About the Storage of Propionic Acid Treated Hay
Propionic acid is a hay preservative that a farmer may apply to hay during the baling process. The farmer typically chooses to apply the preservative when the hay cannot be sufficiently dried in the field before being baled. The resulting bales will generally have a moisture content above 18%.
Preservatives containing propionic acid are generally buffered to make the preservative less corrosive.
You might be able to tell if hay is treated with Propionic acid as it may have a sour smell that smells something like vinegar.
One of the things I believe many people (even some farmers) are not aware of regarding propionic acid treated hay is that the bales of hay must be allowed to “cure” to reduce the moisture content in the bales “before” the preservative losses its mold inhibitive effect.
Typically, any hay baled without preservative above 18% moisture will be at risk of some molding. Hay baled above 20% moisture will almost defiantly mold in the bale.
By applying propionic acid the farmer can “temporarily” halt the microbial activity within the bale.
This then gives the farmer the opportunity to essentially “finish” the drying process that would have normally taken place in field, by instead storing the newly baled hay appropriately so that the moisture content of the bale can “sweat out” until the bales reach a moisture level of 18% or less.
The window of opportunity to cure these high moisture bales down to an appropriate moisture level for storage is limited because the preservative tends to dissipate and loose it’s effectiveness after about 4-6 months from the time of baling. http://www.omafra.gov.on.ca/english/...preventing.htm
In other words… Unless each bale of hay is cured to a moisture level of 18% or less within around 4-6 months after baling, the hay may mold (my personal philosophy is to try to get the level moisture level down to 18% or less within one or two months).
I recommend that anyone receiving propionic acid treated bales know what moisture levels those bale are prior to storing.
You can ask your farmer, but what I use is a small hand held electronic moisture tester. The moisture tester has a long probe that you stick in the bale, and it gives the moisture level on a digital display.
The reason I know this is because we lost several hundred bales when we stacked propionic acid treated hay that came directly from the field “tight” in our hay loft. All the hay on the “inside” of the stack molded by mid winter.
The lesson learned is that high moisture bales need to be stacked in a way so they can “breathe”, and the storage area must be well ventilated to allow for the drying of the bales.
May your hay never grow mold…