For the 2017 corn harvest, a total of 442 samples sourced from 29 states were analyzed in 3 different labs (Romer Labs Inc., USA; Veterinary Diagnostic Laboratory at Iowa State University, USA; Activation Laboratories, Canada) to characterize the presence and potential risk posed to livestock animal production by six major mycotoxin groups: aflatoxins (Afla), zearalenone (ZEN), Type B Trichothecenes (B-Trich), fumonisins (FUM), Type A trichothecenes (A-Trich), and ochratoxin A (OTA). Samples included corn (293, 66%), corn silage and fresh corn chop (114, 26%), and corn byproducts (33, 7%).
A total of 88% of samples tested positive for mycotoxins compared to 96% in 2016. Type B trichothecenes such as deoxynivalenol continue to pose a major threat to livestock this year, with an occurrence at 75%, average contamination level of 1,026 ± 179 ppb (all values are presented as an average ± SEM), and maximum of 54,149 ppb. Both occurrence and average level are decreased for B-Trich compared to 2016 (85% occurrence with an average of 1682 ± 96 ppb, maximum of 30,440). FUM for the current sample pool is less than 2016 with a prevalence of 43%, an average contamination level of 2298 ± 397 ppb, and a maximum of 64,500 ppb. This is compared to 70% and an average of 3878 ± 410 ppb in 2016. However, the current sample pool is skewed towards Midwestern corn, and those in Southern areas should be mindful of FUM contamination of the 2017 crop from corn grown in these regions.
Table 1. Summary of mycotoxin analysis
|Positive samples (%)||75||43||29||4||<1||<1|
|Mean of positives [ppb]||1026||2298||248||12||135||600|
|SEM1 of positives [ppb]||179||397||55||4||15||*NA|
|Maximum contamination [ppb]||54,149||64,500||5,556||67||150||600|
1Standard error of mean
Figure 1. Prevalence (%) and average contamination level (ppb) of positive samples for Afla, ZEN, B Trich, and FUM from 2012 to 2017. OTA and A Trich are not represented due to low number of samples
The prevalence of ZEN in the 2017 harvest was 29%, with an average of 248 ± 55 ppb, and maximum of 5556 ppb. Average sample contamination level and prevalence is lower for ZEN compared to 2016 (2016: prevalence at 56% with a mean of 339 ± 62 ppb). Prevalence and average contamination levels of B-Trich, FUM and ZEN are less than 2017, and appear similar to 2015. Contamination levels of B-Trich and FUM remain above 2015 levels. The overall trend has been increasing prevalence of B-Trich and ZEN contamination since 2013, with a decreasing trend of FUM. Afla prevalence in the sample pool appears to have decreased since 2012, but this year due to weather during the harvest and out-door storage of bumper crop corn, producers should remain vigilant of corn quality and storage conditions throughout the calendar year.
Figure 2. Threat of mycotoxin-related risks to livestock based upon threshold levels according to FDA and EU regulatory and guidance values. States from which samples with levels of contamination representing a high risk are illustrated in red. States with positive samples below high threshold levels are illustrated in pink, without positive samples are illustrated in dark grey, and without samples submitted are illustrated in light grey. State information was not available for all samples. The maximum level does not preclude specific, severe instances of mycotoxin contamination in farm or fields locally, nor does it account for the negative impacts of multiple mycotoxin presence. OTA and A-Trich maps are not included due to small number of positive sample
The contamination of samples with B-Trich above 900 ppb and FUM above 2000 ppb was observed in 12 and 17 states, respectively. Zearalenone levels exceeding 100 ppb were detected in samples from 16 states. The occurrence of samples above threshold levels for Afla, T-2 and OTA were sparse, and found in samples from single sources. The occurrence of Afla above 20 ppb was detected in South Carolina, A-Trich at levels above 100 ppb did not have state information, and OTA above 100 ppb was found in Ohio.
Figure 3. Distribution of contaminated samples
Detected occurrence above the risk level of 100 ppb was 59% for ZEN (73% in 2016) while it was 26% for B-Trich above 900 ppb (51% in 2016), and 28% for FUM above 2,000 ppb (42% in 2016). This 2017 harvest, B-Trich, ZEN, and FUM present the main threats in the US corn, consistent with previous years.
With more than ten-years of experience monitoring the occurrence of mycotoxins in livestock feeds, BIOMIN has shown that co-occurrence of mycotoxins (the presence of more than one mycotoxin) is the rule and not the exception. As illustrated in Figure 4, 43% of US corn samples harvested in 2017 were contaminated with just one mycotoxin while 45% showed co-contamination with more than one mycotoxin, a decrease from 2016 and similar to 2015. Of the co-contaminated samples, 15% were positive for all three fusarium toxins (B-Trich, FUM, and ZEN), while co-contamination with B-Trich and FUM, and B-Trich and ZEN were 16% and 13%, respectively.
Figure 4. Co-occurrence of mycotoxins from 2012-2017.
Overall, B-Trich such as deoxynivalenol present the highest threat in the US corn harvest samples due to its high prevalence and number of samples above the FDA recommended level.
In terms of occurrence, FUM ranks second among the six major mycotoxins analyzed in these samples. As a result of its co-occurrence with other toxins, ZEN continues to be a concern in US corn.
While occurrence and co-occurrence levels in 2017 have decreased compared to 2016, data suggests fusarium toxins in combination remain a threat to the livestock industry.