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Cactus, TX, United States

Rathmann R.J.,Texas Tech University | Bernhard B.C.,Texas Tech University | Swingle R.S.,Cactus Research Ltd | Lawrence T.E.,West Texas A&M University | And 7 more authors.
Journal of Animal Science | Year: 2012

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. © 2012 American Society of Animal Science. All rights reserved.


Parr S.L.,Texas Tech University | Chung K.Y.,Texas Tech University | Hutcheson J.P.,Schering | Nichols W.T.,Schering | And 5 more authors.
Journal of Animal Science | Year: 2011

Four experiments evaluated the effect of implant dose and release pattern on performance and carcass traits of crossbred beef steers. In Exp. 1, steers (4 to 7 pens/treatment; initial BW = 315 kg) were fed an average of 174 d. Treatments were 1) no implant (NI); 2) Revalor-S [120 mg of trenbolone acetate (TBA) and 24 mg of estradiol 17β (E 2); REV-S]; 3) Revalor-IS followed by REV-S (cumulatively 200 mg of TBA and 40 mg of E 2; reimplanted at 68 to 74 d; REVIS/ S); and 4) Revalor-XS (200 mg of TBA and 40 mg of E 2; REV-X). Carcass-adjusted final BW was greater (P < 0.05) for REV-X and REV-IS/S than for REV-S (610, 609, and 598 kg, respectively). Daily DMI did not differ (P > 0.10) among the 3 implants, but carcassadjusted G:F was greater (P < 0.05) for REV-X and REV-IS/S than for REV-S (0.197 and 0.195 vs. 0.188). Both HCW and LM area were greater (P < 0.05) for REV-X and REV-IS/S than for REV-S. Marbling scores were greatest (P < 0.05) for REV-S and least (P < 0.05) for REV-IS/S; REV-X was intermediate to NI and REV-IS/S. In Exp. 2, steers (10 pens/treatment; initial BW = 391 kg) were fed 131 d, with treatments of REV-S, REV-IS/S (reimplanted at 44 to 47 d), and REV-X. Carcass-adjusted final BW (598 kg), ADG (1.6 kg), DMI (9.4 kg), G:F (0.17), and HCW did not differ (P > 0.10) among treatments. The percentage of Choice was less (P < 0.05) and percentage of Select greater (P < 0.05) for REV-IS/S than for REV-S and REV-X. In Exp. 3, steers (10 pens/treatment; initial BW = 277 kg) were fed 197 d and received either REVIS/ S (reimplanted at 90 to 103 d) or REV-X. Carcassadjusted final BW (625 vs. 633 kg) and ADG (1.81 vs. 1.76 kg) were greater (P < 0.05) for REV-X-implanted steers. Daily DMI did not differ, but G:F tended (P < 0.10) to be increased and HCW was greater (P < 0.05) for REV-X than for REV-IS/S. In Exp. 4, steers (8 pens/treatment; initial BW = 238 kg) were fed 243 d and received either REV-IS/S (reimplanted at 68 to 71 d) or REV-X. Carcass-adjusted final BW (612 kg), ADG (1.54 kg), DMI (7.55), and G:F (0.21) did not differ (P > 0.10) for REV-IS/S and REV-X-implanted steers. Carcass traits did not differ among implants, but the percentage of Choice carcasses was greater (P < 0.05) and percentage of Select was less (P < 0.05) for REV-X than for REV-IS/S. These data indicate that when TBA/E 2 dose is equal, the altered release rate of REV-X can improve performance and quality grade, but these effects depend on duration of the feeding period and timing of initial and terminal implants. © 2011 American Society of Animal Science. All rights reserved.


McEvers T.J.,West Texas A&M University | Walter L.J.,West Texas A&M University | Defoor P.J.,Cactus Research Ltd | Swingle R.S.,Cactus Research Ltd | And 2 more authors.
Journal of Animal Science | Year: 2014

The focus of this investigation was to identify interactions that may exist among alleles of the leptin gene and supplementation of zilpaterol hydrochloride (ZH). Steers (n = 4,246; initial BW = 389.8 ± 8.8 kg) were genotyped and sorted into 1 of 3 leptin genotype (LG) groups (homozygous normal [CC], heterozygous [CT], or homozygous mutant [TT]) from a candidate pool of 7,506 steers. Steers were allocated into 48 pens of which one-half were fed the β-adrenergic agonist ZH and the balance, a control diet. During the pretreatment period (d 1 to 102), cattle of the TT genotype exhibited increased (P = 0.02) DMI compared to other genotypes and lower G:F than the CC genotype (P = 0.03). Cattle of the CT genotype had lower (P = 0.02) ADG compared to other genotypes for the treatment period. Cattle fed ZH had improved (P < 0.01) ADG and G:F compared to cattle on the control diet for both the treatment and entire study periods (d 1 to 125). For the entire study period, cattle of the TT genotype had greater (P = 0.03) DMI than the CT allele, with CT cattle having the lowest (P < 0.01) ADG and CC cattle having greatest (P < 0.01) G:F of all alleles. Cattle of the TT genotype had greater (P = 0.03) final shrunk weight than the CT allele. Cattle of the TT genotype had lower (P = 0.04) dressed yield compared to CT cattle and greater (P = 0.01) marbling score compared to CC cattle, with a concurrent increase (P < 0.01) in calculated empty body fat (EBF) over all alleles. Cattle fed ZH had greater (P < 0.01) final shrunk weight, HCW, dressed yield, and LM area coupled with reduced (P < 0.01) marbling score, s.c. fat depth, EBF, and calculated USDA yield grade compared to control steers. Carcasses of the TT allele had a greater (P = 0.01) proportion of Choice carcasses than CT or CC alleles and lesser (P = 0.03) proportion of Select carcasses than CC alleles. Additionally, ZH supplemented cattle had fewer (P < 0.01) carcasses grading Premium Choice or better, Choice, and yield grade 3, 4, and 5 with subsequently more (P < 0.01) carcasses grading Select, Standard, and yield grade 1. Differences in live and carcass performance exist among leptin alleles, which may allow for sorting and improved timeliness of fed beef marketing. © 2014 American Society of Animal Science. All rights reserved.

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