Location: Livestock Issues ResearchTitle: Effects of dexamethasone treatment and respiratory vaccination on rectal temperature, complete blood count, and functional capacities of neutrophils in beef steers
|Hughes, Heather - West Texas A & M University|
|Carroll, Jeffery - Jeff Carroll|
|Roberts, Shelby - West Texas A & M University|
|May, Nathan - West Texas A & M University|
|Ballou, Michael - Texas Tech University|
|Richeson, John - West Texas A & M University|
Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/19/2017
Publication Date: 4/13/2017
Citation: Hughes, H.D., Carroll, J.A., Sanchez, N.C., Roberts, S.L., Broadway, P.R., May, N.D., Ballou, M.A., Richeson, J.T. 2017. Effects of dexamethasone treatment and respiratory vaccination on rectal temperature, complete blood count, and functional capacities of neutrophils in beef steers. Journal of Animal Science. 95:1502-1511.
Interpretive Summary: This study represents a collaborative effort among scientists from USDA-ARS' Livestock Issues Research Unit, West Texas A&M University and Texas Tech University. The objective of the current study was to simulate acute and chronic stress in naïve beef calves via synthetic stress hormone administration and to observe the effects on various health parameters in response to respiratory vaccine administration. The data revealed that administration of a synthetic stress hormone in either an acute or chronic manner suppressed various aspects of immune function, with the greatest suppression of immune function being associated with the chronic administration of the synthetic stress hormone. Based upon our prior research, administration of the synthetic stress hormone in the current study appeared to mimic naturally occurring stressors; however, it is unclear whether or not this model accurately depicts the effects of acute versus chronic stress under field conditions. This model appears to have generated acute and chronic immunosuppression rather than acute and chronic stress. Furthermore, the control group in our study demonstrated the temporal acute phase response following vaccination with an increase in rectal temperature and pro-inflammatory cytokines following respiratory vaccination. Future research investigating the effects of naturally occurring stress conditions on vaccine response and health are warranted. These data will be of interest to researchers and veterinarians working in the field of bovine immunology and stress physiology, as well as cattle producers in general.
Technical Abstract: The objective of this research was to examine the effects of dexamethasone (DEX) treatment on various aspects of immunity following administration of a multivalent respiratory vaccine, using a model intended to mimic acute versus chronic stress. Angus × Hereford steers (n = 32; 209 ± 8 kg) were stratified by BW and randomly assigned to 1 of 3 treatments: 1) Acute stress (ACU), 0.5 mg/kg BW DEX administered i.v. at 1000 h on d 0 only; 2) Chronic stress (CHR), 0.5 mg/kg BW DEX administered i.v. at 1000h on d -3 to d 0; or 3) Control (CON), no DEX. Steers were fitted with indwelling jugular catheters and rectal temperature (RT) recording devices on d -4 relative to vaccination and placed in individual stanchions in an environmentally controlled facility. Blood samples were collected and serum isolated at -74, -50, and -26 h, at 0.5 h intervals from -4 h to 6 h, and at 12, 24, 36, 48, and 72 h relative multivalent respiratory vaccination at 1200 h on d 0. Additional blood samples were used to analyze complete blood cell count (CBC) and functional capacities of neutrophils. There was a treatment × time interaction (P < 0.01) for RT such that DEX treatment in CHR and ACU steers decreased RT on d -3 and d 0, respectively. A treatment × time interaction (P < 0.01) was observed for total white blood cells (WBC), neutrophils, lymphocytes, and monocytes. Specifically, DEX increased WBC and neutrophils in CHR and ACU steers (P < 0.001), yet decreased lymphocytes in CHR steers (P = 0.02) compared to CON steers. Neutrophil concentration increased rapidly, within 2 h of the DEX infusion, in ACU steers. Monocytes transiently increased (P < 0.001) in response to DEX treatment in CHR and ACU steers. In contrast, eosinophils were greater (P < 0.01) in CON than ACU and CHR steers. A treatment × time interaction (P = 0.004) was observed for IFN-', with CON cattle exhibiting greater concentrations than ACU and CHR treatments at 5 h post-vaccination, through d 3. Treatment also influenced (P = 0.001) the expression of L-selectin on the surface of neutrophils. The percentage of neutrophils engaging in phagocytosis and oxidative burst were suppressed (P = 0.001) among the CHR steers only, whereas the intensity of the oxidative burst was suppressed (P = 0.001) for both ACU and CHR steers. These data suggest that our model induced acute and chronic immunosuppression, while defining the acute response to a multivalent vaccine in CON steers.