What Mycotoxins Should We Expect Following an Interesting Growing Season? (Part 3)

The steep increase in the reported occurrence of mycotoxins including zearalenone (ZEN), type A trichothecenes (A-Trich), aflatoxins (Afla), and fumonisins (FUM) in 2023 vs. 2022 will likely catch your attention. Do these jumps in occurrence mean it’s a tremendously higher mycotoxin pressure year for these toxins? Although we’re anticipating 2023 to be a high mycotoxin pressure crop year, it’s likely that at least a portion of these shifts in occurrence are an artifact of the enhanced sensitivities of the updated Romer Labs PLUS method. The percent change in LOD values for the previous Romer Labs multi-mycotoxin method vs. the LOD values for the new Romer Labs PLUS method are reported in Table 2. The greatest change in LOD was the 98% reduction for ZEN followed by a 95% reduction in the LOD for the A-Trich. The greatest shifts in occurrence from 2022 to 2023 were also observed for ZEN (+56% points) and A-Trich (+19% points).

In contrast, there is a substantial drop in the occurrence of B-Trich with 2023 occurrence being -33% points from 2022. An occurrence of 35% of B-Trich is well below levels that have been reported for B-Trich back to 2014. The PLUS method LOD for the B-Trich increased by 5%. The author believes the change in LOD may be contributing to the shift in occurrence, but a likely greater influence could be the origin of the corn samples that have been sourced so far. We will continue to monitor the B-Trich data set closely as more samples sourced from the Upper Midwest, Great Lakes region, and Northeast are added as these regions have historically tended to be areas with higher B-Trich occurrence.

Table 2. Percent Change of Limits of Detection (LOD) for the Romer Labs LC-MS/MS Multi-Mycotoxin Methods.

In an attempt to put 2023 into comparable terms to past years, we have adjusted the values for all samples screened via the PLUS method to align with previous LOD levels. For example, a sample that had 20 ppb A-Trich detected according to the PLUS method was changed to “below LOD” (“<LOD”) for this comparison since the previous A-Trich LOD was 100.0 ppb. The adjusted results are presented in Figure 2. Again, ZEN (-79% points) and A-Trich (-22% points) experience the greatest shifts in occurrence when adjusting PLUS method results to reflect previous LOD values suggesting the jumps in occurrence for 2023 are heavily influenced by the new LOD values.

Figure 2. dsm-firmenich annual mycotoxin survey occurrence trend in 2023 US corn following adjustment of PLUS method results to align with previous LOD levels.

Although not reported this month, we anticipate the PLUS method LOD values will also influence the mean of positive results for the survey. With lower LOD, the PLUS method will be able to detect lower concentrations of most toxins on the panel. For example, the LOD for ZEN used to be 51.7 ppb and now the LOD is 1.0 ppb. Previously, a sample with 7.0 ppb of ZEN would have been reported as “<LOD”, so it would not have been considered a positive result and thus would not have been included in the mean of positives. As we see with the tremendous shift in occurrence when the LOD is adjusted lower, we anticipate seeing a higher occurrence of ZEN, but the mean concentration will potentially be lower than historical values if there are many samples positive with low concentrations of ZEN that could pull down the average.

As the survey data set continues to gain additional samples, we will continue to monitor the influence that the new lower LOD values may have on the occurrence and mean of positive contamination levels. We anticipate sharing a full mycotoxin survey update in the December edition of The Digest.

If you would like to submit samples for mycotoxin analysis to better understand risk in your feeds, contribute samples to the annual mycotoxin survey, or are curious to learn more about the analytical services dsm-firmenich offers, please contact your dsm-firmenich account manager.