South Dakota State Extension Service provided some hay storage tips at beefproducer.com that may help protect your investment in hay. Dr. Karla Hernandez indicates hay storage losses are around 5% when hay is harvested at 15% moisture and stored under dry conditions. However, nutrients can be lost if hay is not stored properly and can occur if moisture exceeds 20%. Every step in the process from cutting to baling to hauling can lead to loss, and a lot of these losses are mechanical or weather related.
Round bales have increased losses compared to square bales because they are usually stored outside and are uncovered. You can decrease spoilage by making the bale denser, and the density of round bales should be a minimum of 10 pounds of hay per cubic foot. When making windrows for baling, attempt to make uniform size windrows and match the size of the windrows to the specific recommendation of the bailer you are using.A uniform windrow allows a uniform bale and a denser bale. Also, it may be worth considering erecting a pole barn or similar structure to store round bales; the money saved by decreasing losses may be enough to pay for the barn.
As far as storing bales, large round bales should be stored in rows with the sides not touching to avoid a higher amount of moisture in them. Dr. Hernandez recommends that rows of round bales should be lined up north to south to allow more hours of exposure of the round bales' sides to the sun. When lining up round bales in a row, allow a minimum of 3 feet between rows to allow sunlight to penetrate and air to circulate. Hay is expensive and hopefully by using these tips, you can avoid some of the common losses of hay.