Technical note: Bovine acute-phase response after corticotrophin-release hormone challenge

The objective of this study was to evaluate plasma concentrations of cortisol, acute-phase proteins, and proinflammatory cytokines in beef steers after an intravenous corticotrophin-release hormone (CRH) infusion. Six weaned, halter-trained Angus steers (BW = 163 ± 7.0 kg; age = 203 ± 5.8 d) were fitted with indwelling jugular catheters on d -1 of the study and assigned to receive intravenously 0.1 μg of bovine CRH/kg of BW on d 0 of the study. Blood samples were collected every hour via jugular catheters from -1 to 8 h, and every 6 h via jugular venipuncture from 12 to 72 h relative to CRH infusion (0 h). Steer rectal temperature was assessed concurrently with each blood collection. Samples collected from -1 to 8 h relative to CRH infusion were analyzed for plasma concentrations of IL-1β and IL-6, tumor necrosis factor-α, interferon-γ, cortisol, ceruloplasmin, and haptoglobin, whereas samples collected from 12 to 72 h were analyzed for plasma concentrations of ceruloplasmin and haptoglobin only. Plasma cortisol concentrations were greater (P < 0.01) at 1, 2, and 3 h compared with prechallenge values (2.8, 2.3, 13.9, 8.2, and 5.7 ng/mL for -1, 0, 1, 2, and 3 h, respectively; SEM = 0.6). Mean postchallenge IL-6 concentrations were greater (P = 0.04) compared with mean prechallenge values (1.49 vs. 1.34 log pg/mL; SEM = 0.05), whereas IL-6 concentrations at 6 h were greater (P ≤ 0.05) compared with prechallenge values (1.36, 1.33, and 1.61 log pg/mL at -1, 0, and 6 h, respectively; SEM = 0.09). Rectal temperatures were greater (P < 0.01) at 2 and 8 h compared with prechallenge values (38.9, 39.0, 39.3, and 39.5°C at -1, 0, 2, and 8 h, respectively; SEM = 0.07). Plasma ceruloplasmin concentrations were greater (P = 0.03) at 54 h (29.6, 31.5, and 35.2 mg/dL at -1, 0, and 54 h, respectively; SEM = 1.7), whereas plasma haptoglobin concentrations were greater (P < 0.05) at 54, 66, and 72 h compared with prechallenge values (3.3, 2.8, 4.3, 4.6, and 4.1 absorbance at 450 nm × 100 at -1, 0, 54, 66, and 72 h, respectively; SEM = 0.24). In conclusion, intravenous CRH infusion at 0.1 μg/kg of BW increased circulating concentrations of cortisol and stimulated the acute-phase response in halter-trained beef steers.