Although hay can keep quite well for several months in a well ventilated, covered hay loft or barn, it is can also be prone to mold. Or, it can become excessively dry and dusty. These conditions can cause your horse to turn up his velvety nose at dinner time or worse–develop a chronic respiratory condition called “heaves.”
The dry, nagging cough and raspy breathing associated with heaves is related to your horse’s response to dust and allergens in the hay. So when you open a bale of hay this winter, look to see if poufs of visible dust erupt from the flakes. Do you want to breathe that?
Also, check for mold. When hay is cut too green, then baled and stored, it can mold deep within the flakes. Take a whiff of the hay. Although it probably won’t smell like sweet springtime feed, it should never smell acrid or mildewy. If it does, toss it out. While feed may be expensive, it’s still not as costly as a colicky horse.
thanks for the info.