title: The metabolic, stress axis, and hematology response of zilpaterol hydrochloride supplemented beef heifers when exposed to a dual corticotropin-releasing hormone and vasopressin challenge.
abstract: The objective of this study was to determine the metabolic, stress, and hematology response of beef heifers supplemented with zilpaterol hydrochloride (ZH) when exposed to an endocrine stress challenge. Heifers ( = 20; 556 ± 7 kg BW) were randomized into 2 treatment groups: 1) control (CON), no ZH supplementation, and 2) zilpaterol (ZIL), supplemented with ZH at 8.33 mg/kg (DM basis). The ZIL group was supplemented ZH for 20 d, with a 3-d withdrawal period. On d 24, heifers received an intravenous bolus of corticotropin-releasing hormone (CRH; 0.3 µg/kg BW) and arginine vasopressin (VP; 1.0 µg/kg BW) to activate the stress axis. Blood samples were collected at 30-min intervals for serum and 60-min intervals for plasma and whole blood, from -2 to 8 h relative to the challenge at 0 h (1000 h). Samples were analyzed for glucose, insulin, NEFA, blood urea nitrogen (BUN), cortisol, epinephrine, norepinephrine, and complete blood cell counts. Following the challenge, cattle were harvested over a 3-d period. Liver, LM, and biceps femoris (BF) samples were collected and analyzed for glucose, lactate, and glycolytic potential (GP). There was a treatment ( ≤ 0.001) effect for vaginal temperature (VT), with ZIL having a 0.1°C decrease in VT when compared with CON. A treatment × time effect ( = 0.002) was observed for NEFA. A treatment effect was observed for BUN; ZIL had decreased BUN concentrations compared with CON ( < 0.001) prior to the challenge; however, no treatment × time effect was observed. There was also a treatment effect for cortisol ( ≤ 0.01) and epinephrine ( = 0.003); ZIL had decreased cortisol and epinephrine during the CRH/VP challenge when compared with CON. There was a time effect for total white blood cells, lymphocytes, and monocytes; each variable increased ( ≤ 0.01) 2 h postchallenge. Additionally, neutrophil counts decreased ( ≤ 0.01) in response to CRH/VP challenge in both treatment groups. Glucose concentrations within the LM were greater ( = 0.03) in CON when compared with ZIL. Lactate concentrations and GP within the BF were greater in CON ( = 0.05) when compared with ZIL. These data suggest there are some variations observed between treatments in terms of response to the CRH/VP challenge; however, in the environmental conditions of this trial, none of the variations observed suggest that the supplementation of ZH detrimentally alters the ability of cattle to effectively respond to stressful stimuli.
authors.forename: J O
authors.initials: JO
authors.lastname: Buntyn
authors.forename: N C
authors.initials: NC
authors.lastname: Burdick Sanchez
authors.forename: T B
authors.initials: TB
authors.lastname: Schmidt
authors.forename: G E
authors.initials: GE
authors.lastname: Erickson
authors.forename: S E
authors.initials: SE
authors.lastname: Sieren
authors.forename: S J
authors.initials: SJ
authors.lastname: Jones
authors.forename: J A
authors.initials: JA
authors.lastname: Carroll
mesh_terms: D000318:Adrenergic beta-Agonists / Q000494:pharmacology*; D000818:Animals; D001772:Blood Cell Count / Q000662:veterinary; D001786:Blood Glucose / Q000032:analysis; D001806:Blood Urea Nitrogen; D002417:Cattle / Q000502:physiology*; D003346:Corticotropin-Releasing Hormone / Q000008:administration & dosage; D004032:Diet / Q000662:veterinary; D019587:Dietary Supplements; D005260:Female; D000070633:Hamstring Muscles / Q000187:drug effects / Q000378:metabolism; D006405:Hematology; D006728:Hormones / Q000008:administration & dosage*; D007328:Insulin / Q000097:blood; D013312:Stress, Physiological / Q000187:drug effects; D014297:Trimethylsilyl Compounds / Q000494:pharmacology*; D014667:Vasopressins / Q000008:administration & dosage
chemical_list: D000318:Adrenergic beta-Agonists; D001786:Blood Glucose; D006728:Hormones; D007328:Insulin; D014297:Trimethylsilyl Compounds; C475840:Zilpaterol; D014667:Vasopressins; D003346:Corticotropin-Releasing Hormone