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What we learned from 2020 mycotoxins

John Winchell for Progressive Dairy Published on 17 March 2021

As we entered a new year, with high commodity prices and a recent longer cold stretch, we have begun to see some cow issues. This is not all too uncommon from January to April, as we usually see cowside issues arise.

The following observations are what I have been seeing working with many farms, consultants and companies throughout the Northeast:



  1. New-crop corn silage is a tale of two cities.
  2. Digestive upsets are beginning to show up on some farms in the last month.
  3. The mycotoxin signature is similar to other years, yet a little different than normal.
  4. Straw is problematic again this year.
  5. Weather really impacted this season’s crop in many ways.

A review of 2020 weather

Below is a chart that shows the 100-year high in growing degree days in the northeast from May to October. Climate smart farming (CSF) can be used with multiple planting and harvest dates by individual farm address. CSF also tracks growing degree data for this season: a 15-year average (blue) and 30-year normal (purple) for comparison. You can also look at the frost dates over the last few years. You can see the green line (2020 actual) is overlapping the black line, which indicates the 100-year high in temperature.

Growing degree day image

Corn silage review

We will focus on corn silage, as it is the largest grown crop in the Northeast. 2020 corn silage harvest was interesting. With great growing degree days and some timely post-tassel rains, we saw ears drying down quicker than stalks and ears that popped out of husks in many situations. Harvest was earlier for most farms, but a killing frost that hit in September made harvest tricky. Farms that harvested prior to this frost, or were in the middle of chopping when the frost hit, did not experience too many issues with mycotoxins. It was farms waiting for whole plant dry matter (DM) to decrease, or herds that had a lot of acres to cover, that got caught with rapid dry downs and 40-plus DM corn silage. These are the farms that should consider checking for mycotoxins. As you can see in the two examples below, there is a need to review those drier corn silages.

Figures 1 and 2 show a silage on continuous corn. Corn that had a great growing season went from a little less than 30% DM to 45% DM in 12 days. This was assisted by frost and then higher than normal temperatures, some rain, wind and droughty conditions that many of us faced from the middle of August to the middle of September. This corn was on the edge, and the frost pushed it over the edge. There was a 17-times increase in deoxynivalenol (DON) levels in 12 days, to the tune of 4-plus parts per million (ppm) DON. The conditions were just perfect for late-season DON, post frost.

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Tables 1 and 2 show corn of the same variety that was planted on the same date and harvested on the same date. Table 1 consisted of 37% DM, while Table 2 consisted of 48% DM. The difference is soil type. The sample on the left was on heavier ground that saw a little more rain, the other was on gravel ground that was droughted. This stressed corn was very sensitive to rapid dry down and also higher DON levels, to the tune of 7-plus ppm.

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What does this mean for the corn silage mycotoxin average for 2020? It sits a little less than average for DON in the Northeast for the last few years. We still are sitting at 2 ppm of DON, but there are many low numbers and some big numbers out there. I am starting to see more issues from a T-2 toxin, penicillium and DON combination. For those that I work with, know this is a bad combination for high cows, fresh cows and pre-fresh cows. Mix in recent cold stress, frozen feed and drier corn silage with normal stress issues on the farm, and you could see some issues.

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Haylage and straw

Don’t dismiss haylage, which is normally not a real high risk for mycotoxins. The first cutting this season can be problematic due to the March to June 1 period that exhibited a cooler and cloudier spring. More penicillium issues have arisen in the first cutting due to slower fermentation and often times a little wetter first cutting, which we know will delay fermentation. Penicilliums were higher risk in 2017, when we had a similar spring. Other cuttings have been very low risk, like normal.

Also, make sure to test your straw. I have been seeing a lot of issues that go beyond a simple mycotoxin panel. Storage mycotoxins coming from penicillium and aspergillus mold species are a result of “wetting” in the straw harvest. So, if you are having some pesky transition issues, the straw might be worth a mycotoxin test.

Key takeaways

So, what does this all mean? We need to test our corn silage and total mixed rations (TMRs) for mycotoxins, to see what the risk levels are. Overall, risk levels are not very high, but consideration of all possibilities is key to proper diagnosis and remedy of an issue. If you have been seeing indigestion, fluctuating intakes and more immunity issues since getting into a drier corn silage, you should test. Also, with commodity prices increasing, and forage on the tight side, we are seeing an increase in byproducts being fed. This can increase mycotoxin risks from those corn by-products, which traditionally show higher risk. One last note, we are also seeing aflatoxin in cornmeal in pockets that were droughty and hot. This is very uncommon for the Northeast, but it warrants some attention.

A lot of time has been spent testing feeds, walking fields and barns, and analyzing weather trends.  It is fascinating to study mycotoxins the last few years to learn the nuances and ways to control the risks of mycotoxins on Northeastern farms. The Northeast is mycotoxin central, and managing mycotoxin risk involves a whole-season program that can be very beneficial for our farms and cows. We are all in this together.  end mark

John Winchell
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