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Options for wet hay outlined

by Wyoming Livestock Roundup

Nebraska Extension Educators Hannah Greenwell Smith, Ben Beckman and Connor Biehler address concerns and offer solutions for hay with high moisture content in the latest University of Nebraska-Lincoln (UNL) Aug. 1 BeefWatch newsletter.

As most parts of the West continue to receive rain, hay producers had to quickly adjust from dry conditions to extremely wet weather this year. 

Hay that gets rained on while still in the windrow will lose nutritional value, and if it’s put up too wet or has been sitting in water, it will need special consideration.

Hay combustion

The UNL educators explain a major concern with wet hay is hay combustion. 

When hay is baled above 20 percent moisture content, plant tissue begins to break down through microbes and mold begins to grow. This biological activity creates heat and the possibility of combustion.

“If producers end up with hot hay too wet to bale, store it away from other bales and outside to limit the risk of fire spreading,” the team advises. “Bale combustion can begin at temperatures as low as 190 degrees Fahrenheit, especially in coarse hays like sorghum-sudangrass hybrids.” 

The educators further note coarse-stemmed bales allow for greater oxygen flow, which elevates the risk for combustion, and moving hot bales could increase oxygen flow through the bales, providing fuel for combustion.

The UNL team advises producers to check temperatures periodically on wet hay bales by using a long-stem compost thermometer or driving a metal pipe into the bale and dropping in a nonmercury thermometer attached to a string. 

Bales at 170 degrees Fahrenheit or higher should be closely monitored as heating will continue to occur when they reach this temperature.

Mold and mycotoxins

However, if hay bales do not get to the point of combustion, they will continue to decline in quality. 

“Mold growth uses plant tissues as an energy and protein source,” the team of educators explain. “Hot temperatures denature cell structures, which changes proteins and carbohydrates, making them unavailable for animal digestion.”

Mold can produce mycotoxins which can be deadly to animals if the levels are high enough. 

The educators state, “The best way to use moldy hay is to spread out the bales and let the animals pick through it, with a second source of clean hay for them to select from as well. Mold often reduces palatability, and animals will avoid especially bad chunks.”

Testing hay will be important this year, as hay quality is vital for meeting nutritional needs for animals to sustain through the winter. As bales cool off and moisture content decreases, hay quality will also decrease.

Options for wet hay

“If weather conditions do not allow for hay to dry and cure, baleage or other high-moisture harvesting techniques can be an option,” the educators advise. 

Baleage is similar to traditional dry hay because it can be put up in a square or round bale, but baleage is traditional hay which is too wet to store safely and it is wrapped or sealed in plastic.

Baleage can be fermented as individual bales or in a tube or inline.

Iowa State University Extension and Research suggests wrapping wet hay as soon as possible after baling to decrease nutrient loss. Adding silage film to the bale will stop the loss of nutritional value because it’s not exposed to sunlight except for the outside edges. 

According to North Dakota State University research, preserving forage by ensiling it under anaerobic conditions may be an alternative. But if producers cannot, they can preserve forage by spraying it with organic acids as it is harvested. 

Preservatives can reduce the growth of aerobic microbes in wet hay, allowing the hay to be baled at a higher moisture content.

However, hay preservatives do not improve nutritional quality. They prevent deterioration of quality caused by excessive aerobic microbial action by heat buildup.

Melissa Anderson is the editor of the Wyoming Livestock Roundup. Send comments on this article to

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