Hormone and metabolite changes with stress in stress-susceptible pietrain pigs

Pigs of the stress-susceptible Pietrain breed, weighing about 60 kg liveweight, were fitted with indwelling jugular vein catheters which were exteriorized between the shoulders to allow stress-free blood sampling. After surgery, the animals were placed in metabolism crates and allowed at least seven days to recover and to become accustomed to handling, and to their environment, before experimentation. On the day of study, the pigs were subjected to a stimulated loading stress. Blood samples were taken both before, and a number of times after, the stimulated loading procedure. Plasma levels of: glucose, insulin, lactate, and thyroxine rose rapidly to peak levels at 10 min after simulated loading. Cortisol and triiodothyronine rose to peak levels 15-20 min after the stressor was applied, while free fatty acid levels were initially depressed, but later showed a rise at 120 min. From these results it seems that plasma cortisol, thyroid hormones and lactate concentrations may prove to be useful indicators of stress, either individually or in combination.