Semester of Graduation

December 2019

Degree

Master of Science (MS)

Department

School of Animal Sciences

Document Type

Thesis

Abstract

Excitement is a problem when conducting endocrine tests on fractious horses. Epinephrine (EPI), for example, was shown to obliterate the insulin-induced decrease in blood glucose concentrations. Sedation may be a solution; however, perturbation of results may preclude useful information. The objectives of the four experiments presented herein were 1) to determine the effects of EPI on insulin response to glucose infusion (IR2G), 2) to assess the effects of the α-adrenergic sedative, detomidine (DET), alone or in combination with the opioid agonist, butorphanol (BUT), on IR2G and glucose response to insulin (GR2I), and 3) to assess the effects of BUT alone on IR2G. In Experiment 1, mares were administered saline or EPI (5 ug/kg, intravenously) immediately before infusion of glucose (100 mg/kg BW). Glucose caused peak rise (P < .05) in plasma insulin in controls at 5 minutes that persisted through 30 minutes; insulin was suppressed (P < .05) by EPI from 5 to 15 minutes, rising gradually through 30 minutes. Experiments 2 (IR2G) and 3 (GR2I) were carried out as separate triplicated 3 x 3 Latin square designs with the following treatments: saline (SAL), DET, and the combination of DET/BUT, all administered intravenously at .01 mg/kg BW. There was a 6-day washout period between phases. Blood samples from indwelling catheters were collected at -10 and 0 minutes before treatment, and continued every 5 minutes for 40 minutes. Infusion of glucose occurred 10 minutes after sedation. Glucose caused an immediate rise (P < .05) in plasma insulin that persisted through 30 minutes in SAL mares; DET and DET/BUT severely suppressed (P < .0001) the IR2G. To assess the GR2I in Experiment 3, blood glucose was measured after treatment with recombinant human insulin (50 mIU/kg BW, intravenously). Sedation did not affect resting blood glucose and had inconsistent effects on the GR2I. The administration of BUT alone in Experiment 4 had no effect on IR2G. In conclusion, adrenergic agonists severely suppress the IR2G and cannot be used for sedation for this test. The use of DET did not alter the GR2I, and therefore may be useful for conducting this test in fractious horses.

Date

8-8-2019

Committee Chair

Thompson, Donald L., Jr

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