Preservatives Can Aid Quality Hay Storage - UNL CropWatch, May 11, 2011

Preservatives Can Aid Quality Hay Storage - UNL CropWatch, May 11, 2011

May 11, 2011

The moisture content when hay is baled influences its yield, quality, and storability.

When hay is baled too dry, leaves fall off stems to the ground, reducing both quality and yield of the harvested crop. Hay baled too wet can get moldy, overheat, or even catch fire. Given these extremes, there is a fairly narrow moisture range that results in good hay that keeps well.

Hay can be baled a bit wetter if a preservative like propionic acid is applied as it’s baled. To get good results, it helps to know how it works.

Baled hay naturally contains millions of bacteria and mold fungi. As they consume hay nutrients, these microbes produce heat. The duration and intensity of this heat determines the amount of damage the hay receives.

This heat also forces moisture out of the bale, something we often call “going through a sweat.” Usually, hay gets dry enough that the microbes soon die or go dormant, but if there’s too much moisture, it can overheat or mold can develop.

Preservatives kill many of the microbes which reduces heat production. This gives hay time to dry out naturally, without the “sweat.” As it dries the preservative also vaporizes and disappears. When bales fail to dry properly and are tightly stacked into storage soon after baling, the remaining microbes eventually produce the mold and heat we wanted to avoid. Also, if rain, high humidity, or other sources moisten the hay later, microbial activity can redevelop since the protection from preservatives lasts only a short time.

Preservatives can help make good hay at higher moisture levels but correct management is needed to keep that hay in good shape.

Bruce Anderson
Extension Forage Specialist


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