Year of Publication

2015

Degree Name

Master of Science (MS)

Document Type

Master's Thesis

College

Agriculture, Food and Environment

Department

Animal and Food Sciences

First Advisor

Dr. Eric S. Vanzant

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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