Effect of zilpaterol hydrochloride duration of feeding on performance and carcass characteristics of feedlot cattle1

Abstract

Four trials, each with a randomized complete block design, were conducted with 8,647 beef steers (initial BW = 346 +/- 29.6 kg) in 3 different locations in the United States to evaluate the effects of zilpaterol hydrochloride (ZH) on performance and carcass characteristics of feedlot cattle. Treatments consisted of feeding ZH (8.33 mg/kg of dietary DM) for 0, 20, 30, or 40 d, at the end of the feeding period, followed by a 3-d withdrawal period before slaughter. Cattle were weighed on d 0 and 50 before slaughter (in 3 of the 4 studies), and on the day of slaughter. Data from the 4 trials were pooled for statistical analyses. No differences (P > or = 0.78) were detected among treatments for ADG and G:F from the start of the study until the final 50 d on feed. Final BW was greater for the average of the 3 ZH-treated groups (P < 0.01) than for the 0-d group. Average daily gain was greater for ZH-treated vs. control cattle during the final 50 d on feed (P < 0.01) and for the entire feeding period (P < 0.01). No differences in DMI were noted for any periods of the experiment (P > or = 0.42) for ZH-treated cattle vs. controls. No differences were noted for DMI among the ZH-treated groups for the final 50 d on feed (P = 0.81) or for the overall feeding period (P = 0.31). Feeding ZH for any length of time increased G:F (P < 0.01) for the final 50 d and overall compared with 0-d cattle. In addition, a linear increase with more days of ZH feeding was observed for G:F during the period that ZH was fed (P = 0.01), as well as for the overall feeding period (P = 0.01). The ZH-treated cattle had heavier HCW (P < 0.01), greater dressing percent (P < 0.01), reduced marbling scores (P < 0.01), less 12th-rib fat (P < 0.01), larger LM area (P < 0.01), less KPH (P = 0.01), and a lower USDA yield grade (P < 0.01) than the 0-d cattle, regardless of the duration of ZH feeding. Dressing percent increased linearly (P < 0.01) with increased duration of ZH feeding, whereas 12th-rib fat (P = 0.07), marbling scores (P < 0.01), and USDA calculated yield grade (P = 0.01) decreased linearly with increased duration of ZH feeding. Feeding ZH increased ADG and G:F and decreased overall carcass fatness. In addition, effects of ZH on measures of carcass fatness were enhanced by feeding the product for a greater length of time.

Non-inferiority trial of two commercial zilpaterol HCl brands in <em>Bos indicus</em> cattle under humid tropical conditions

“…34,40 Elam et al treated Bos taurus bulls with 8.33 mg ZH/kg feed as dry matter for 30 days and obtained final weight increments of 9.3 kg compared with untreated bulls. 42 These values are similar to those obtained in this trial for Bos indicus (i.e., final weight increments of 7.75 kg at a dose of 6 mg of generic ZH/kg feed). The mean final weight reported by Avendaño et al using a generic ZH, was higher than the one achieved here 21 ; however, the weight gain reported by these authors was similar to the corresponding value obtained during this trial (e.g., 77.80 vs. 53.16, respectively).…”

“…Most trials using the reference ZH brand were conducted in temperate/cold areas, which have predominant Bos taurus bulls 33,[42][43][44] . After a thorough literature review, only two trials could be compared with the one described here.…”

Comparative effects of zilpaterol hydrochloride and ractopamine hydrochloride on live performance and carcass characteristics of calf-fed Holstein steers12

“…Calf-fed Holstein steers fed ZH had an increased (P < 0.01) percentage of USDA Select grading carcass (31.0) and a decreased (P < 0.01) percentage of USDA Choice grading carcasses (65.0) compared with steers fed RH (25.8,70.2) or the control diet (24.8, 72.0), respectively. The results from the current study with respect to QG are generally consistent with those of Beckett et al (2009) and Elam et al (2009), who collectively reported feeding ZH increased the percentage of USDA Select grading carcasses (11.7% to 12.3%) and decreased the percentage of USDA Choice grading carcasses (5.8% to 12.0%) over cattle fed no β-agonist. No differences (P ≥ 0.49) were observed between treatments for the percentage of USDA Standard or Prime grading carcasses.…”

Perspectives on the application of zilpaterol hydrochloride in the United States beef industry

“…Skeletal, lean, overall maturity, color, and dark cutter scores were not affected by feeding ZH. Steer studies have demonstrated no difference in lean maturity when fed ZH 0, 20, 30, or 40 d or when the cattle had differ ent days on feed (Vasconcelos et al, 2008;Elam et al, 2009). Hilton et al (2009) found LM steaks from cattle fed ZH 30 d, vacuum-aged 14 d postmortem, and pack aged with polyvinyl chloride (PVC) film for retail dis play maintained a brighter cherry red color throughout the 5-d retail display than did the controls.…”

“…Interestingly, even though BW is increased an aver age of 9 kg in beef steers fed ZH compared with control steers, HCW was increased approximately 15 kg (Vas concelos et al, 2008;Elam et al, 2009). The increase in HCW relative to BW resulted in changes in dressing percent.…”