|MAY, NATHAN - West Texas A & M University|
|Carroll, Jeffery - Jeff Carroll|
|ROBERTS, SHELBY - West Texas A & M University|
|HUGHES, HEATHER - West Texas A & M University|
|SHARON, KATE - Texas Tech University|
|BALLOU, MICHAEL - Texas Tech University|
Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: 3/22/2015
Publication Date: 7/1/2015
Citation: May, N.D., Carroll, J.A., Sanchez, N.C., Roberts, S.L., Hughes, H.D., Broadway, P.R., Sharon, K.P., Ballou, M.A. 2015. Comparative efficacy of dexamethasone or corticotropin releasing hormone and vasopressin administration as a model to induce chronic physiological stress in beef cattle. Journal of Animal Science Supplement. 93 (E-Supplement 3): 420-421, Abstract#T309.
Technical Abstract: The objective of this study was to delineate a model for chronic stress by evaluating physiological and hematological alterations in cattle administered: 1) 0.5 mg/kg body weight dexamethasone (DEX) once daily at 10am for 3 days consecutively, or 2) 0.3 micrograms/kg body weight corticotropin releasing hormone (CRH) and 1 microgram/kg BW vasopressin (VP) twice daily at 10am and 10pm for 3 days consecutively. Twelve (n=6/treatment) weaned beef steers (BW=389 +/- 11kg ) were stratified by body weight, assigned randomly to treatment, and fitted with indwelling rectal temperature (RT) devices and jugular catheters, prior to relocation into individual stanchions in an environmentally-controlled facility. Blood samples were collected at 0.5-hour intervals from -2 to 6 hours relative to each 10am challenge. Serum was isolated and stored at -80C until analyzed for cortisol concentration. A whole blood sample was evaluated immediately following collection times to profile hematological responses via automated hemocytometer. A treatment × time interaction (P<0.001) was observed for RT, which increased transiently in both treatments following the 10am challenge time each day. However, the magnitude of the febrile response was greater (P<0.001) for DEX. Likewise, serum cortisol increased transiently in response to both challenges, yet the cortisol increase was more pronounced for CRH-VP (treatment × time; P<0.001). Total peripheral blood leukocytes (PBL) were increased in both treatments; however, the PBL concentration was greater for DEX vs. CRH-VP from hour 5 to 54 (treatment × day; P<0.001). The total PBL was associated with a corresponding increase in circulating neutrophils observed for DEX on days 2 and 3, but not CRH-VP (treatment × day; P<0.001). In contrast, eosinophils decreased (P<0.001) sharply for DEX on day 1 and remained undetectable through day 3. These comparative data suggest that exogenous administration of both DEX and CRH-VP alter RT and cortisol variables indicative of stress, while DEX may more strongly inhibit neutrophil translocation from peripheral blood, a key component of stress-induced immunosuppression.