Thanks for your experience with Cory. Sounds like he is very sensitive to different species. I am unable to experiment with different hays due to location.
Since Lad seems to do okay on average 28 days per month, with sloppy manure on the other days, I think the problem may not be with the mixed grass hay.
Is this common with PPID?
Has anyone tried pre-and/or probiotics as preventative?