title: The effects of technology use in feedlot production systems on feedlot performance and carcass characteristics.
abstract: The objectives of this study were to examine the effects of feedlot production systems with and without the use of a β-adrenergic agonist compared to an all-natural production program on feedlot performance and carcass characteristics. Crossbred beef steers ( = 336; initial BW = 379 ± 8 kg) were randomized to 1 of 3 treatments in a randomized complete block design (RCBD; 14 steers/pen; 8 pens/treatment). Treatments consisted of an all-natural treatment (NAT), a conventional treatment (CONV), and a conventional treatment with a β-agonist (CONV-Z). All treatments were fed the same basal diet with NAT cattle receiving no growth promoting technologies. The CONV and CONV-Z cattle were implanted with 40 mg of estradiol and 200 mg of trenbolone acetate (TBA) on d 0 and were fed 33 and 9 mg/kg of monensin and tylosin daily, respectively. The CONV-Z cattle were fed zilpaterol hydrochloride (ZH) at 6.76 mg/kg (90% DM basis) for the last 20 days on feed (DOF) There was no effect of treatment on DMI ( = 0.83); however, CONV-Z steers gained 3.8% faster (1.64 vs. 1.58 kg/d; < 0.01) and were 5.3% more efficient (0.160 vs. 0.152; < 0.01) than CONV steers, and CONV steers gained 32.8% faster (1.58 vs. 1.19 kg/d; < 0.01) and were 26.7% more efficient (0.152 vs. 0.120; < 0.01) than NAT steers. There was a 35.7% improvement in estimated carcass gain (1.29 vs. 0.95 kg/d; < 0.01) and a 32.6% improvement in carcass efficiency (0.126 vs. 0.095; < 0.01) for CONV-Z steers compared to NAT steers. Hot carcass weight was increased by 8 kg for CONV-Z steers compared to CONV steers (394 vs. 386 kg; = 0.05) and 46 kg compared to NAT steers (394 vs. 348 kg; < 0.01). Longissimus muscle area was increased by 3.6 cm for CONV-Z steers compared to CONV steers (92.29 vs. 88.67 cm; = 0.02) and 12.1 cm for CONV-Z steers compared to NAT steers (92.29 vs. 80.16 cm; < 0.01), resulting in a 9.6% unit increase in USDA yield grade (YG) 1 (15.14 vs. 5.52%; < 0.05) and a 21.6% unit reduction in USDA YG 3 for CONV-Z steers compared to CONV steers (30.70 vs. 52.32%; < 0.05). The CONV-Z steers had a lower marbling score compared to the other treatments (432; 0.01), resulting in an 11.7% unit increase (20.70 vs. 9.03%; < 0.05) in USDA Select carcasses compared to CONV steers. The results of this experiment show that CONV-Z and CONV production results in a significant improvement in feedlot performance and USDA YG compared to NAT.
authors.forename: C L
authors.initials: CL
authors.lastname: Maxwell
authors.forename: B C
authors.initials: BC
authors.lastname: Bernhard
authors.forename: C F
authors.initials: CF
authors.lastname: O'Neill
authors.forename: B K
authors.initials: BK
authors.lastname: Wilson
authors.forename: C G
authors.initials: CG
authors.lastname: Hixon
authors.forename: C L
authors.initials: CL
authors.lastname: Haviland
authors.forename: A N
authors.initials: AN
authors.lastname: Grimes
authors.forename: M S
authors.initials: MS
authors.lastname: Calvo-Lorenzo
authors.forename: D L
authors.initials: DL
authors.lastname: VanOverbeke
authors.forename: G G
authors.initials: GG
authors.lastname: Mafi
authors.forename: C J
authors.initials: CJ
authors.lastname: Richards
authors.forename: D L
authors.initials: DL
authors.lastname: Step
authors.forename: B P
authors.initials: BP
authors.lastname: Holland
authors.forename: C R
authors.initials: CR
authors.lastname: Krehbiel
mesh_terms: D018663:Adrenergic Agents / Q000008:administration & dosage / Q000494:pharmacology; D000318:Adrenergic beta-Agonists / Q000494:pharmacology*; D000818:Animals; D000900:Anti-Bacterial Agents / Q000008:administration & dosage / Q000494:pharmacology; D001823:Body Composition / Q000187:drug effects* / Q000502:physiology; D002417:Cattle / Q000254:growth & development* / Q000502:physiology; D004032:Diet / Q000662:veterinary; D004958:Estradiol / Q000008:administration & dosage / Q000494:pharmacology; D006728:Hormones / Q000008:administration & dosage / Q000494:pharmacology*; D008297:Male; D008985:Monensin / Q000008:administration & dosage / Q000494:pharmacology; D061209:Proton Ionophores / Q000008:administration & dosage / Q000494:pharmacology; D014204:Trenbolone Acetate / Q000008:administration & dosage / Q000494:pharmacology; D014297:Trimethylsilyl Compounds / Q000008:administration & dosage / Q000494:pharmacology; D015645:Tylosin / Q000008:administration & dosage / Q000494:pharmacology; D015430:Weight Gain / Q000187:drug effects* / Q000502:physiology
chemical_list: D018663:Adrenergic Agents; D000318:Adrenergic beta-Agonists; D000900:Anti-Bacterial Agents; D006728:Hormones; D061209:Proton Ionophores; D014297:Trimethylsilyl Compounds; C475840:Zilpaterol; D004958:Estradiol; D008985:Monensin; D014204:Trenbolone Acetate; D015645:Tylosin