Yes, I can certainly share it with you. I'm no expert in the reproductive cycle of hogs, but that's right, there are phases in the production cycle where typically the hog would be in a gestation crate.
It's as much as anything to ensure the well-being of the animal. Hogs will tend to fight. They will be in conflict sometimes. Dominant hogs can end up getting all the food, so having a stall system is a way to manage their health and welfare and ensure they all get adequate nutrition.
Then at the point when a sow has its piglets, protecting the piglets from the mother is actually necessary, because the piglets can be crushed.
So it's a system that achieves those outcomes. That's why I say it's not as simple as saying provide open housing, because then you can get into competition. You have to look at systems of electronic feeding, and access to stalls during feeding so that there is no competition for food, for example. These are some of the factors that would distinguish those.