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

In September, The Digest featured an article which described various factors that can increase the risk for mycotoxins in crops. The October edition of The Digest assessed the 2023 growing season and reported that many crop areas across the US experienced temperature extremes, precipitation anomalies, and other stressful weather events which have been associated with an increased risk for mycotoxins in crops. This article will share preliminary findings of the dsm-firmenich 2023 US corn mycotoxin survey and discuss how the analytical method changes at Romer Labs, Inc. that were announced in the August edition of The Digest may influence this year’s survey results.

Each year since 2004, dsm-firmenich (formerly Biomin) has conducted a global mycotoxin survey to characterize mycotoxin occurrence and contamination levels in livestock feedstuffs. Feed samples must be screened using specific analyses to determine the presence of mycotoxins. dsm-firmenich sponsors mycotoxin analyses for US customers through Romer Labs, Inc. in Union, MO. Recently Romer Labs implemented an updated liquid chromatography with tandem mass spectrometry (LC-MS/MS) method. The updated Romer Labs PLUS method has been utilized on samples that have arrived at the lab for analysis since August 1, 2023, and features enhanced sensitivities as indicated by lower limits of detection (LOD) as outlined in Table 1.
 

Table 1. Limits of Detection (LOD) and Limits of Quantitation (LOQ) for the Romer Labs LC-MS/MS Multi-Mycotoxin Methods.

*Results reported in the survey represent the summation of mycotoxin levels detected per Mycotoxin Group. For example, B-Trich occurrence and mean contamination levels are indicative of total contamination detected for DON + 3-AcDON + 15-AcDON + NIV + FusX.
**Acetyl-deoxynivalenol previously reported as a single value.

▶ Important details to keep in mind:

• A limited number of new crop corn grain samples had been analyzed as part of the survey by November 1, 2023, so only an abbreviated survey update reporting the initial data set is presented below.
• Thirty-seven samples originated from eight different states including: Iowa, Indiana, Kansas, Louisiana, Missouri, Nebraska, Pennsylvania, and Tennessee.
• Due to the limited number of samples analyzed to date as part of the annual dsm-firmenich US corn mycotoxin survey, only occurrence trends (Figure 1) are reported in this article. Contact your dsm-firmenich account manager to learn more about the initial survey data set.
• Occurrence values represent the percentage of samples which tested positive (greater than LOD) for the respective mycotoxin group  -    Example: 10 out of 37 samples had detectable levels of aflatoxins = 27% occurrence of aflatoxins in 2023 so far.
• The annual dsm-firmenich US corn mycotoxin survey includes samples submitted for surveillance testing and does not include samples submitted with reported clinical signs on-farm.

Figure 1. dsm-firmenich annual mycotoxin survey occurrence trend in 2023 US corn.

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.