Feeding Zilpaterol Hydrochloride Research Articles

Mineral composition of serially slaughtered Holstein steers supplemented with zilpaterol hydrochloride.

Calf-fed Holstein steers (n = 115; 449 ± 20 kg) were utilized in a serial harvest experiment. A baseline group of five steers was harvested after 226 d on feed (DOF), which was designated day 0. The remaining cattle were assigned randomly to 11 harvest groups, with slaughter every 28 d. Cattle were either not (CON) or were fed zilpaterol hydrochloride for 20 d followed by a 3 d withdrawal (ZH). There were five steers per treatment in each slaughter group ranging from days 28 to 308. Whole carcasses were divided into lean, bone, internal cavity, hide, and fat trim components. Apparent mineral retention (Ca, P, Mg, K, and S) within the body was calculated as the difference between mineral concentration at slaughter and day 0. Mineral concentration at day 0 was determined from body composition of steers harvested at day 0 multiplied by individual live body weight (BW) at day 0. All data were analyzed as a 2 × 11 factorial arrangement with individual animal as the experimental unit. Orthogonal contrasts were used to analyze linear and quadratic contrasts over time (11 slaughter dates). There were no differences in concentration of Ca, P, and Mg in bone tissue as feeding duration increased (P ≥ 0.89); concentration of K, Mg, and S in lean tissue did fluctuate across DOF (P < 0.01). Averaged across treatment and DOF, 99% of Ca, 92% of P, 78% of Mg, and 23% of S present in the body were in bone tissue; 67% of K and 49% of S were in lean tissue. Expressed as gram per day, apparent retention of all minerals decreased linearly across DOF (P < 0.01). Expressed relative to empty body weight (EBW) gain, apparent Ca, P, and K retention decreased linearly as BW increased (P < 0.01) whereas Mg and S increased linearly (P < 0.01). Apparent retention of Ca was greater for CON cattle (greater bone fraction) and apparent retention of K was greater for ZH cattle (greater muscle fraction) when expressed relative to EBW gain (P ≤ 0.02), demonstrating the increase in lean gain by ZH cattle. There were no differences in apparent retention of Ca, P, Mg, K, or S due to treatment (P ≥ 0.14) or time (P ≥ 0.11) when expressed relative to protein gain. Apparent retention averaged 14.4 g Ca, 7.5 g P, 0.45 g Mg, 1.3 g K, and 1.0 g S/100 g protein gain. Expressing apparent mineral retention on a protein gain basis minimized effects of rate and type of gain, allowing for better comparison across treatments and time. Feeding zilpaterol hydrochloride did not affect apparent mineral retention when expressed relative to protein gain.

Effects of duration of zilpaterol supplementation on growth-performance, dietary energetics, carcass characteristics, and meat quality of crossbred yearling heifers slaughtered at lighter, less-than-mature final body weight (460 kg)

Our objective was to examine the effects of duration of zilpaterol hydrochloride (ZH) supplementation on growth performance, estimated dietary energetics, carcass characteristics, and meat quality in crossbred yearling heifers when slaughtered at lighter, less-mature final weight. Treatments consisted of a finishing diet based on steam-flaked corn supplemented with (1) 0 ZH (negative control); (2) 0.15 mg of ZH/kg of live weight supplemented for 20 of the final 23 d of the finishing period; (3) 0.15 mg of ZH/kg of live weight supplemented for 25 of the final 28 d of the finishing period, or (4) 0.15 mg of ZH/kg of live weight supplemented for 30 of the final 33 d of the finishing period. Duration of ZH supplementation did not affect ( P ≥ 0.15) any of the variables measured. Compared with the control, ZH increased ( P ≤ 0.02) carcass-adjusted weight gain, G:F, and apparent dietary NE. Zilpaterol supplementation also increased ( P ≤ 0.05) hot carcass weight, carcass DP, and LM area without effects on USDA QG, fat thickness, or KPH fat. Zilpaterol supplementation increased ( P < 0.01) gross retail cuts by 3.6%, when adjusting to a constant carcass weight. There were no treatment effects ( P ≥ 0.11) on shear force or meat color. Zilpaterol hydrochloride supplementation in heifers slaughtered at a final weight that was less than was estimated to be mature (460 kg) improved growth performance, hot carcass weight, carcass DP, LM area, and retail cuts in a manner consistent with results of previous studies in which heifers were slaughtered at heavier (>550 kg) BW. Effects of ZH on meat quality was not significant. Reducing ZH feeding duration from 30 to 20 d may not adversely affect growth performance, carcass characteristics, and meat quality.

Meat Quality of Nellore Young Bulls-Effects of Different Days on Feed and Zilpaterol Hydrochloride Supplementation.

Simple Summaryβ-adrenergic agonists have been widely used to improve meat production efficiency and can be a valuable tool for increasing world meat supply. They act as nutrient repartitioning agents, increasing lean tissue deposition but negatively affecting meat quality, notably reducing palatability. While this metabolic modifier improves the growth performance of Zebu breeds, they can impair even more meat quality in feedlot-finished cattle. This study was developed to evaluate the impact of zilpaterol hydrochloride (ZH) feeding duration and time on feed (90 or 117 days), on meat quality, and on composition properties of meat from young Zebu bulls. Supplementing ZH resulted in a leaner and less tender and juicy meat compared to non-supplemented animals, with few differences in fatty acid composition. Feeding animals for 90 or 117 days had a small impact on meat quality attributes. Feeding ZH to Zebu bulls would require additional tenderization practices to reduce the negative effects of ZH on meat quality.Ninety-six Nellore young bulls were fed (90 or 117 day) diets containing ZH (8.33 mg/kg) for 0, 20, 30, or 40 days to evaluate the effects of days on feed (DOF) and length of zilpaterol hydrochloride (ZH) supplementation on meat quality. At the end of feeding period, animals were slaughtered, and samples of the Longissimus muscle were collected to evaluate the chemical composition, fatty acid profile, color stability, shear force, and sensory profile. DOF did not affect chemical composition, shear force, sensory tenderness, and most of fatty acids; however, animals fed for 90 d had lower redness (p < 0.01), sustained juiciness (p < 0.01), and more flavor (p = 0.03) than those fed for 117 d. The ZH supplementation decreased lipid content and redness (p < 0.01), initial and sustained tenderness (p < 0.01), initial and sustained juiciness (p < 0.01), but increased protein (p < 0.01) and shear force (p < 0.01) as compared to non-supplemented animals. The ZH supplementation increased total PUFA, c9,c12-18:2, and 20:4-n6, and decreased c9-20:1 (p < 0.05). Feeding ZH impairs meat quality attributes of Nellore young bulls, regardless of duration of supplementation, while DOF has a small effect on meat quality properties.

Muscle fiber morphometry and physicochemical characteristics of the Longissimus thoracis muscle of hair male lambs fed zilpaterol hydrochloride and implanted with steroids

Muscle fiber morphometry and physicochemical characteristics were evaluated in LT muscles obtained from entire male lambs treated with zilpaterol hydrochloride (ZH, 0 and 0.15 mg/kg body weight) and/or steroidal implant (SI, with and without trenbolone acetate/estradiol). ZH and SI acted synergistically to increase LT area, type-IIb fiber cross-sectional area and soluble collagen content, likewise to decrease metmyoglobin concentration and insoluble collagen content. Ash content and ultimate pH showed a decrease due to an antagonistic effect between ZH and SI. Content of total collagen, protein, fat, moisture, oxidized lipids and water-holding capacity were unaffected by ZH and SI. Supplemental ZH, but not SI, decreased all color parameters and tended to increase shear force. Overall, the SI implantation of male lambs followed by a ZH supplementation promoted greater LT hypertrophy, without affecting protein and fat content, and physicochemical characteristics in their meat.

PSVI-7 Effects of feeding chromium- and zinc- amino acid complexes on growth performance and carcass characteristics of finishing bulls fed zilpaterol hydrochloride for the last 30 days in the feedlot

Abstract A 2 x 2 factorial study was conducted to evaluate main and interaction effects of feeding amino acid complexed sources of Zn (Zn-AAC; 40 mg /kg DM from Availa® Zn; Zinpro Corp., Eden Prairie, MN) and Cr (chromium methionine; Cr-Met; 0.20 mg / kg DM from Availa® Cr; Zinpro Corp., Eden Prairie, MN) fed in combination or separately, compared to an iso-Zn level Control (CON) group that provided Zn from ZnSO4 (80 mg Zn∙kg-1DM) with no supplemental source of Cr. Treatments were replicated into 4 pens with 5 finishing Bos taurus x Bos indicus bullocks/pen (80 bullocks; BW= 421 kg). Treatment diets were initiated 28 d prior to starting zilpaterol hydrochloride (ZIL; 15 mg/kg BW) with ZIL fed daily for 33 d followed by a 4 d withdrawal before harvest. During the ZIL-feeding Zn-ACC x Cr-Met interactions were present for ADG and Gain:Feed (G:F) where Zn-ACC improved ADG (P≤ 0.05) and Cr-Met improved G:F vs. CON. Effects may have been mediated by differences in DM intake (DMI), where DMI was numerically increased by Zn-ACC and decreased (P ≤ 0.01) by Cr-Met. Overall, feeding Cr-Met moderated DMI and improved G:F (P ≤ 0.05). Measures of carcass composition were not affected by Zn-ACC or Cr-Met. Hot carcass weight was increased (P ≤ 0.05) by feeding Zn-ACC and tended to increase with Cr-Met. Daily carcass gain increased from feeding either Zn-ACC or Cr-Met during the ZIL phase and overall study. Feeding Zn-ACC was a primary driver during the ZIL period and overall trial for increasing growth rate, with little or no influence on DM intake while feeding Cr-Met moderated DM intake to improve dietary and energetic efficiency. Balancing the feeding levels of Zn-ACC and Cr-Met will be key to optimizing the overall biological response and net return.

Feedlot performance, carcass characteristics and meat quality of Nellore bulls and steers fed Zilpaterol hydrochloride

This study aimed to determine the effects of zilpaterol hydrochloride (ZH) on feedlot performance, carcass traits, feeding behavior and meat quality characteristics of Nellore steers and bulls. This study was conducted at the São Paulo State University (UNESP) feedlot, Botucatu Campus, Brazil. Seventy-two 18-month-old Nellore cattle from the same cattle herd, 36 steers and 36 bulls, were selected for this study. The experiment had a randomized block design based on the animals’ initial BW, in a 2 × 2 factorial arrangement of treatments, in which the factors were ZH addition to the diet (0 or 7.5 mg of ZH/ kg of feed 20 d prior to slaughter; ZILMAX® MSD Animal Health, São Paulo, SP, Brazil) and gender (bulls or steers). The 24 pens were considered the experimental units in this study, and each treatment was replicated six times (n = 3 per pen). Cattle were fed for 112 days, and the addition of 7.5 mg of ZH/ kg of feed was done for 20 d prior to slaughter (from day 90 to day 109). A withdrawal period of three days before slaughter was respected (from day 110 to 112). During the period of ZH supplementation, cattle fed ZH presented greater final BW (516.45 vs. 512.50 kg; P ≤ 0.001), ADG (1.73 vs. 1.32 kg; P ≤ 0.001), and improved G:F by 38.1% (0.187 vs. 0.135; P ≤ 0.001), when compared to cattle not fed ZH. Nellore steers receiving ZH reduced DMI by 9% when compared to steers not fed ZH (P = 0.04); however, Nellore bulls had similar intake regardless of ZH supplementation. Overall, cattle receiving ZH improved G:F by 6.6% (0.161 vs. 0.151; P = 0.03) and increased final LM area (79.32 vs. 76.30 cm2; P = 0.04), HCW (292.75 vs. 280.00 kg; P < 0.001), and dressing percentage (56.68 vs. 55.14; P < 0.001). The interaction between ZH supplementation and gender was observed (P = 0.02) for 12th rib fat daily gain in which steers decreased their rate of fat deposition when fed ZH, but no effect was observed for bulls. A significant increase was observed (4743.12 vs. 4286.23 µm2; P = 0.03) in the average area of Semitendinosus muscle fibers of cattle supplemented with ZH; however, no main effect of ZH supplementation was observed for final marbling (P = 0.27) or shear force (P = 0.20). Overall, ZH increased performance and hot carcass weight of Nellore cattle regardless of gender. In addition, supplementation of ZH lead to similar feedlot performance and meat quality between Nellore steers fed ZH and Nellore bulls not consuming ZH.

Daily optimal level of a generic beta-agonist based on zilpaterol hydrochloride for feedlot hair lambs

Two experiments were completed to determine the dietary optimal dose of a generic product (Grofactor®) of zilpaterol hydrochloride (ZH) in fattening male lambs. In experiment 1, 32 lambs were assigned to four daily doses of ZH (n = 8): 0 (Control), 0.10, 0.20, and 0.30 mg/kg of body weight (BW). In experiment 2, the doses of ZH with the best biological response from experiment 1 (i.e., 0.10 and 0.20 mg/kg of BW per lamb) were compared using 18 lambs (9 lambs per treatment), as well as a control group of 9 lambs. In experiment 1, growth rate, feed efficiency, hot (HCW) and cold (CCW) carcass weight and dressing percentage showed a quadratic increase (P ≤ 0.05) as the dose of ZH increased, but all these traits were similar among ZH-fed lambs. Yield of wholesale cuts was not impacted by ZH dose. Percentages of skin and foot decreased linearly (P ≤ 0.01) with increasing ZH dose. However, head, liver, and stomach had a quadratic effect (P ≤ 0.05) to increasing levels of ZH, with the lowest values at the intermediate ZH addition levels. In experiment 2, ZH-fed lambs compared with control had better (P ≤ 0.04) feedlot performance, HCW, CCW, dressing percentage, Longissimus dorsi muscle area and carcass length. Addition of ZH only increased (P ≤ 0.03) the leg yield using any of the doses. Feeding ZH decreased (P ≤ 0.03) the percentages of blood, liver, spleen, and stomach, while percentage of lungs increased (P < 0.01). In both experiments, ZH supplementation had no effect on fat thickness, and omental and mesenteric fat. We concluded that generic ZH is effective as growth promoter in male lambs finished in feedlot to a daily dosage of 0.10 mg/kg of BW.

The beta-adrenergic agonist zilpaterol hydrochloride may predispose feedlot cattle to cardiac remodeling and dysfunction

Background: The aim of this study was to address producer concerns that the β2-adrenergic agonist zilpaterol hydrochloride, a bovine growth promotant, predisposes cattle to cardiac disease and death. Our objectives were to evaluate the effect of zilpaterol on cardiac function, morphology, and risk of myocardial injury. Methods: A prospective, case-control study was conducted on one feedlot in northern Colorado using convenience sampling of Angus-based steers (n = 80). Pulmonary arterial pressures (mean, systolic, and diastolic) were measured. Plasma cardiac troponin I was measured in a sub-sample of steers that were followed to slaughter (n = 31). The carcass, left ventricle plus inter-ventricular septum, and right ventricle were weighed. Results: Relative to controls, steers fed zilpaterol hydrochloride had an adjusted left ventricle and septum that was 185 g heavier (95 % CI: 19, 350 g; P = 0.03), a diastolic pulmonary arterial pressure that was 10 mm Hg greater (95 % CI: 3, 17 mm Hg; P = 0.004), and a greater concentration of cardiac troponin I (P = 0.01), a biomarker of myocardial injury. Furthermore, left ventricular mass tended to be positively and deleteriously associated with diastolic pulmonary arterial pressure in steers fed zilpaterol (P = 0.08) but not controls (P = 0.28). Conclusions: Our findings suggest that zilpaterol hydrochloride induced sufficient left ventricular hypertrophy to cause impaired left ventricular relaxation or diastolic dysfunction and myocardial injury. In conclusion, these results support concerns that, in the feedlot studied, zilpaterol hydrochloride predisposes cattle to cardiac disease.

Interaction between supplemental zinc oxide and zilpaterol hydrochloride on growth performance, carcass traits, and blood metabolites in feedlot steers.

Interactive effects of supplemental Zn and zilpaterol hydrochloride (ZH) were evaluated in feedlot steers ( = 40; 652 kg ± 14 initial BW) to determine their impact on feedlot performance, blood constituents, and carcass traits. The study was conducted as a randomized complete block design with a 2 × 2 factorial treatment arrangement. Steers were blocked by BW and randomly assigned to treatments. Factors consisted of supplemental Zn (60 or 300 mg/kg diet DM) and ZH (0 or 8.33 mg/kg) in the diets. For diets supplemented with 300 mg Zn/kg DM, 60 mg Zn/kg was supplemented as zinc sulfate and 240 mg Zn/kg was supplemented as zinc oxide, and the diet was fed for 24 d. Zilpaterol hydrochloride was fed for 21 d followed by a 3-d withdrawal. Cattle were housed in partially covered individual feeding pens equipped with automatic waterers and fence-line feed bunks and were fed once daily for ad libitum intake. Plasma samples were collected on d 0 and 21 to assess changes in Zn, plasma urea nitrogen (PUN), glucose, and lactate concentrations, and serum samples were collected on d 21 to assess IGF-1 concentration. On d 25, cattle were weighed and transported 450 km to a commercial abattoir for harvest; HCW and incidence of liver abscesses were recorded. Carcass data were collected after 36 h of refrigeration. Data were analyzed as a mixed model with Zn, ZH, and Zn × ZH as fixed effects; block as a random effect; and steer as the experimental unit. No interaction or effects of Zn or ZH were observed for IGF-1 concentration, plasma glucose, or lactate concentrations ( ≥ 0.25). No interaction between Zn and ZH was observed for PUN concentration, but PUN decreased with ZH ( < 0.01). There were no effects of ZH or Zn on ADG, DMI, final BW, feed efficiency, HCW, back fat, KPH, quality grade, or incidence of liver abscesses ( > 0.05). Zinc supplementation tended ( = 0.08) to improve the proportion of carcasses grading USDA Choice. Feeding ZH decreased yield grade ( = 0.05) and tended to increase LM area ( = 0.07). In conclusion, increasing dietary concentrations of Zn does not impact response to ZH, but feeding ZH altered circulating concentrations of PUN.

Effects of zilpaterol hydrochloride on methane production, total body oxygen consumption, and blood metabolites in finishing beef steers.

An indirect calorimetry experiment was conducted to determine the effects of feeding zilpaterol hydrochloride (ZH) for 20 d on total body oxygen consumption, respiratory quotient, methane production, and blood metabolites in finishing beef steers. Sixteen Angus steers (initial BW = 555 ± 12.7 kg) were individually fed at ad libitum intake and used in a completely randomized design. The model included the fixed effects of dietary treatment, day, and treatment × day. Dry matter intake did not differ between the treatments ( = 0.89), but was greater on d 0 than any other day ( < 0.01). Oxygen consumption was not different between treatments ( = 0.79), but was different across day ( < 0.01) on d 7, 14, 21, and 28. Respiratory quotient was less for cattle fed ZH than control ( < 0.01), and also different across day ( < 0.01), being greater on d 7, 21, and 28 than d 3 or 21. Methane production (L/kg of DMI) was greater for steers fed the control vs. the ZH diet ( < 0.01), and it also differed by day ( < 0.01), being greater on d 21 and 28 than d 0, 3, 7, and 14. Nonesterified fatty acids were not different across treatments ( = 0.82), and there was no effect of treatment on β-hydroxybutyrate concentration ( = 0.45). Whole blood glucose concentrations were not affected by feeding ZH in this experiment ( = 0.76); however, lactate concentrations were reduced by feeding ZH ( = 0.03). Additionally, there was no treatment effect on ɑ-amino-N, blood glutamate, or glutamine ( ≥ 0.16). Plasma NH was not affected by ZH ( = 0.07), but plasma urea nitrogen was reduced by ZH ( < 0.01). Urinary creatinine was increased by steers receiving ZH ( = 0.01), and urine 3-methylhistidine (3-MH) concentrations were normalized to creatinine, the 3-MH:creatinine ratio decreased from d 0 to d 3 in steers fed ZH, and remained less than control steers until d 28. These data provide insight into how β-agonists alter nutrient partitioning and improve the efficiency of tissue accretion, mainly through decreased muscle protein turnover and altering the catabolic fuel for peripheral tissues.

Fabrication yields of serially harvested calf-fed Holstein steers fed zilpaterol hydrochloride1

Holstein steers ( = 110) were fed zilpaterol hydrochloride (ZH) for 0 or 20 d before slaughter during a 280-d serial harvest study. Cattle were harvested every 28 d beginning at 254 d on feed (DOF) and concluding at 534 DOF. After slaughter, carcasses were chilled for 48 h and then fabricated into boneless closely trimmed or denuded subprimals, lean trim, trimmable fat, and bone. Inclusion of ZH increased cold side weight (CSW) by 10.3 kg ( < 0.01; 212.7 vs. 202.4 kg [SEM 1.96]) and saleable yield by 10.4 kg ( < 0.01; 131.9 vs. 121.5 kg [SEM 1.16]) in calf-fed Holstein steer carcasses. Additionally, saleable yield as a percentage of CSW increased ( ≤ 0.01) by 2.19% (62.64 vs. 60.45% [SEM 0.22]) for cattle supplemented with ZH. Subprimal weights were heavier ( ≤ 0.05) from cattle that received ZH except for the bottom sirloin ball tip, back ribs, and outside skirt regardless of slaughter endpoint. Yield of top round, bottom round, and knuckle was increased ( ≤ 0.01) following ZH supplementation by 0.37, 0.24, and 0.18%, respectively. Yield of the top sirloin butt, strip loin, and tenderloin was increased ( ≤ 0.01) concurrent with ZH supplementation by 0.18, 0.11, and 0.09%, respectively. Regarding the rib primal, the rib eye roll tended ( = 0.08) to had increased yield (2.80 vs. 2.72% [SEM 0.03]) with ZH supplementation; both back ribs and blade meat exhibited increased ( ≤ 0.04) yields of 0.04%. Relative to the chuck primal, increased ( ≤ 0.03) yields of shoulder clod, pectoral meat, and mock tender were observed (0.13, 0.07, and 0.04%, respectively). Yield changes for subprimal brisket, plate, and flank were limited to increased ( < 0.01) proportion of flank steak and elephant ear (cutaneous trunci), 0.07 and 0.04%, respectively. Feeding duration notably altered ( ≤ 0.01) weights and percentages of all subprimals except the brisket. Saleable yield increased ( ≤ 0.01) by 0.192 kg/d with additional DOF. Moreover, trimmable fat and bone increased ( ≤ 0.01) by 0.146 and 0.050 kg/d, respectively. These data illustrate improved saleable meat yields for calf-fed Holstein steers supplemented with ZH and provide the beef industry knowledge of fabrication yield changes throughout a wide range of harvest endpoints.

Fabrication yields of serially harvested calf-fed Holstein steers fed zilpaterol hydrochloride

Fabrication yields of serially harvested calf-fed Holstein steers fed zilpaterol hydrochloride

Carcass grading characteristics of serially harvested calf-fed Holstein steers fed zilpaterol hydrochloride.

Serial harvests were conducted using Holstein steers ( = 110) fed zilpaterol hydrochloride (ZH) for 0 or 20 d prior to harvest. Steers were harvested in 28-d increments beginning at 254 d on feed (DOF) and ending at 534 DOF. After harvest and a 36-h chill period, carcasses were evaluated using grading methods standard for the United States (USDA), Canada (Canadian Beef Grading Association [CBGA]), and Japan (Japanese Meat Grading Agency [JMGA]). No ZH treatment differences ( = 0.81) were detected for 12th-rib fat thickness; however, additional DOF resulted in a daily linear increase ( < 0.01) of 12th-rib fat thickness by 0.004 cm/d. Longissimus muscle area was increased ( < 0.01) by 8.7 cm with ZH supplementation and linearly increased ( < 0.01) 0.08 cm2/d with additional DOF. Calculated USDA yield grade (YG) decreased ( < 0.01) 0.33 units due to ZH treatment and linearly increased ( < 0.01) 0.009 units/d. Steers supplemented with ZH exhibited increased ( < 0.01) CGBA LM width; however, no difference ( = 0.37) was detected in CGBA LM length. No ZH treatment differences ( = 0.64) were observed for CBGA fat class; however, CGBA fat class linearly increased ( < 0.01) by 0.01 units/d. No ZH differences ( ≥ 0.17) were detected for the CBGA estimated lean percentage or YG equations. Evaluation for JMGA occurs at the sixth and seventh rib interface; LM area was 4.6 cm2 greater ( = 0.02) for cattle supplemented with ZH and linearly increased ( < 0.01) by 0.07 cm2/d with additional DOF. Subcutaneous fat thickness was not different among ZH treatments ( = 0.10) but linearly ( < 0.04) increased ( < 0.01) by 0.005 cm/d with additional DOF using the JMGA grading method. No difference ( ≥ 0.21) was calculated between ZH treatments or DOF for JMGA estimated yield. No ZH treatment differences ( = 0.85) were detected in USDA marbling score; however, marbling linearly increased ( < 0.01) 0.07 units/d. These data illustrate the impact of ZH and increasing DOF on economically important carcass grading outcomes used in the USDA, CBGA, and JMGA grading programs.

1544 Influence of supplementary zinc- and chromium–amino acid complexes on growth performance and carcass characteristics of finishing cattle fed zilpaterol hydrochloride

1544 Influence of supplementary zinc- and chromium–amino acid complexes on growth performance and carcass characteristics of finishing cattle fed zilpaterol hydrochloride

Effect of vitamin D, zilpaterol hydrochloride supplementation, and postmortem aging on shear force measurements of three muscles in finishing beef steers.

Vitamin D (D3) supplementation may be used to increase tenderness in beef from cattle fed zilpaterol hydrochloride (ZH). The study was arranged as a 2 × 2 factorial with fixed effects of ZH (no ZH or ZH fed at 8.3 mg/kg DM for 20 d with a 3-d withdrawal) and D3 (no D3 or 500,000 IU D3·steer·d for 10 d prior to harvest). Cattle ( = 466) were harvested in 2 blocks on the basis of BW with subsequent collection of carcass data. Full loins and inside rounds ( = 144 of each subprimal) were collected for fabrication of 5 steaks from the longissimus lumborum (LL), gluteus medius (GM), and semimembranosus (SM), which were aged for 7, 14, 21, 28, or 35 d. Warner-Bratzler shear force (WBSF) was used to evaluate mechanical tenderness of LL, GM, and SM steaks at all aging periods. Slice shear force (SSF) analysis was conducted on only 14- and 21-d LL steaks. No interactions ( > 0.05) between ZH and D3 occurred throughout the entire study. Supplementing ZH resulted in increased HCW ( < 0.01), larger LM area ( < 0.01), and improved calculated yield grades ( < 0.01) with decreases in fat thickness ( = 0.02) and marbling scores ( = 0.05). Supplementation with D3 increased calculated yield grade ( < 0.01) and decreased ( = 0.01) rib eye area. Feeding ZH increased ( ≤ 0.05) WBSF of LL steaks at each postmortem age interval, whereas D3 had no effect ( > 0.05) on WBSF or SSF of LL steaks. Like for WBSF, ZH supplementation increased SSF values at 14 and 21 d postmortem ( < 0.01) compared with those for non-ZH steaks. There was an interaction between ZH and postmortem age ( < 0.01) for WBSF of LL steaks. At 7 d LL steaks from ZH steers sheared over 0.6 kg greater than non-ZH steaks; however, by 21 d this difference was reduced to an average of 0.2 kg. Differences in distribution between LL steaks below 3.0 kg from non-ZH and ZH-fed cattle were also notable ( ≤ 0.05) through 21 d of aging. At 35 d postmortem a high proportion of LL steaks (68.5%) from ZH-fed steers required less than 3.0 kg to shear. Supplementation with ZH and D3 had no impact ( > 0.05) on WBSF values of GM steaks. Feeding ZH did not alter WBSF of SM steaks, but at 28 d D3 increased ( = 0.04) WBSF values. Shear force in ZH steaks was not effectively reduced by feeding D3 for 10 d to steers prior to harvest. Aging, however, was an effective method of reducing initially greater shear force values in LL steaks and, to a lesser degree, GM steaks from ZH-fed cattle.

Effects of shade and feeding zilpaterol hydrochloride to finishing steers on performance, carcass quality, heat stress, mobility, and body temperature.

Steers ( = 480; 22% with black hides and 78% with red hides) were used to study the effects of shade and feeding zilpaterol hydrochloride (ZH) on performance, carcass quality, heat stress, mobility, and body temperature (BT). A randomized block design with a 2 × 2 factorial treatment arrangement was used with 4 replicates per treatment. Factors included housing type (open or shaded pens) and the feeding of ZH (0 or 8.33 mg/kg DM) the last 21 d on feed with a 3-d withdrawal. Cattle were blocked by BW into a heavy or light block and randomly assigned to pen within each block. Rumen boluses to record BT were inserted before ZH feeding. Respiration rate and panting scores were recorded daily during the ZH feeding period. Mobility scores were collected at various time points from before ZH feeding through harvest. Interactions between ZH and housing type were not significant ( > 0.26) for animal performance, carcass characteristics, and respiration or panting score. No differences ( > 0.44) were observed for DMI, ADG, or G:F on a live basis due to ZH; however, cattle fed in open pens tended ( = 0.08) to have a greater ADG than cattle in shaded pens. Cattle fed ZH had 14 kg heavier carcasses with larger LM area ( < 0.01) than control cattle. Respiration rates for cattle fed ZH were greater ( = 0.05) with no differences ( = 0.88) due to housing. Time affected ( < 0.01) mobility scores, with observations on the morning of harvest at the abattoir being the worst for all groups of cattle. An interaction ( < 0.01) was observed between ZH and housing type for BT. Cattle fed ZH, in both shaded and open pens, had lower ( < 0.05) average, maximum, and area under the curve BT than control cattle fed in the same housing type. However, the observed reduction in BT due to ZH was greater for cattle fed ZH in open pens than for cattle fed ZH in shaded pens. From these results, we conclude that ZH improved HCW with little impact on heat stress or mobility, suggesting that animal welfare was not affected by feeding ZH for 21 d at the end of the feeding period.

Effects of supplemental lysine and methionine with zilpaterol hydrochloride on feedlot performance, carcass merit, and skeletal muscle fiber characteristics in finishing feedlot cattle.

Feeding zilpaterol hydrochloride (ZH) with ruminally protected AA was evaluated in a small-pen feeding trial. Crossbred steers ( = 180; initial BW = 366 kg) were blocked by weight and then randomly assigned to treatments (45 pens; 9 pens/treatment). Treatment groups consisted of no ZH and no AA (Cont-), ZH and no AA (Cont+), ZH and a ruminally protected lysine supplement (Lys), ZH and a ruminally protected methionine supplement (Met), and ZH and ruminally protected lysine and methionine (Lys+Met). Zilpaterol hydrochloride (8.3 mg/kg DM) was fed for the last 20 d of the finishing period with a 3-d withdrawal period. Lysine and Met were top dressed daily for the 134-d feeding trial to provide 12 or 4 g·hd·d, respectively, to the small intestine. Carcass characteristics, striploins, and prerigor muscle samples were collected following harvest at a commercial facility. Steaks from each steer were aged for 7, 14, 21, and 28 d, and Warner-Bratzler shear force (WBSF) was determined as an indicator of tenderness. Prerigor muscle samples were used for immunohistological analysis. Cattle treated with Met and Lys+Met had increased final BW ( < 0.3) and ADG ( < 0.05) compared to Cont- and Cont+. Supplementation of Lys, Met, and Lys+Met improved G:F ( < 0.05) compared to Cont- during the ZH feeding period (d 111 to 134) as well as the entire feeding period ( < 0.05). Zilpaterol hydrochloride increased carcass ADG ( < 0.05) when compared to non-ZH-fed steers. Methionine and Lys+Met treatments had heavier HCW ( < 0.02) than that of Cont-. Yield grade was decreased ( < 0.04) for Cont+ steers compared to steers treated with Lys, Lys+Met, and Cont-. Tenderness was reduced ( < 0.05) with ZH regardless of AA supplementation. Lysine, Met, Lys+Met, and Cont+ had less tender steaks ( < 0.05) throughout all aging groups compared to Cont-. Steaks from Lys-treated steers were less tender ( < 0.05) than those of Cont+ during the 7- and 14-d aging periods. Nuclei density was the greatest with Cont- cattle compared to all other treatments suggesting a dilution effect of the nuclei in the larger muscle fibers with ZH feeding. Supplementation of Met in conjunction with ZH feeding increased ADG and HCW although this may lead to decreased tenderness even after aging for 28 d. These findings indicated that steers fed ZH may require additional AA absorbed from the small intestine to maximize performance.

The effects of supplementation methods and length of feeding of zilpaterol hydrochloride on meat characteristics of fattening lambs

The aim of the study was to examine the effects of different methods of supplementation of zilpaterol hydrochloride (ZH) (every day, 1 d on and 1 d off or 2 d on and 2 d off) for the last 28 and 42 days of feeding period (length of feeding) on fat tail adipocyte and muscle fiber size and meat quality. Fifty six Lori-Bakhtiari feedlot lambs (initial BW=44±4.7kg) were stratified according to the BW and randomly assigned to individual pens. Lambs were fed a diet with 14% CP and 2.36Mcal/kg of ME supplemented with 0.2mg/kg of live weight d−1 ZH. Different methods of supplementation and/or feeding period of ZH had no effect (P>0.05) on ultimate pH, cooking loss, drip loss and cholesterol content of meat. Method of supplementation had a significant effect on shear force (P<0.013) with the higher value in the daily supplementation compared to intermittent days of supplementation. Lambs fed ZH daily for the last 42 days had higher shear force compared to the control group (P<0.05). There was no significant difference in fat-tail adipocyte area between the methods of ZH supplementation (P>0.05). Lambs that received ZH daily for 28 days and intermittently (1 on and 1 off for 42 d) had greater fiber area (P<0.01) compared to the control treatment fed a basal diet for 42 d without ZH. Intermittent supplementation of ZH had higher tenderness than daily supplementation (P=0.025) but, method of supplementation and length of feeding did not affect other sensory characteristics of meat. Overall, feeding ZH daily for 42 d decreased tenderness of meat, while the other meat quality characteristics were not affected in Lori-Bakhtiari fat-tail lambs.

Impact of sorting before feeding zilpaterol hydrochloride on feedlot performance and carcass characteristics of yearling steers.

Two studies evaluated sorting and feeding zilpaterol hydrochloride (ZH) on feedlot performance and carcass characteristics in randomized block-designed finishing trials. In Exp. 1 (initial BW 342 ± 10 kg, = 1,000), 5 treatments included an unsorted non-ZH fed negative control (-CON), an unsorted ZH fed positive control (+CON), and 3 treatments in which the heaviest 20% within the pen were sorted and marketed 28 d early and the remaining 80% were fed ZH. The 20% were identified at the beginning (EARLY), 100 d from slaughter (MIDDLE), or 50 d from slaughter (LATE). Because of sorting, the remaining steers in sorted treatments were fed 14 d longer than -CON and +CON. Average days on feed for control treatments were 165 and 173 d for the EARLY, MIDDLE, and LATE treatments. In Exp. 2 (initial BW 376 ± 29 kg, = 1,400), 4 treatments included -CON; +CON; an early weight sort fed ZH (1-SORT) with the heaviest 20% identified at d 1 and sorted 50 d from harvest and marketed 14 d before -CON and +CON, with the remaining 80% of the pen fed 7 d longer than -CON and +CON; and a 4-way sort 50 d from harvest fed ZH (4-SORT) with steers sorted into HEAVY, MID-HEAVY, MID-LIGHT, and LIGHT groups marketed -14, 0, +7, and +28 d from -CON and +CON, respectively. Average days on feed for control treatments were 154 and 157 d for the 1-SORT and 159 d for 4-SORT. Steers were fed Zilmax at 8.3 mg/kg DM for 20 d followed by a 3 d withdrawal. In Exp. 1, steers fed +CON had 13 kg greater (P < 0.01) HCW than steers fed -CON. Steers sorted EARLY, MIDDLE, and LATE had 28, 25, and 24 kg heavier ( P< 0.01) HCW than -CON steers, respectively. Carcass weight SD was greater (P = 0.01) for +CON than -CON but was not different (P = 0.17) between -CON and ZH sorted treatments. Percentage of overweight carcasses (454 kg) was greater (P ≤ 0.05) in sorted treatments than in -CON. In Exp. 2, HCW for +CON was 15 kg heavier (P < 0.01) than that for -CON, and HCW for 4-SORT was greater (P < 0.02) than that for +CON. Carcass weight SD was not different (P > 0.10) between +CON and -CON, whereas carcass weight SD of 4-SORT was reduced (P < 0.01) compared with that of -CON and +CON. Steers fed ZH had a greater percentage of carcasses over 454 kg than steers fed -CON (P < 0.01). Although not statistically different (P = 0.27), the percentage of carcasses over 454 kg was reduced by 28% for 4-SORT compared with +CON. Feeding ZH increases carcass weight, but sorting reduces variation, allowing further increases in carcass weight while minimizing overweight carcasses.

Effects of zilpaterol hydrochloride on growth performance, blood metabolites, and fatty acid profiles of plasma and adipose tissue in finishing steers1

The effects of zilpaterol hydrochloride (ZH) on blood metabolites and fatty acid profiles of plasma and adipose tissue were evaluated in crossbred finishing steers (n = 18, BW 639 ± 12.69 kg) that were stratified by BW and randomly assigned, within strata (block), to receive 0 (control) or 8.33 mg/kg diet DM ZH. Cattle were fed once daily ad libitum in individual feeding pens (9 pens/treatment). Zilpaterol hydrochloride was fed for 23 d and withdrawn 3 d before harvest. Blood samples and measures of BW were taken on d 0, 7, 14, and 21. Concentrations of β-hydroxybutyrate (BHB), glucose, and lactate were determined from whole blood. Nonesterified fatty acids, urea nitrogen (PUN), glucose, lactate, and long-chain fatty acid (LCFA) concentrations were analyzed from plasma. Postharvest, adipose tissue samples (approximately 20 g) from subcutaneous fat covering the lumbar vertebrae were collected after 48 h of refrigeration and analyzed for LCFA profiles. Feeding ZH decreased DMI by 8% (P = 0.03) but did not affect BW gain or efficiency (P = 0.83 and P = 0.56, respectively). Addition of ZH resulted in greater HCW, dressing percentage, and LM area ( P = 0.02, P = 0.08, and P = 0.07, respectively) but did not influence other carcass traits (P > 0.10). A ZH × d interaction was observed for PUN and whole-blood glucose concentrations (P = 0.06), in which concentrations decreased in cattle receiving ZH. Nonesterified fatty acids, BHB, plasma glucose, whole-blood, and plasma lactate concentrations were unaffected by ZH (P > 0.10). Zilpaterol hydrochloride increased plasma concentrations of elaidic (P = 0.03), vaccenic (P = 0.006), and docosapentaenoic acids ( P= 0.08), but LCFA concentrations of adipose tissue were unaffected ( P> 0.10), suggesting no preferential oxidation of specific fatty acids. In conclusion, ZH supplementation decreased PUN concentration possibly due to decreased muscle catabolism, but components of blood related to lipid oxidation were unaffected.