Valuable indicators of physical stress in porcine plasma.

Various markers for stress were evaluated in the plasma of pigs. Treadmill exercise was chosen as a well defined and quantifiable stressor. One group of non-stress-susceptible pigs had to carry out two intense exercise bouts at a one-week interval, and another group remained in their pens and served as controls. Large interindividual differences in the performance and in the hormonal and metabolic responses to exercise were observed. The exercise stress resulted in an immediate increase in the plasma concentrations of cortisol, lactate and hypoxanthine, with a return to the pre-exercise levels within one hour. No direct effect of physical stress on CBG binding capacity or on the concentrations of xanthine and uric acid was observed. In two very nervous pigs, even mild stress in connection with the first blood sampling resulted in an elevated concentration of lactate, but the cortisol and hypoxanthine values remained at the basal level. It is concluded that plasma concentrations of cortisol, lactate and hypoxanthine are valuable markers for physical stress.