title: Effect of xylazine in heifers under thermoneutral or heat stress conditions.
abstract: A study was performed to assess the effect of xylazine HCl (0.1 mg/kg of body weight, IV) in heifers maintained at thermoneutrality (18 C, 42% humidity) or under heat stress (33 C, 63% humidity) conditions. Xylazine caused 50 and 70% decreases in serum insulin concentrations in the thermoneutral and heat-stressed heifers, respectively. Xylazine-induced hypoinsulinemia was associated with hyperglycemia. In the thermoneutral group, serum glucose concentrations increased from a basal concentration of 75 mg/dl to 150 mg/dl after 15 minutes. In the heat stress group, the serum glucose concentration increased from 65 mg/dl to 105 mg/dl. Hyperglycemia peaked at 2 hours and remained high for 6 hours after xylazine administration. Heat-stressed heifers took a longer time (107 minutes) to stand than did heifers under thermoneutral conditions (41 minutes). The time to regain sensation to pain was significantly prolonged in heat-stressed heifers. Xylazine had no effect on body temperature and respiration rate in heifers under the thermoneutral condition, whereas it markedly induced hyperthermia and suppressed respiration rate in the heat-stressed heifers. Furthermore, the pulse rate was slightly decreased in thermoneutral heifers and was markedly decreased in the heat-stressed heifers.
authors.affiliation: Department of Dairy Science, University of Missouri-Columbia 65211.
authors.forename: A H
authors.initials: AH
authors.lastname: Fayed
authors.forename: E B
authors.initials: EB
authors.lastname: Abdalla
authors.forename: R R
authors.initials: RR
authors.lastname: Anderson
authors.forename: K
authors.initials: K
authors.lastname: Spencer
authors.forename: H D
authors.initials: HD
authors.lastname: Johnson
mesh_terms: D000818:Animals; D001786:Blood Glucose / Q000032:analysis; D001831:Body Temperature / Q000187:drug effects; D002417:Cattle; D002418:Cattle Diseases / Q000503:physiopathology*; D005260:Female; D006358:Hot Temperature; D007328:Insulin / Q000097:blood; D011674:Pulse / Q000187:drug effects; D012119:Respiration / Q000187:drug effects; D013312:Stress, Physiological / Q000503:physiopathology / Q000662:veterinary*; D013843:Thiazines / Q000494:pharmacology*; D014991:Xylazine / Q000494:pharmacology*
chemical_list: D001786:Blood Glucose; D007328:Insulin; D013843:Thiazines; D014991:Xylazine