If applied properly, hay preservatives inhibit mold and may permit baling at greater than 20% moisture. That can reduce field drying time and leaf loss during baling, says J.W. Schroeder, North Dakota State University Extension dairy specialist.

The two most commonly used types of preservatives for high-moisture hay are bacterial inoculants and propionic acid-based solutions. “At present, responses to hay inoculants are quite variable. Additional research and development are necessary before hay inoculants offer the degree of economic benefit noted for silage inoculants,” says Schroeder.

For propionic acid to be effective, correct levels must be used, he says. At least 1% propionic acid is needed to preserve hay with 32% moisture. Propionic acid solutions vary from 10 to 100% propionic acid. Schroeder doesn’t recommend using very diluted products because larger volumes of water are applied to the crop.

“Why add more water to your already wet hay?” he asks.

Depending on the product and application rate, treating with propionic acid-based products will cost from $5 to $20 per ton of hay. The increase in leaf retention seldom pays for the additive, he says.

“However, acid preservation may be most beneficial when the producer is faced with potential loss from rain damage. Uniform distribution of propionic acid is important because “pocketing” of molds (only parts of the bale being moldy) has been observed.”

If this spring’s wet weather continues, he anticipates more interest in hay preservatives this year.