Evaluation of the inter-relationships of temperament, stress responsiveness and immune function in beef calves
A series of in vivo and in vitro approaches were followed to assess the inter-relationships of temperament, stress responsiveness and immune function in beef bulls and steers. In experiment one, Brahman bull calves were weaned at approximately six months of age when pen score and exit velocity were measured to sort calves into groups with extremes in temperament (calm n = 10 and temperamental n = 10). The calves were vaccinated on day 0 and 42 of the study with serial blood samples colleted for 11 weeks. Calm calves tended to have higher primary and secondary immune responses as indicated by increased serum concentrations of immunoglobulin G following Clostridial vaccination. In vitro lymphocyte cultures were performed on day 0 and 42 to measure proliferation and IgM production. Calm calves had significantly higher proliferative responses on both day 0 and 42. Lymphocyte IgM production was significantly higher in calm calves on day 0 and tended to be higher on day 42 than temperamental calves. In experiment two, weaned and yearling steers were arrayed by pen score and exit velocity, to assign steers to groups with extremes in temperament (trial 1: calm n = 7 and temperamental n = 5; trial 2: calm n = 5 and temperamental n = 5). In both trials, temperamental steers had higher proliferative responses than calm steers. Immunoglobulin M production did not differ in either trial. The effects of stress responsiveness on animal performance and health are considerable because they affect the profitability of the cattle industry. Investigations into animal temperament can help cattle producers identify animals that may be more susceptible to decreased performance and immunosuppression. The effectiveness of vaccines given to calves is important in conferring immunity to common diseases at times when they are at a higher risk for infection. If we can identify temperamental animals that will not perform as well as their cohorts, management procedures can be altered to reduce the risks associated with decreased performance and morbidity.