Location: Livestock Issues ResearchTitle: Functional capacities of blood neurtrophils are influenced by both acute and chronic dexamethasone stress models in beef steers Author
|Ballou, Michael - Texas Tech University|
|Carroll, Jeffery - Jeff Carroll|
|May, Nathan - West Texas A & M University|
|Roberts, Shelby - West Texas A & M University|
|Hughes, Heather - West Texas A & M University|
|Sharon, Kate - Texas Tech University|
|Richeson, John - West Texas A & M University|
Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: 3/22/2015
Publication Date: 7/1/2015
Citation: Ballou, M.A., Carroll, J.A., Sanchez, N.C., May, N.D., Roberts, S.L., Hughes, H.D., Broadway, P.R., Sharon, K.P., Richeson, J.T. 2015. Functional capacities of blood neurtrophils are influenced by both acute and chronic dexamethasone stress models in beef steers. Journal of Animal Science Supplement. 93 (E-Supplement 3):20,Abstract#M37.
Technical Abstract: This study investigated the effects of acute and chronic stress models on the functional capacity of blood neutrophils in beef steers. Steers (N=32; 209 +/- 8 kg) were blocked by BW and assigned to 1 of 3 treatments: 1) Control (CON), no dexamethasone (DEX); 2) Chronic stress (CHR), 0.5 mg/kg BW DEX administered intraveneously at 1000h on day 3 to day 6; or 3) Acute stress (ACU), 0.5 mg/kg BW DEX administered intraveneously at 1000h on day 6 only. Multiple blood samples were collected from jugular catheters to profile hematology. A blood sample collected at 2 hours after the 4th DEX injection in the CHR treatment and 2 hours after the only DEX injection in the ACU treatment was analyzed for functional capacities of neutrophils, which included: surface expression of L-selectin (CD62-L) and the phagocytic and oxidative burst capabilities to an environmental Escherichia coli. There was a treatment x time interaction (P=0.001) for neutrophil concentrations in peripheral circulation. The concentration of neutrophils increased 24 hours after the 1st DEX injection among the CHR steers when compared to CON (10.6 vs. 2.8 +/- 0.62 x 10^6 / mL; P=0.001) and remained greater until 72 hours after the 4th DEX injection. Neutrophil concentrations also increased rapidly, within 2 hours of the DEX, in the ACU steers. Treatment influenced (P=0.001) the expression of L-selectin on the surface of neutrophils (119^a, 138^b, and 61^c +/- 5.2 MFI) for CON, ACU, and CHR steers, respectively. The percentages of neutrophils phagocytizing and producing an oxidative burst were suppressed (P=0.001) among the CHR steers only (72^a, 71^a, and 55^b +/- 4.2%), whereas the intensity of the oxidative burst was suppressed (P=0.001) for both ACU and CHR steers (170^a, 131^b, 63^c +/- 11.7 MFI) for CON, ACU, and CHR steers, respectively. In contrast, the intensity of neutrophil phagocytosis was not influenced by treatment (P=0.439). These data indicate that chronic DEX suppresses neutrophil L-selectin as well as neutrophil phagocytosis and oxidative burst, whereas the acute DEX may initially prime neutrophil L-selectin expression although the oxidative burst intensity was already partially suppressed.