title: Effects of zilpaterol hydrochloride with or without an estrogen-trenbolone acetate terminal implant on carcass traits, retail cutout, tenderness, and muscle fiber diameter in finishing steers.
abstract: Our objective was to determine the effects of feeding zilpaterol hydrochloride (ZH), a beta-agonist, for the final 30 d of the feeding period, with or without a terminal estrogen + trenbolone acetate (TBA) implant (Revalor-S; 24 mg of estradiol-17beta and 120 mg of TBA; REV) on meat tenderness and carcass cutout yields. Crossbred steers (n = 2,279) were divided into 6 BW blocks and 24 pens. Within each block, pens were assigned randomly to 1 of 4 treatments: 1) no terminal implant (control); 2) a terminal REV given 91 d before slaughter; 3) no terminal implant plus ZH; and 4) a terminal REV implant plus ZH (REV+ZH). All cattle received Component TE-IS (16 mg of estradiol and 80 mg of TBA) on d - 61 of the feeding period [corrected]. Zilpaterol hydrochloride was added to the diets at a concentration of 8.38 mg/kg (DM basis) during the final 30 d of the feeding period, followed by a 3-d period before slaughter in which ZH was withdrawn from the diet. Carcasses (n = 30/treatment) were selected from the 2,279 cattle and fabricated into subprimal cuts as per Institutional Meat Purchase Specifications. Strip loins were collected, cut into 2.54-cm steaks, and aged 7, 14, and 21 d, after which Warner-Bratzler shear force (WBSF), collagen content, desmin degradation, and muscle fiber diameter measurements were determined. Feeding ZH increased (P < 0.05) yield of the #112A ribeye roll, #116B chuck mock tender, #167A peeled knuckle, #169 top inside round, #171B outside round, #171C eye of round, #180 strip loin, #184 top sirloin butt, and #189A full tenderloin for ZH treatment. Longissimus muscle WBSF at 7, 14, and 21 d postmortem was increased (P < 0.001) with ZH supplementation. Desmin degradation at 7, 14, and 21 d postmortem was not affected with REV or ZH supplementation compared with controls. Zilpaterol hydrochloride had an additive effect with REV on increasing LM fiber diameter (P < 0.001). When fed to cattle that received a terminal implant of REV, ZH potentially increased LM WBSF as a result of induced muscle hypertrophy. During the 21-d aging period, WBSF decreased with aging, suggesting that carcasses from cattle supplemented with ZH might require longer aging time to ensure that acceptable levels of tenderness are reached.
authors.affiliation: Department of Animal and Food Sciences, Texas Tech University, Lubbock 79409, USA.
authors.forename: J D
authors.initials: JD
authors.lastname: Kellermeier
authors.forename: A W
authors.initials: AW
authors.lastname: Tittor
authors.forename: J C
authors.initials: JC
authors.lastname: Brooks
authors.forename: M L
authors.initials: ML
authors.lastname: Galyean
authors.forename: D A
authors.initials: DA
authors.lastname: Yates
authors.forename: J P
authors.initials: JP
authors.lastname: Hutcheson
authors.forename: W T
authors.initials: WT
authors.lastname: Nichols
authors.forename: M N
authors.initials: MN
authors.lastname: Streeter
authors.forename: B J
authors.initials: BJ
authors.lastname: Johnson
authors.forename: M F
authors.initials: MF
authors.lastname: Miller
mesh_terms: D045930:Anabolic Agents / Q000008:administration & dosage / Q000494:pharmacology*; D000818:Animals; D002417:Cattle / Q000502:physiology*; D003094:Collagen / Q000032:analysis; D004343:Drug Implants; D005503:Food Additives / Q000008:administration & dosage / Q000494:pharmacology*; D008297:Male; D008460:Meat / Q000032:analysis / Q000592:standards*; D018482:Muscle, Skeletal / Q000033:anatomy & histology / Q000187:drug effects; D014204:Trenbolone Acetate / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000494:pharmacology; D014297:Trimethylsilyl Compounds / Q000008:administration & dosage / Q000494:pharmacology*
chemical_list: D045930:Anabolic Agents; D004343:Drug Implants; D005503:Food Additives; D014297:Trimethylsilyl Compounds; C475840:Zilpaterol; D003094:Collagen; D014204:Trenbolone Acetate