to muscles from A-maturity, Select-grade cattle in terms of chemical, compositional, and color characteristics. Objective color, expressible moisture, proximate composition, pH, heme iron concentration, and total collagen content were determined for 9 muscles (M. gluteus medius, M. infraspinatus, M. longissimus dorsi, M. psoas major, M. rectus femoris, M. tensor fascia latae, M. teres major, M. triceps brachii lateral-head, and M. triceps brachii long-head) from 15 cattle from each of 5 commercially identified populations [fed beef cows (B-F), non-fed beef cows (B-NF), fed dairy cows (D-F), non-fed dairy cows (D-NF), and A-maturity, Select-grade cattle (SEL)]. Muscles from B-F and B-NF populations were more similar to the SEL than were the D-F and D-NF. There were 2 muscles, the M. infraspinatus and M. teres major, from the population of B-F that were similar, physically and chemically, to SEL in most traits. The majority of the 9 muscles from the cows did not differ (P < 0.05) from SEL for percentage expressible moisture, proximate composition, and total collagen content. However, notable differences in pH, objective color L*, total pigment content, and heme iron content existed between cow populations and SEL. The muscles from SEL had significantly (P < 0.05) lower total pigment and heme iron concentrations. These differences likely relate to the visual appearance of muscles from the different populations of cattle. Two of the 9 muscles studied were similar among cow populations and A-maturity, Select-grade beef.

Zilpaterol hydrochloride (ZH) is a β-adrenergic agonist approved to be fed at a rate of 8.3 mg/kg (100% DM basis) during the final 20 to 40 d of the finishing period in beef cattle followed by a mini­ mum 3-d withdrawal period antemortem. The Federal Drug Administration (FDA) approved label claims of increased rate of BW gain, improved feed efficiency, and increased carcass leanness. Before the release of ZH for commercial use in 2007, approximately 10 in­ dependent research trials at various universities and commercial feedlots were initiated. Articles in recent issues of the Journal of Animal Science are a result of the large comprehensive body of research designed to increase the understanding of the effect of ZH on beef cattle growth, carcass traits, and beef quality. The feed­ ing of ZH for 20 to 40 d with a 3-d withdrawal resulted in significantly increased ADG. The increases equate to an average of 9 kg heavier BW in ZH-fed steers. Hot carcass weight has been shown to increase to a larger degree compared with BW, with an average improve­ ment of 15 kg. Dressing percent is increased by 1.5 to 2.0% with the feeding of ZH. Increases in carcass lean­ ness were reported for cattle fed ZH mainly through a reduction in yield grades. The LM area was increased, along with yield of subprimal cuts from the round, flank, and loin. Warner-Bratzler shear force studies have shown LM steaks from ZH-treated cattle to have increased shear force values of 1.1 to 1.7 kg for 7-d-aged steaks, 0.4 to 1.3 kg for 14-d-aged steaks, and 0.27 to 1.4 kg for 21-d-aged steaks compared with controls. Re­ cent research has suggested that the aging response is normal in ZH steaks. Consumers were able to identify tenderness differences in 14-d-aged Choice steaks from cattle fed ZH for 20 d compared with 14-d-aged steaks from control cattle; this difference was mitigated with 21 d of postmortem aging. Zilpaterol hydrochloride has been shown to increase cattle growth and efficiency as well as lean tissue deposition in the carcass, with some impact on carcass traits such as Warner-Bratzler shear force.

The objective of this study was to quantify the effects of zilpaterol hydrochloride (ZH) on feeding performance and fabrication yield of concentrate-finished cull cows. Three hundred twenty commercial cull cows (2 to 10 yr old) were obtained from ranches in Missouri and South Dakota and assigned to 1 of 2 treatments: 1) a control diet containing no ZH and 2) a diet that contained ZH. Cows were fed for 75, 88, or 110 d, and all received the control ration until ZH treatments were initiated. Twenty-four days before slaughter, ZH feeding began for the designated treatment pens; cows were fed ZH [8.33 mg/kg (100% DM basis)] for 20 d with a 4-d withdrawal period before slaughter. No differences (P>0.05) were detected between the 2 treatment groups for initial BW or DMI. Final BW (640.5 vs. 619.1 kg), ADG for the last 24 d (2.75 vs. 2.17 kg), and G:F for the last 24 d (0.160 vs. 0.126) were greater (P<0.01) in cows fed ZH than the control cows. No differences (P > 0.05) were found for lean or skeletal maturity score, fat thickness, LM area, HCW, or calculated yield grade among the 2 treatment groups. Feeding ZH increased (P<0.01) HCW (390.1 vs. 369.2 kg), dressed carcass yield (61.01 vs. 59.45%), and LM area (93.3 vs. 86.5 cm(2)) and decreased (P<0.01) marbling score (Slight(63) vs. Slight(86)) compared with control cows. Cows fed ZH had greater (P<0.05) primal weights for chuck (mock) tender (2.63 vs. 2.28 kg), lip-on rib eye roll (13.54 vs. 12.56 kg), top sirloin butt (12.74 vs. 11.82 kg), top (inside) round (14.58 vs. 12.89 kg), and peeled knuckle (12.87 vs. 11.51 kg) while yielding a decreased percentage of mechanical knife trimmings (1.15 vs. 1.35%; P<0.01) and more top (inside) rounds (3.71 vs. 3.46%; P=0.02) than the control cows. No differences (P>0.07) were found for the remaining fabrication yield attributes. The ZH-treated cows had greater (P<0.05) fabrication dollar values for chuck (mock) tender (8.82 vs. 7.66 $/carcass), lip-on rib eye roll (64.20 vs. 59.56 $/carcass), strip loin (0 × 1; 49.13 vs. 44.75 $/carcass), top sirloin butt (35.60 vs. 33.01 $/carcass), bottom round (flat; 44.23 vs. 39.23 $/carcass), top (inside) round (60.30 vs. 53.33 $/carcass), knuckle (peeled; 44.26 vs. 39.57 $/carcass), and total salable yield (879.50 vs. 803.70 $/carcass) than control cows. These results suggest the feeding of ZH to concentrate-finished cull cows enhances production efficiencies and can add new value to the cull cow market.

Retail cutting tests were conducted on subprimals from cattle fed zilpaterol hydrochloride (ZH) to determine if the improved carcass composition and red meat yield resulting from ZH feeding would translate into increased retail yields of ready-to-cook products. As part of a 3-phase study, selection of carcasses from Holstein steers was done once (fall 2008), followed by the collection of carcasses from beef-type steers on 2 separate occasions (beef study I: summer 2009; beef study II: spring 2010). Each of the 3 groups of steers was assigned previously to 1 of 2 treatments, treated (fed 8.3 mg/kg of ZH for 20 d) or control (not fed ZH). All steers were slaughtered and carcasses were fabricated in commercial beef-processing establishments. Only those carcasses grading USDA Choice or higher were used. Five subprimals were used for both the calf-fed Holstein study (n = 546 subprimals) and beef study I (n = 576 subprimals): beef chuck, chuck roll; beef chuck, shoulder clod; beef round, sirloin tip (knuckle), peeled; beef round, top round; and beef round, outside round (flat). Seven subprimals were used in beef study II (n = 138 subprimals): beef chuck, chuck roll; beef round, sirloin tip (knuckle), peeled; beef round, top round; beef round, eye of round; beef loin, strip loin, boneless; beef loin, top sirloin butt, boneless; and beef loin, tenderloin. A simulated retail market environment was created, and 3 retail meat merchandisers prepared retail cuts from each subprimal so salable yields and processing times could be obtained. Differences in salable yields were found for the calf-fed Holstein steer chuck rolls (96.54% for ZH vs. 95.71% for control; P = 0.0045) and calf-fed Holstein steer top rounds (91.30% for ZH vs. 90.18% for control; P = 0.0469). However, other than heavier subprimals and an increased number of retail cuts obtained, total salable yields measured on a percentage basis and processing times were mostly unaffected by ZH. Cutability advantages of feeding ZH are achieved primarily in the carcass-to-subprimal conversion rather than in the subprimal-to-retail conversion.

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.

Beef knuckles (n = 60) were chosen from a population of 328 knuckles to test a selection procedure and determine the potential causes of liver-like off-flavor. In phase I, 2 independent panelists were allowed to smell the aromas or smell and taste samples of cooked beef to determine the presence or absence of the liver-like off-flavor and off-flavor intensity. The panelists tested knuckles from 5 feedlots, but only identified 29 as having an off-flavor. A kappa statistic was generated to assess the level of agreement of the 2 panelists that indicated the panelists moderately or substantially agreed when judgments were based on smell exclusively or smelling and tasting, respectively. Although the agreement was acceptable (κ = 0.57 and 0.76), there was not enough variation in the liver-like

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 < 0.01) than those from steers fed CON or RH, which were similar. An interaction between βAA and aging was observed (P < 0.01) for WBSF but not SSF. Within steaks aged 14 d, ZH steaks required the most force to shear, RH steaks were intermediate, and CON steaks had the lowest WBSF values; however, RH steaks had a stronger response to aging than CON or ZH steaks, resulting in the lowest WBSF values at 21 d. Slice shear force values were greater (P < 0.01) in steaks from steers fed ZH than in steaks from steers fed CON or RH, which did not differ. Following shear force analyses, steaks within 2 SD of each treatment mean for WBSF were selected randomly for consumer assessment of eating quality. Consumer testing (n = 400; 200/postmortem aging period) was arranged in a 3 × 3 factorial representing 3 quality grades (Select, Low Choice, and Premium Choice) and 3 treatments (ZH, RH, and CON). In steaks aged 14 d, βAA supplementation affected (P < 0.01) tenderness, flavor, and overall liking and tenderness acceptability, resulting in lower consumer scores for ZH than CON and RH; however, juiciness, flavor, and overall acceptability were similar (P > 0.05). In steaks aged 21 d, feeding βAA influenced (P < 0.01) only tenderness and juiciness scores. Despite these differences, βAA did not affect (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.