Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 29, 2012
Publication Date: July 1, 2012
Citation: Cooke, R.F., Carroll, J.A., Dailey, J.W., Cappellozza, B.I., Bohnert, D.W. 2012. Bovine acute-phase response following different doses of corticotrophin-releasing hormone challenge. Journal of Animal Science. 90(7):2337-2344. Interpretive Summary: A collabortive study was conducted by scientists from the Livestock Issues Research Unit and the Oregon State University - Eastern Oregon Agricultural Research Center to determine if activation of the stress axis via the infusion of the neurohormone corticotrophin-releasing hormone would alter the acute phase response of cattle. Cattle were fitted with indwelling jugular catheters and rectal temperature monitoring devices to profile both physiological and immune responses of the cattle prior to and after infusion of the neurohormone. As expected, serum concentrations increased rapidly following neurohormone infusion. The data also revealed subtle, but significant, dose-dependent increases in serum concentrations of tumor necrosis factor-alpha and haptoglobin. Neurohormone infusion also resulted in dose-dependent increases in tissue mobilization, as indicated by circulating concentrations of non-esterified fatty acids, and rectal temperatures. Collectively, these data demonstrate that activation of the stress axis can induce aspects of the acute-phase response in cattle. This information will be of interest to scientists in the field of stress physiology, immunology, and animal health, especially as it relates to understanding the communication pathways between stress and immune function. Additionally, this information should aid in our ability to distinguish between stress induced alterations in the acute-phase response versus alterations due to infection and/or disease in cattle.
Technical Abstract: Fourteen weaned Angus steers (BW = 191 ± 2.1 kg, age = 167 ± 4.7 d) fitted with an indwelling jugular catheter and a rectal temperature (RT) monitoring device were ranked by BW and assigned to receive 1 of 3 treatments (i.v.): 1) 0.1 ug of bovine corticotrophin-release hormone (CRH)/kg of BW (CRH1; n = 5), 2) 0.5 ug of bovine CRH/kg of BW (CRH5; n = 5), and 3) 10 mL of saline (0.9%; n = 4). Blood samples were collected via catheters, relative to treatment infusion (0 h), hourly from –2 to 0 h and 4 to 8 h, and every 30 min from 0 to 4 h. Rectal temperatures were recorded every 30 min from -2 to 8 h. Blood samples were also collected via jugular venipuncture and rectal temperatures assessed using a digital thermometer every 6 h from 12 to 72 h, and every 24 h from 96 to 168 h. All plasma samples collected during the study were analyzed for concentrations of haptoglobin. All plasma samples collected from –2 to 8 h were analyzed for cortisol concentrations. Serum samples collected hourly from -2 to 8 h were analyzed for concentrations of NEFA, IL-6, tumor necrosis factor (TNF)-alpha, and interferon-y. Cortisol peaked at 0.5 h for CRH1 steers, but returned to baseline levels at 1 h relative to infusion (time effect; P < 0.01). In CRH5 steers, cortisol peaked at 0.5 h and returned to baseline levels 3.5 h relative to infusion (time effect; P < 0.01). Cortisol concentrations did not change after treatment infusion for saline steers (time effect; P = 0.42). In CRH1 steers, NEFA concentrations increased and peaked 5 h following treatment infusion (time effect; P = 0.01). Conversely, serum NEFA concentrations did not change for CRH5 and saline steers after treatment infusion (time effect; P > 0.37). Mean serum TNF-alpha concentrations in CRH1 steers after treatment infusion were greater compared to saline (P = 0.02), tended to be greater (P = 0.08) compared to CRH5, and were similar (P = 0.40) between CRH5 and saline steers. Mean RT in CRH1 steers after treatment infusion were greater (P < 0.04) compared to saline and CRH5, and similar (P = 0.50) between CRH5 and saline steers. Haptoglobin increased and peaked 72 h following treatment infusion for CRH1 steers (time effect; P = 0.01), but did not change for CRH5 and saline steers (time effect; P > 0.45). In conclusion, the bovine acute-phase response stimulated by CRH infusion is depended on the CRH dose and the subsequent response in circulating cortisol.