Effects of zilpaterol hydrochloride and days on the finishing diet on feedlot performance, carcass characteristics, and tenderness in beef heifers1

Abstract

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.

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

“…The magnitude of improvement in final body weight (22 %), lies near the maximum value reported in the literature (25 %), using the reference brand ZH. 4,[31][32][33][34][35][36][37][38][39] For example, weight gain coincides greatly with other studies conducted on Bos taurus bulls. 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.…”

Effect of growth-promoting technologies on Longissimus lumborum muscle fiber morphometrics, collagen solubility, and cooked meat tenderness12

“…When ZH was added to the GP program and compared to the CON carcasses, HCW, yield grade, and LM area were increased by 5%, 33%, and 18%, respectively. The increase in HCW is comparable to other studies Robles-Estrada et al, 2009;Rathmann et al, 2012); however, the increase in LM area and yield grade are much greater than these studies, which may be due to the combination of GP utilized in the COMBO treatment. Montgomery et al (2009) found that heifers supplemented ZH without being administered anabolic implants had only a 9% increase in LM area and yield grade when compared to heifers not subjected to GP technologies.…”

“…In agreement with the current study, Garber et al (1990) found that implanting heifers with Synovex-H did not affect G:F; however, ADG was improved by the implant. The addition of ZH to feedlot diets provides equally impressive results by increasing ADG and G:F by up to 18% and 25% , respectively Rathmann et al, 2012). In the current study, combining the implant regimen with ZH did not improve feedlot performance of the heifers when compared to controls; however, the magnitude of increase in ADG and G:F were similar to improvements reported in literature (22% and 18%, respectively).…”

“…Montgomery et al (2009) found that heifers supplemented ZH without being administered anabolic implants had only a 9% increase in LM area and yield grade when compared to heifers not subjected to GP technologies. Both Robles-Estrada et al (2009) and Rathmann et al (2012) employed an anabolic implant in their control treatment and found that ZH can increase LM area and yield grade by only 6% and 9%, respectively. This is similar to the current study, but the difference between the COMBO and IMP treatments were not significant.…”

“…Leheska et al (2009) also found that heifers supplemented the same dosage of ZH produced steaks that were 24% greater in WBSF values after 28 DOA. Other studies also indicate that aging up to 35 d postmortem will not alleviate the negative impacts of ZH on objective tenderness Garmyn et al, 2011;Rathmann et al, 2012). In the current study, steaks from the COMBO treatment had greater WBSF values through 14 DOA, where they were 40% and 24% greater than CON and IMP steaks, respectively.…”