ROYALTON, Minn. – Rainfall is a double-edged sword, especially for hay production. Rain grows hay, makes tonnage, but it also leads to issues with storage and quality.

“I think moisture was a bigger issue this year than previous,” said Derek Wawack, on-farm specialist with Alltech, during a recent phone interview. “Mold, especially decaying type molds, get really bad in these wet years.”

There are several species of mold and fungi that are naturally occurring in the field. They need only the right conditions to get on the plants, proliferate and cause damage. Heavy rains that cause dirt to splash up onto the leaves and stem is a perfect example of how molds get into a hay crop.

“There’s a lot of soil contaminants that could splash on a plant that will definitely cause some problems,” said Wawack. “That could be molds, yeasts, mycotoxins. Areas that do get a lot of splashing rain usually see a lot of yeast once in storage.”

Once the hay is down, in a windrow, moisture and heat can create a perfect environment for these molds to grow. Interestingly enough, at this stage, those molds are not producing the mycotoxins that are thought of when thinking about contaminated hay.

“You keep mold in an environment where it wants to keep growing and thriving, it will never get mad and it will never want to go on a defense mechanism and form of mycotoxins, so happy mold will never really make mycotoxins,” he said. “Stressful mold, angry mold will make mycotoxins.”

When those molds are moved into an anerobic environment for storage, i.e. dry, packed bale, haylage pile or bag, the mold species get stressed as that is not an environment they like to be in. That is when the mycotoxins start to form.

“Let's say slightly wet to dry hay, acid treatments are going to be a huge help,” he said. “You are going to kill off mold that maybe came out of the field already. That could cause stress, which could form mycotoxins, but the levels hopefully are so low that it's not going to cause any issues.”

Feeding hay that has mycotoxin contamination is risky, but it really depends on the species of animal and the amount of toxins.

Ruminants, for example, are able to consume greater levels of mycotoxins than other species without suffering negative consequences. Of course, there is a limit. Too much of any toxin over time to an animal will cause issues.

“Dilution is the solution in the feed world, that is a great saying,” he said. “You can dilute it down to the point where hopefully it doesn't cause any harm, especially in a ruminant.”

Alltech produces a feed guide, Mycotoxin Management, that can help growers better understand the levels of specific types of mycotoxins that can be fed to various types of livestock. That guide can be found at

In an effort to raise awareness among livestock producers about the potential for mycotoxins in their feedstuffs, Alltech is offering a free 37+ test. The 37+ test will test a feed sample for 50 types of toxins. Information regarding the promotional free test can be found at

According to the Alltech laboratories, 44.4 percent of 2018 hay and haylage samples tested from Minnesota, North Dakota, South Dakota, Wyoming and Montana had toxin levels that would be considered high risk when fed to beef cattle. Less than a quarter of the samples, 22.2 percent were low risk and the remaining samples were moderate risk.

Depending on the type of mold and the way it was stored, mycotoxins might not be the main concern.

“The molds themselves can cause problems, said Wawack. “Whether it's growth rates, intakes, or abortions. There are certain types of molds that will cause fungal abortions, some can cause early embryonic death.”

Testing for mycotoxins in feedstuffs is important, especially during the wet years, but visual observations are also key.

“If you got a bale that maybe has an end that's moldy or a part of it that's molded, you got to either fork that off or cut it off,” he said. “You are going to play a safer game by cutting that off and feeding the cleaner side.”