I have the same problem with my 18 year old gelding. Invariably, when he's on full hay, he gets diarrhea. He eats hay without an issue in late summer, when I start supplementing the grass. But the minute I take him off pasture and he is only eating hay, it starts. The vet recommended finer hay (second cut) so I bought a bunch last year from a completely different field. No change whatsoever. He doesn't like the coarser hay, and prefers the finer hay, but his stool still gets runny. I put him on pre- and probiotics, and digestive enzymes, and it is finally a little better after a few weeks, but not completely resolved. The only thing I can figure is that the grass must have digestive enzymes that help his digestive system work well.
I do give him timothy hay cubes twice a day, and my equine nutritionist has suggested I could just feed him hay cubes, but that would take away his foraging which keeps him busy all day, and I hate to do that.
I'd be intersted to hear if you find a solution, because we struggle with this for weeks on end each fall. It does seem to resolve itself eventually, but not soon enough.
Oh, I also feed psyllium fiber when it gets bad - sometimes that helps. But you're not supposed to feed it all the time, just for a while, then stop.
I do give him timothy hay cubes twice a day, and my equine nutritionist has suggested I could just feed him hay cubes, but that would take away his foraging which keeps him busy all day, and I hate to do that.
I'd be intersted to hear if you find a solution, because we struggle with this for weeks on end each fall. It does seem to resolve itself eventually, but not soon enough.
Oh, I also feed psyllium fiber when it gets bad - sometimes that helps. But you're not supposed to feed it all the time, just for a while, then stop.
