The 2017 growing season was challenging across the U.S. Growers in different regions experienced varied weather conditions that could not only reduce yield, but could also increase plant stress and lead to challenges with mycotoxins.
Corn silage samples from across the entirety of the U.S. have shown extremely high levels of mycotoxins, particularly deoxynivalenol (DON), type A trichothecenes (T-2), fusaric acid and fumonisin.
Mycotoxins are a regular concern for producers, as they influence feed quality and animal safety. Although mycotoxins were first identified over 50 years ago, they are gaining more attention due to changing agricultural practices, improved analytical technology, new scientific research and varying climate conditions.
They are seldom found in isolation, and when multiple mycotoxins are consumed, they may have additive, or even synergistic, interactions that increase the overall risk to performance and health.
Mycotoxin risks
As the name implies, mycotoxins are toxic. They can negatively affect animal health if contaminated feedstuffs are ingested. The symptoms can be many and varied, but the outcome in all cases will be reduced performance and lost profits.
Produced by certain molds, more than 500 mycotoxins have been discovered to date. Each affects the animal or human in a certain way. Some mycotoxins are carcinogenic, neurotoxic and immunosuppressive.
Climate change and feed storage practices are starting to influence the range of molds occurring in farm feedstocks. And with traditional tilling and crop rotation practices diminishing in many developed countries, mold contamination is persisting year-on-year, making the multiple mycotoxin threat very real.
It is important to note that once there are mycotoxins in the crop, they will not go away. There will be higher levels of mycotoxins on farms practicing monocropping of corn, as opposed to those farms rotating crops or using deeper tillage methods.
Harvest analysis
Samples submitted to our mycotoxin analytical services laboratory between Sept. 1 and Nov. 30, 2017, show that grains contained mixtures of mycotoxins, including DON, fusaric acid and fumonisin. Forages such as corn silage, barlage and haylage samples also contained multiple mycotoxins in 2017, including DON, fusaric acid, T-2 and fumonisin.
Mycotoxin levels in corn silage are averaging higher than the same time period the prior year. Type B trichothecenes (DON group) show an increase from the 2016 average of 983 parts per billion (ppb) (max 12,876 ppb) to a 2017 average of 2,564 ppb (max 17,437). In the case of fumonisins, the 2016 average was 803 ppb (max 18,193 ppb), increasing in 2017 with an average of 2,068 ppb (max 53,046).
T-2/HT-2 toxins increased from the 2016 average of 6.8 ppb (max 650 ppb) to the 2017 average of 164 ppb (max 3,712) (Figure 1).
For dairy cows, the analysis shows a higher risk level occurrence of mycotoxin levels in corn silage of type B trichothecenes, with 37.7 percent of corn silage samples above 2,000 ppb (2 parts per million [ppm]) and a moderate risk level for 54.6 percent of corn silage samples above 1,000 ppb (1 ppm).
In terms of T-2/HT-2 toxins, 14.5 percent of corn silage samples were above 100 ppb, which is a moderate risk level for dairy cows.
Fumonisin is trending higher across all states and can have a negative impact on feed intake, gut health, liver function and immune response. It is commonly found in corn at levels of 2 ppm or less, but this year, testing has confirmed levels well above 30 ppm, and some above 100 ppm.
For example, the Wisconsin-Minnesota area results show seven-tenths of a mycotoxin-per-sample higher than a year ago. More of the samples submitted contain mycotoxins, and the major toxins present are four to five times higher than they were a year ago.
Effects of mycotoxins
When cows consume feed contaminated with mycotoxins, there can be negative effects that result in long-term declines in performance and, ultimately, lower farm profitability. Chronic mycotoxin consumption, where smaller quantities of contaminated feed are consumed over time, is often more challenging than an acute single dose, as the mycotoxin risk may not be noticed until a loss of production and health has already occurred.
Although the rumen microorganisms can help degrade some mycotoxins, they may also convert other mycotoxins into more potent forms.
Certain mycotoxins can pass through the rumen unchanged to be later absorbed in the small intestine, while other mycotoxins may have antibiotic-like effects directly on the beneficial rumen microorganisms. As a result, the rumen and gastrointestinal tract are main targets of mycotoxins in cows.
Based on the fusarium mycotoxins (DON, zearalenone [ZEN], fusaric acid and T-2/HT-2 toxins) detected in this year’s grain and forage samples, cows may show a multitude of symptoms, such as changes to feeding behaviors, rumen disorders, lesions or hemorrhaging of the gastrointestinal tract, altered conception rates, lower milk production or altered milk components, and increased disease occurrence.
Dairy animals may also have poor udder health with increased somatic cell counts or increased incidence of mastitis.
Influencing mycotoxins
Mycotoxin occurrence and concentration are influenced by many factors, including drought, excess rainfall, hot or cool temperatures, pests and agronomic practices.
In 2017, many regions of the U.S. experienced a cool, wet summer, the preferred environment for fusarium mold, resulting in high levels of DON, T-2, ZEN and fusaric acid – mycotoxins that can become very problematic in corn silage (Figure 2).
Higher levels of mycotoxins appear to be a lingering legacy of the havoc Hurricane Harvey delivered to the Texas Gulf Coast in mid-August.
In Texas, samples show dramatically high levels of fumonisin. The results can be tracked northward from where the rainfall came up from the Gulf and across the Texas Panhandle into Kansas and Nebraska. The levels of fumonisin will begin to decrease, but they are still much higher than the levels those areas would typically experience.
While weather is linked to the higher mycotoxin rates of recent years, other important factors are contributing to the scope of the findings, including better detection methods as well as increased awareness among farmers.
Technology has allowed for the ability to test for mycotoxins and, with continual advancements, allows for tests to identify more toxins. Also, different agronomic practices, such as tillage practices or fungicide use, may have an influence.
Co-occurrence of mycotoxins
Mycotoxins are seldom found in isolation, and when multiple mycotoxins are consumed, they may have additive or synergistic interactions that increase the overall risk to performance and health. As a result, an animal may have a stronger response than what would be expected if only experiencing a single mycotoxin challenge.
Mycotoxins present researchers with challenging paradoxes. Feeding multiple mycotoxins at low levels can be as detrimental or worse than feeding one mycotoxin at a high level. One mold species may produce many different mycotoxins, and several species may produce the same mycotoxin.
Producers should remain aware of multiple mycotoxins and the risk they present. As more complex feeds with more ingredients are made, an increased amount and different combinations of mycotoxins are brought together in one place where the animal will have the opportunity to consume it, increasing the opportunity for risk.
On-farm management
For the feedstuffs harvested in 2017 and are currently being fed, it is important to conduct a mycotoxin analysis that identifies the storage mycotoxins, including penicillium and aspergillus mycotoxin groups, as there is added potential for additional mycotoxins to develop during storage.
Storage measures can help reduce the risk of further mold and mycotoxin development, such as:
- Properly dry grains to less than 13 percent moisture.
- Improve packing density.
- Ensure proper fermentation has occurred.
- Inspect storage quality to minimize moisture, air, insect or pest entry.
- Conduct mycotoxin analysis at harvest and after storage to identify the appropriate management strategy for those feedstuffs.
Mycotoxins are a challenge to animal and feed production, and employing preventive measures for managing mycotoxins is essential to minimize profit loss.
Proper mycotoxin management techniques can reduce the risk of mycotoxins coming from feed materials and help prevent the negative effects on performance and health. 
Alexandra Weaver also works in mycotoxin management for Alltech. Email Alexandra Weaver.
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Max Hawkins
- Mycotoxin Management
- Alltech
- Email Max Hawkins
