(quoted from post at 04:16:03 07/04/17) I think of rain and hay like tea leaves. If they are green (fresh cut hay) and get rinsed, no tea. If they get dried out (hay that is ready to bale),
and rinsed, then you got tea (hay with less nutrients).
As far as dust, there is dirt/ash from getting into your hay from your tines, disc mower, etc into the dirt which I'm told can increase the hay's iron
levels. I have a horse customer that has an IR horse and issues its high iron. So low ESC+starch and low iron levels are important. Our high
stubble cut helps eliminate the iron issue. However, soaking the hay will bring down the sugar and iron levels, but is a pain for the owner. If
you are testing your hay, you get some rain and can keep it from dust molding in the windrow, you might have hay suitable for an IR horse.
Mold dust - you can smell it vs mechanical/dry hay.
As far as baling early avoid to rain, without having dust or mold issues, I'd highly recommend a hay preservative/applicator on your baler. We
have a buffered propionic acid system on our baler ready to go, but haven't used it - yet. Also recommend a baler mounted moisture meter.
We have an Agtronix BH-2 moister meter and it gives live readings so we know exactly where the moisture levels are throughout the day.
Since we installed it, where the humidity levels of the hay were in range, even though I would have guessed it might be dusty, zero dust. If the
levels get borderline we stop baling or have our preservative applicator we can use if we choose. Our Hesston 1110 mower conditioner - the
conditioning effect has been a game changer here in the mountains of VA.
Bottom line - I think you can make horse quality hay, even with rain or the threat of it.
Good luck,
Bill