Evaluation of endocrine and immune responses of steers challenged with infectious bovine rhinotracheitis virus.

Objective: To evaluate the endocrine and immune responses of steers challenged with infectious bovine rhinotracheitis virus (IBRV).

Animals: 12 crossbred beef steers.

Procedures: Steers were randomly assigned to IBRV- (control) or IBRV+ treatment groups. Experimentally challenged steers (IBRV+) received a dose of IBRV intranasally (8.0 50% tissue culture infective doses), IBRV- steers received a saline (0.9% NaCl) solution placebo intranasally, and each group was placed in an isolated paddock. At 72 hours after challenge, all steers were fitted with indwelling jugular catheters and placed into individual stanchions. Blood samples were collected on days 4 through 8. Serum was analyzed for concentrations of cortisol, interleukin-6, interferon-γ, tumor necrosis factor-α, growth hormone, and insulin-like growth factor I.

Results: From 72 to 144 hours after challenge inoculation, the IBRV+ group had significantly greater mean rectal temperature, compared with the IBRV- group; the greatest temperatures in both groups were observed at 72 hours. Serum cortisol concentrations were increased in both groups from hours 72 to 136 and serum interferon-γ concentrations were greater in the IBRV+ from 94 to 112 hours after inoculation. Growth hormone concentration was greater in the IBRV+ group at various time points, but no difference in insulin-like growth factor- I concentration was observed.

Conclusions And Clinical Relevance: Results indicated that IBVR challenge altered growth hormone concentration at some time points but was not associated with large increases in circulating proinflammatory cytokines.