According to the dsm-firmenich World Mycotoxin Survey, which assessed the global mycotoxin threat, 86% of North American samples tested above the recommended threshold for at least one mycotoxin. While mycotoxin levels haven’t necessarily escalated from 2024 to 2025, there was a shift in the distribution, which has some implications for cattle and swine operations.
“The 2025 results show a continued mycotoxin challenge, with contamination rates rising for both aflatoxins and zearalenone and average levels increasing across all major mycotoxins,” said Ursula Hofstetter, head of mycotoxin risk management at dsm-firmenich, in a press release.
The Major Players
Mycotoxins are toxic metabolites produced by fungi, most commonly Fusarium, Aspergillus and Claviceps species. They develop in the field and can persist through harvest and storage. Weather stress, hybrid selection and storage management all influence which toxins dominate in a given year.
The primary mycotoxins shaping North American livestock risk in 2025 were:
- Deoxynivalenol (DON)
A Type B trichothecene produced by Fusarium species. Commonly found in corn and wheat. Often referred to as ‘vomitoxin’. - Zearalenone (ZEN)
Also a Fusarium toxin. Structurally estrogenic and frequently present alongside DON in corn and small grains. - Fumonisins (FUM)
Produced by Fusarium verticillioides and related species. Predominantly found in corn. - Aflatoxins (AFLA)
Produced by Aspergillus species. More common in drought- or heat-stressed corn. - Ergot alkaloids (ERGOT)
Produced by Claviceps species. Typically associated with small grains.
These toxins rarely occur in isolation. Co-contamination often shapes the reality producers see on the farm.
What Changed from 2024 to 2025
The 2025 North American mycotoxin prevalence in raw materials compared to 2024 shows the following shifts:
- DON: 74% → 76%
- ZEN: 73% → 78%
- FUM: 46% → 55%
- AFLA: 15% → 17%
- ERGOT: 44% → 9%
Trichothecenes remain deeply entrenched, with DON prevalence increasing slightly. Most of this increase is a result of an increase in wheat (73% → 93%). Meanwhile, fumonisins rose meaningfully and ergots dropped sharply.
Cattle: Rumen Function, Immune Resilience and Production Losses
Cattle historically are considered somewhat more resilient to mycotoxins than monogastrics, owing to partial ruminal detoxification. However, evidence increasingly shows persistent exposure to Fusarium toxins like DON, ZEN and FUM, especially in combination, can exert significant effects on digestion, immunity and metabolic health.
When looking at global finished feed samples for ruminants:
- DON was prevalent in 69% of samples and above the risk threshold in 53% of samples.
- ZEN was prevalent in 73% of samples and above the risk threshold in 33% of samples.
- AFLA was present in 34% of samples and above the risk threshold in 29% of samples.
Studies have demonstrated short-term exposure to Fusarium toxins, including ZEN and FUM, affects fermentation patterns and the microbial community, which in turn can reduce fiber breakdown and volatile fatty acid production — key drivers of energy supply in cattle. Even modest disruptions to the rumen microbiota can reduce feed efficiency and gain over time.
The immune system is also affected by mycotoxins. The immunosuppressive effects of common mycotoxins in ruminants have been documented, including alterations in cytokine gene expression, immunoglobulin production and macrophage function.
Further, individual toxins like AFLA have well-established effects on liver function and general metabolism in cattle. Chronic AFLA exposure has been linked to reduced appetite, lower weight gains and elevated liver enzymes, indicating compromised hepatic function that can impact production and health resilience.
These findings indicate how cattle performance and disease resistance can be eroded by the mycotoxin patterns reported in the 2025 data. Persistent DON and ZEN exposure, combined with higher FUM presence, places additional load on rumen fermentation and immune competence, potentially contributing to subclinical production drift.
Swine: Immune Disruption, Gut Barrier Injury and Performance Drag
In swine, elevated prevalence of DON, ZEN and FUM can exert systemic effects on immune function, gut integrity and reproductive physiology at both clinical and subclinical levels.
When looking at global finished feed samples for swine:
- DON was present in 85% of samples and above the risk threshold in 41% of samples.
- ZEN was present in 79% of samples and above the risk threshold in 19% of samples.
- FUM was present in 44% of samples and above the risk threshold in 8% of samples.
Research has shown DON and FUM alter the gut epithelial barrier, impair immune defenses and increase bacterial translocation from the gut, making pigs more susceptible to infections even when properly vaccinated. In the immune tissues themselves, DON exposure has been linked to changes in the gene expression of key antimicrobial and inflammatory regulators, implying a weakened ability to respond to disease challenge at the cellular level.
ZEN adds another layer of complexity. Beyond its well-known estrogenic effects (i.e., swelling of reproductive tissues and altered estrous cycles), ZEN has been shown to suppress antibody production in porcine immune cells, reducing levels of IgM, IgG and IgA. These immunoglobulins are important for protective vaccine responses. This explains why farms employing what should be effective vaccination programs still report breakthrough disease.
Collectively, these mechanisms mean widespread DON and ZEN exposure is a disease vulnerability issue. When the gut barrier is compromised and immune cell function is suppressed, pigs are less able to defend against respiratory pathogens, enteric bacteria and systemic infections alike, and their response to vaccination may be diminished.
Mycotoxin Co-Contamination Defines 2025
The defining feature of mycotoxins in 2025 is not a single toxin spike, but co-contamination. Feeds routinely contain multiple mycotoxins at once and their effects overlap, creating steady biological pressure.
The result is rarely dramatic toxicosis, but production drift is reflected in reduced gains, narrower reproductive margins, lowered health resilience and increased performance variability.
With persistent DON, rising ZEN and higher FUM prevalence in North America, ingredient-level vigilance and close monitoring of performance trends are important. The mycotoxin burden did not spike, but it did rearrange.
