When baling hay a little too wet to store well, two types of additives can help – hay inoculants and hay preservatives.
Legitimate hay inoculants contain bacteria and sometimes ingredients like yeast and enzymes that reduce growth of microorganisms that cause hay to mold and spoil. Make sure to use hay
inoculants, not silage inoculants that rarely work on hay.
Inoculants work best when baling hay at the highest possible moisture for safe storage without additives. But since windrows have uneven moisture and our estimates of moisture aren't always perfect, inoculants often protect against small errors and allow you to bale hay that is 3 to 5 points higher in moisture than would normally store safely. But no higher! All inoculants tested in University controlled studies failed frequently when moisture of hay was over 25 percent.
Tests show that the only products that permit consistent, reliable, safe baling of hay that is definitely too wet to bale are organic acids like propionic and acetic acid. Although these acids are more expensive than inoculants, when applied uniformly at correct rates to work properly, they do work.
Acid-treated hay still will heat some and become discolored, but most feed value will remain protected. Also, be sure to use the buffered forms of these acids to reduce the corrosion and odors that come from straight acids.
If rain often affects your hay making plans, hay inoculants and
preservatives might be worth looking into. (SOURCE: Bruce Anderson, Extension Forage Specialist, University of Nebraska)