[Beaker]

As long as they are used to grass, it shouldn't be a problem. It's only if you throw a horse out on a field who isn't used to grazing 24/7. But even starting them out again, I'd be careful.

[CindyDawg]

It shouldn't be a problem if they are just penned up a few days for bad weather though should it?

[Beaker]

Based on this article I found, the colic will develop before the founder because the founder takes a couple of days or weeks in order for the symptoms to be noticed. I found it on equisearch