May 31, 2018

Mycotoxin Mitigation

Erratic weather makes predicting mycotoxin activity hard to predict, but best practices can help limit risk

With ups and downs in the weather in early 2018, it is hard to tell what the future holds for the crop season.

It is the same with mycotoxins.

Mycotoxins, potentially dangerous chemical compounds created by fungi, are found in starchy cereal grains, such as corn, wheat, rye, barley, oats and rice. While they are not typically found in oilseeds, peanuts, ground nuts and cotton seed can also be affected.

Mycotoxins commonly found in grains are aflatoxins, fumonisins and vomitoxin. Ochratoxin A and zearalenone also can cause problems.

Ben Weaver, Eastern regional account manager for EnviroLogix, Inc., Portland, ME, says it was hard to tell what the mycotoxin story for 2018 would be. But he and Erin Bowers, post-doctoral research associate with the Iowa State University Department of

Agricultural and Biosystems Engineering, gave an overall look at what might be seen in the fields this year.

Stored crop status

Weaver says the stored crop from 2017 in Michigan, Ohio, Indiana and Kentucky held up well. He says elevators and processors still conducted some vomitoxin testing because some of the affected 2016 crop was still being blended in. If the grain wasn’t reblended, it couldn’t ship out.

However, Texas, southern Iowa and the southern Dakotas had aflatoxin problems, and there was a fumonisin outbreak in Texas’s corn harvest last year.

Bowers notes that eastern Iowa and further east into the Corn Belt region had some vomitoxin problems, which led to concerns in the ethanol sector. Mycotoxins concentrate in dried distillers grains with solubles at three times the amount in the originating grain.

“Vomitoxin was a big issue when going into swine feed last fall, and increased testing and monitoring of incoming grain was necessary to make sure ethanol producers were putting out safe DDGS for their markets,” Bowers says.

Pat Frasco, director of sales for Milling, Grain and Pet Food for Neogen, Lansing, MI, adds that in order to keep the grain in the summer, managing grain quality is essential.

“On-farm storage inventory will be delivered into grain market during spring and summer, so it needs to be tested before blending in,” he says. “Low prices will keep grain off the market longer so quality risk needs to be monitored.”

Possibilities for 2018

This year, as is true every year, mycotoxin risk is weather dependent.

With only 2% of the crop in the ground in mid-April, it was challenging to determine what mycotoxins would be present in the plants.

“We won’t begin to be able to predict mycotoxin hazards until July,” Bowers says. “We can’t really tell until we know what’s going on during key times for grain, like silking, flowering and grain fill. Weather conditions set the tone for what the risk might be.”

Weaver notes if the cool and wet weather continues, head scab could be a threat. In wheat areas, vomitoxin could become a concern.

“If it clears up and we get normal rain, everything will probably be clean, like it has the last couple of years,” Weaver says.

Late planting dates also place stress on crops. Weaver notes that northern states like Indiana, Ohio and Michigan plant later anyway, but if the weather delays field work until late June or early July, harvest will be a challenge. Corn would attempt to grow in hotter temperatures with less rain. With this increased stress, the crop would be more prone to having toxins and low yield.

“We can get past some of it with genetics and traits, but planting delays and weather variability still can cause challenges,” Weaver says.

Conditions for mycotoxins to thrive

Mycotoxins flourish in varying conditions, depending on the type.

“Each fungus likes its own little niche,” Bowers says.

Aflatoxin thrives in hot drought conditions and is typically found in the southern United States. The Corn Belt doesn’t typically experience aflatoxin unless there is a drought.

Vomitoxin, also known as deoxynivalenol, and zearalenone like cooler, wetter conditions and humidity during the grain fill period.

Fumonisins like warm to hot weather and dry conditions during and after the grain fill period.

Ochratoxin A is a result of problems with storage.

Each fungus that creates a mycotoxin enters the plant in various ways, whether through insects, weather, or other plant damage. Aspergillus fungi, which can result in aflatoxin contamination, travels quickly down the silk channel of corn ears. Fusarium ear rot, which can result in fumonisins, can be associated with insect damage.

In stored grains, mycotoxin-producing fungi can grow and spread if moisture becomes available. Insects or other pests in storage areas also can cause problems by creating hot spots where fungi can grow and potentially produce mycotoxins. Insects and pests also can transfer spores on their bodies as they move within and among storage bins.

Patricia Jackson, market development manager for Vicam, says while molds and mycotoxins are often connected, there can be cases where they are absent from one another.

“One of the mysteries we’ve observed is that molds may be present on a crop or in storage, without the presence of mycotoxins — and we’ve also seen the opposite situation, where no visible mold is observed, but very high levels of mycotoxins are detected,” she says. “Crops tend to have stages of growth where they become more vulnerable to molds and mycotoxins. Research is ongoing to develop strategies for mold and mycotoxin reduction and control from field to storage and throughout processing operations.”

Concerns for animal and human health

The effects of mycotoxins are varied. Aflatoxin is known to cause cancer and childhood stunting in humans. This problem is especially seen in developing countries. Fumonisins are associated with neural tube defects, such as spina bifida, in humans. In animals, they cause problems with health, production and breeding efficiency. In horses, a low level of fumonisins can cause an irreversible disease in the brain that leads to death.

Zearalenone affects the reproductive system of various livestock, causing reduced milk yields, infertility, and other negative effects.

FDA action, advisory and guidance levels lay out maximum levels for certain mycotoxins in feed for various animal species. For example, aflatoxin is considered an adulterant if included in a total mixed ration feed or food product at harmful levels. Corn or grain below 20 ppb of aflatoxin can be used, but there are marketing restrictions. For example, according to the action levels for aflatoxins, corn containing up to 300 ppb of aflatoxin can be used in beef cattle feed. Dairy cows are limited to 20 ppb because aflatoxin can make its way into milk and enter the human food chain.

There also are advisory levels for vomitoxin. Chickens should have no more than 5 ppm in their total diet, while finished feed for swine, which are particularly susceptible to its effects, shouldn’t exceed 1 ppm of vomitoxin.

Treating mycotoxins in grain

While there are no approved methods for detoxifying mycotoxins, blending contaminated grain is still an option for some types of mycotoxins.

“Blending has to be done carefully because sampling for mycotoxins can be difficult,” Bowers says. “It only takes a few contaminated kernels to push a bushel of grain outside an acceptable level.”

Grains that test above 20 ppb for aflatoxins cannot be deliberately blended with clean grain to reduce the aflatoxin level for specific markets without a special waiver from the FDA.

Grain, corn silage and forages also can be treated with various acids or preservatives if mold is identified. Fungicides can help on wheat, although the fungicides don’t necessarily get rid of or prevent a mycotoxin.

“Once a mycotoxin is there, it’s there,” Weaver says.

Mycotoxin mitigation

While weather is still the biggest issue in causing mycotoxins, Weaver and Bowers provided the following tips for mitigating mycotoxins in the field and during storage:

  • Use crop genetics and traits that make a plant more tolerant to various weather and insect challenges.
  • Scout fields for mold, fungi and plant diseases. “If you know you have the mold, the sooner you can harvest, the better. Get it harvested, cleaned and dried down,” Weaver says.
  • Rotate between good and poor hosts for fungi, especially in no-till fields, where fungal spores can remain in the ground and grain stubble and cause problems during the next crop year. Corn-soybean rotations work well because soybeans are not good hosts for fungi that produce mycotoxins.
  • Dry-down properly in a timely manner, making sure to prevent stress cracks.
  • Keep grain dry by ensuring good aeration during storage, inspecting grain bins for any leaks and condensation, and cleaning out grain bins every year.
  • In corn, reduce moisture to 15% in winter and 13% in summer. If mycotoxins are present, drying beyond the normal percentage can help. For example, if a feed should normally be dried down to 15%, decrease the moisture level to 13% to 14%, especially if storing it for a while.
  • Increase the speed of harvesters and ensure proper combine settings when harvesting wheat or corn so that foreign material and damaged grain is not gathered up.
  • Prevent insects and other pests from entering storage.

For elevators, the following tips were given:

  • Develop a monitoring and testing strategy.
  • Monitor growing conditions in the area.
  • Seek feedback from an agronomist.
  • Identify testing labs, both in house and externally.
  • Ensure grain is properly stored and handled.
  • Be aware of the Food Safety Modernization Act, which was passed in 2011 with implementation initiated in 2016, ensures each part of the marketing chain for feed and grains, from elevators to processors, facilitates and contributes to the production of safe food and feed and is aware of hazards in grains and feed ingredients.

Bowers emphasizes setting a plan in place before harvest and before problems arise.

“It can be hard to make management decisions when in reactionary mode,” she says. ❚

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