Hoda Nikpour

Date of Graduation

2017

Document Type

Thesis

Degree Type

MS

College

Davis College of Agriculture, Natural Resources and Design

Department

Animal and Nutritional Sciences

Committee Chair

Robert A Dailey

Committee Co-Chair

Scott Bowdridge

Committee Member

Ida Holaskova

Abstract

Wethers and ewes were used to study the effect of catheter or repeated venipuncture on circulating cortisol and leukocyte concentrations and physical behaviors following administration of lipopolysaccharide (LPS), a gram-negative bacteria cell wall component. Animals were injected with LPS or saline, as a control, to induce an innate immune system response. In addition, blood leukocytes and cortisol levels were studied to determine the effect of sex on immunological and stress responses. Thirty-eight mature Dorset and Suffolk wethers and ewes were assigned into one of four treatment groups: 1.) no-catheter + LPS treated ewes (n=5) and wethers (n=4) that were restrainted to draw blood from the jugular vein; 2.) no-catheter + saline treated ewes (n=6) and wethers (n=4) restrained to draw blood from the jugular vein; 3.) catheter + LPS consisting of LPS-treated ewes (n=6) and wethers (n=4) in which a jugular catheter was placed to draw blood; and 4.) catheter + saline treated ewes (n=6) and wethers (n=4) with a jugular catheter. Blood was collected from the jugular vein catheter, which was placed into the jugular vein the day before the experiment and anchored with a stitch to secure it or venipuncture before the challenge followed by post challenge samples every 30 min for 3 h and every hour until 12 h, and once at 24 h. Physical behaviors and rectal temperatures were monitored before LPS administration and every hour for 12 h post challenge. Total white blood cell counts and leukocyte differentials including lymphocytes, monocytes, and granulocytes were measured immediately after collection using a veterinary hematology blood analyzer (Abaxis VetScan HM5, Abaxis Inc.), and remaining samples were centrifuged, and plasma was collected and stored at -20°C until concentration of cortisol was determined by ELISA. Treatment with LPS resulted in increased cortisol concentrations, rectal temperatures, lethargy, and nasal discharge, as well as decreased WBC count and appetite in ewes and wethers. Catheter insertion alone resulted in increased WBC count, but did not affect cortisol. However, a significant increased in cortisol occurred in LPS treated sheep fitted with catheters compared to those without. Rectal temperatures during LPS challenge were greater in wethers than ewes, and a greater decrease in total WBC count and leukocyte differentials was seen in ewes when compared to wethers. Moreover, there was no significant effect of sex on cortisol concentrations. In summary, there were no differences in cortisol concentrations between sexes and no significant effect of the catheter alone. However, during the LPS challenge catheter exacerbated the innate immune response and cortisol levels, and rectal temperature and WBC count were affected by sex. Therefore, catheter placement created an additional stressor that augmented the LPS-induced immune response.

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