I must have piggies because then really clean it up as long as I have the hay ring. Without the ring they end up using it for bedding.
As to the mention of chronic cough and respiratory issues - that is directly linked to the quality of hay. You should only use hay from someone who knows how to cure and bale it for horses and keeps it stored under shelter. They can take shortcuts for cattle hay and keep it stored out in the field but that is begging for problems when it comes to horse hay.
True. But a wet spot in a bale can happen, and cannot be easily seen in a big roundbale. Once mold develops in there, it's not only what you can see as moldy, but the spores go about 10" in the visibly good part. Plus, even hay stored under tarp can go moldy.