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Date Available

12-9-2015

Year of Publication

2015

Document Type

Master's Thesis

Degree Name

Master of Science (MS)

College

Agriculture, Food and Environment

Department/School/Program

Animal and Food Sciences

Faculty

Dr. Eric S. Vanzant

Faculty

Dr. David L. Harmon

Abstract

Acute phase responses (APR) and circadian rhythm of body temperature (CRT) changes to a minor, chronic stressor (endophyte) and major, acute stressor, lipopolysaccharide (LPS) were evaluated in two experiments (E1:22 heifers; E2:24 heifers). Vaginal (E1 and E2) and rectal (E2) temperature probes recorded body temperature. Temperature was analyzed by cosinor analysis in each of 4 Phases: pre-endophyte (P1), endophyte exposure, pre-LPS (P2), post-LPS spike 1 (P3), post-LPS spike 2 (P4). During P1 of E1, amplitude (P=0.05), but not mean temperatures (P>0.10), differed across days (P=0.05). Endophyte affected E2 vaginal temperature amplitudes in P2 (P=0.07) and P4 (P=0.08) without influencing mean temperatures. Significant treatment*weaning exit velocity (wEV) interactions occurred for E2 mean rectal temperatures during P1-P3 (P≤0.10). During E1, post LPS, endophyte depressed glucose (P=0.05) and increased creatinine (P<0.01) and decreased TNF-α (P<0.01) at 24h. During E2, post-LPS, IFN-ɤ decreased (P=0.02) with increasing wEV. Endophyte increased serum BUN concentrations with slow wEV and increased BUN with fast wEV (P=0.04) post-LPS in E2. Endophyte increased NEFA (P<0.01) and IL-6 (P=0.02) from 1-8 hours post-LPS during E2. Results demonstrate modulation of CRT and APR by both endophyte and wEV, and demonstrate effectiveness of cosinor analysis in detecting CRT responses.

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