Peripheral concentrations of cortisol as an indicator of stress in the pig

Twenty-four crossbred gilts (7 to 9 months old) were exposed to 3 different stressors to evaluate changes in peripheral concentrations of the adrenal hormone cortisol. Gilts were confined in a box for 1 hour, electrically stimulated for 6 minutes, or heat-stressed for 6 hours; these stressors were imposed for 3 consecutive days. Blood samples were collected repeatedly, and serum cortisol concentrations were determined by radioimmunoassay. Peak cortisol concentrations for pigs in the box, electrically stimulated, and heat-stressed were 67.8 +/- 9.9 ng/ml (mean +/- SEM), 43.2 +/- 5.8 ng/ml, and 25.2 +/- 3.0 ng/ml greater than the control concentrations. The times at which these peaks occurred varied with each stressor. Overall serum cortisol concentrations decreased from day 1 to day 3, but the response to a given stressor was not diminished. Our data substantiate the use of cortisol as an indicator of stress in swine and emphasize consideration for the interval between exposures to stressors.