If the pigs‘ bodies turned down their own cortisol production, I would assume that their endocrine system considered the level as too high, or it wouldn’t compe

If the pigs‘ bodies turned down their own cortisol production, I would assume that their endocrine system considered the level as too high, or it wouldn’t compensate. Cortisol has its place, but it‘s timed (usually with a spike at around 6AM, and after exercise) and excess can lead to bad sleep quality and worse. Low cortisol also does not at all mean that stress is low within cells. If you put a strain on e.g energy production within mitochondria, you will get a lot of cellular stress (accumulating nitric oxide) that is not directly related to cortisol. Cytokines would be another factor - stress leads to inflammation. There might be enough cortisol around in those pigs to suppress inflammation, but it doesn’t mean they are low on stress.