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.
Objective—To determine the effect of dietary supplemental lipoic acid (LA) on serum concentrations of metabolic hormones and acute-phase proteins of steers challenged with infectious bovine rhinotracheitis virus (IBRV).
Procedures—Steers were randomly assigned to 4 treatments: negative control (NC; no LA, no IBRV challenge), control (CON; no LA, IBRV challenge), 16 mg of LA/kg of body weight (BW)/d plus IBRV challenge (LA16), and 32 mg of LA/kg of BW/d plus IBRV challenge (LA32). Following a 21-day adaptation period, CON, LA16, and LA32 steers received IBRV (2 mL/nostril [day 0]); NC steers received saline (0.9% NaCl) solution. Blood samples, nasal swab specimens, BW, and rectal temperatures were obtained 0, 1, 3, 5, 7, 14, and 21 days after challenge. Serum was analyzed for concentrations of haptoglobin, amyloid-A, leptin, and anti-IBRV antibodies.
Results—Steers fed LA32 began gaining BW by day 7, whereas BW of CON and LA16 steers declined. Serum haptoglobin concentration of LA32 steers was lower than that of CON and LA16 steers on day 7. Serum neutralization titers for 30 of 32 steers were negative for anti-IBRV antibodies before challenge; however, all steers (including NCs) had antibodies on day 21.
Conclusions and Clinical Relevance—Results suggested that LA supplementation augmented certain aspects of the immune response; LA32 steers had a more rapid recovery from IBRV viral challenge than did others.