Ugh we just had 7 inches Monday night and then 8 inches just a few days before that. The last time we hit 60 degrees was over 5 months ago. Wish we had green grass right now or just grass, it can still be brown and dead I just want to see it.
Does either horse have a history of metabolic problems? Has either horse foundered in the past? Is either horse obese or have a big cresty neck? Any of these problems would put a horse at risk of foundering on one grass binge. All others I would not worry about.
I'd say "no" to all (but not sure about "big cresty neck" - my paint doesn't for sure, but I'm not positive about my qh (see pic)).
And thanks, Cherie! Yes, mine are mostly on good quality timothy hay, and (according to my mom) they cleaned up most of their night hay before we found them out on pasture. So hopefully they were quite full.