Effects of duration of zilpaterol hydrochloride feeding and days on the finishing diet on feedlot cattle performance and carcass traits. 2008

J T Vasconcelos, and R J Rathmann, and R R Reuter, and J Leibovich, and J P McMeniman, and K E Hales, and T L Covey, and M F Miller, and W T Nichols, and M L Galyean
Department of Animal and Food Sciences, Texas Tech University, Lubbock 79409, USA. jvasconcelos2@unl.edu

British and British x Continental steers (n = 560; initial BW = 339.4 +/- 1.76 kg) were used in a serial slaughter study with a completely random design to evaluate effects of zilpaterol hydrochloride (ZH; 8.33 mg/kg of dietary DM basis) on performance and carcass characteristics. Treatments were arranged in a 4 x 4 factorial (112 pens; 7 pens/treatment; 5 steers/pen) and included duration of ZH feeding (0, 20, 30, or 40 d before slaughter plus a 3-d ZH withdrawal period) and days on feed (DOF) before slaughter (136, 157, 177, and 198 d). No duration of ZH feeding x slaughter group interactions were detected for the performance measurements (P > 0.10). Final BW did not differ (P = 0.15) between the 0-d group and the average of the 3 ZH groups, but ADG was greater for the average of the 3 ZH groups during the period in which ZH diets were fed (P < 0.01) and for the overall feeding period (P = 0.05). As duration of ZH feeding increased, DMI decreased (P = 0.01) and G:F increased linearly (P < 0.01). With the exception of KPH (P = 0.022), no duration of ZH feeding x slaughter group interactions (P > 0.10) were detected for carcass characteristics. Regardless of the duration of ZH feeding, cattle fed ZH had greater HCW (P < 0.01), greater dressing percent (P < 0.01), less 12th-rib fat (P < 0.01), larger LM area (P < 0.01), less KPH (P = 0.03), and lower yield grade (P < 0.01) than the 0-d cattle. The 0-d group had greater marbling scores (P < 0.01) than cattle fed ZH diets, with a tendency for a linear decrease in marbling score (P = 0.10) as duration of ZH feeding was extended. A greater percentage of carcasses in the 0-d group graded USDA Choice or greater (P < 0.01) than in the 3 ZH groups, whereas the percentage of Select carcasses was greater (P = 0.01) for the 3 ZH groups. From d 0 to end (P = 0.04) and during the last 43 d on feed (P < 0.01), ADG responded quadratically to DOF before slaughter. No differences were detected among slaughter groups for DMI for the entire trial period; however, a quadratic response (P = 0.02) was observed for the final 43 d before slaughter. A quadratic response was also detected for the final 43 d before slaughter (P < 0.01) and from d 0 to end (P = 0.02) for G:F. Final BW, HCW, dressing percent, and 12th-rib fat increased linearly (P < 0.01) as DOF before slaughter increased. Our results indicate that no substantial effects on performance and carcass measurements were observed when ZH was fed for 30 or 40 d as opposed to 20 d, and that effects of ZH generally did not interact with DOF before slaughter.

UI MeSH Term Description Entries
D002417 Cattle Domesticated bovine animals of the genus Bos, usually kept on a farm or ranch and used for the production of meat or dairy products or for heavy labor. Beef Cow,Bos grunniens,Bos indicus,Bos indicus Cattle,Bos taurus,Cow,Cow, Domestic,Dairy Cow,Holstein Cow,Indicine Cattle,Taurine Cattle,Taurus Cattle,Yak,Zebu,Beef Cows,Bos indicus Cattles,Cattle, Bos indicus,Cattle, Indicine,Cattle, Taurine,Cattle, Taurus,Cattles, Bos indicus,Cattles, Indicine,Cattles, Taurine,Cattles, Taurus,Cow, Beef,Cow, Dairy,Cow, Holstein,Cows,Dairy Cows,Domestic Cow,Domestic Cows,Indicine Cattles,Taurine Cattles,Taurus Cattles,Yaks,Zebus
D004032 Diet Regular course of eating and drinking adopted by a person or animal. Diets
D004334 Drug Administration Schedule Time schedule for administration of a drug in order to achieve optimum effectiveness and convenience. Administration Schedule, Drug,Administration Schedules, Drug,Drug Administration Schedules,Schedule, Drug Administration,Schedules, Drug Administration
D000818 Animals Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA. Animal,Metazoa,Animalia
D000821 Animal Feed Foodstuff used especially for domestic and laboratory animals, or livestock. Fodder,Animal Feeds,Feed, Animal,Feeds, Animal,Fodders
D000824 Animal Nutritional Physiological Phenomena Nutritional physiology of animals. Animal Nutrition Physiology,Animal Nutritional Physiology Phenomena,Animal Nutritional Physiological Phenomenon,Animal Nutritional Physiology,Animal Nutritional Physiology Phenomenon,Veterinary Nutritional Physiology,Nutrition Physiologies, Animal,Nutrition Physiology, Animal,Nutritional Physiology, Animal,Nutritional Physiology, Veterinary,Physiology, Animal Nutrition,Physiology, Animal Nutritional,Physiology, Veterinary Nutritional
D014297 Trimethylsilyl Compounds Organic silicon derivatives used to characterize hydroxysteroids, nucleosides, and related compounds. Trimethylsilyl esters of amino acids are used in peptide synthesis. Compounds, Trimethylsilyl
D015430 Weight Gain Increase in BODY WEIGHT over existing weight. Gain, Weight,Gains, Weight,Weight Gains
D018663 Adrenergic Agents Drugs that act on adrenergic receptors or affect the life cycle of adrenergic transmitters. Included here are adrenergic agonists and antagonists and agents that affect the synthesis, storage, uptake, metabolism, or release of adrenergic transmitters. Adrenergic,Adrenergic Agent,Adrenergic Drug,Adrenergic Neuron Agents,Adrenergic Release Inhibitors,Adrenergic Synthesis Inhibitors,Sympathetic Transmitter Releasers,Adrenergic Drugs,Adrenergic Effect,Adrenergic Effects,Adrenergic Neurohumor Depleters,Adrenergic Neuron Drugs,Adrenergics,Agent, Adrenergic,Agents, Adrenergic,Agents, Adrenergic Neuron,Depleters, Adrenergic Neurohumor,Drug, Adrenergic,Drugs, Adrenergic,Drugs, Adrenergic Neuron,Effect, Adrenergic,Effects, Adrenergic,Inhibitors, Adrenergic Release,Inhibitors, Adrenergic Synthesis,Neurohumor Depleters, Adrenergic,Neuron Agents, Adrenergic,Neuron Drugs, Adrenergic,Release Inhibitors, Adrenergic,Releasers, Sympathetic Transmitter,Synthesis Inhibitors, Adrenergic,Transmitter Releasers, Sympathetic

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