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Mycotoxins: Toxic Substances from Molds That Can Harm Horses

In the global food supply for both humans and animals, molds pose a significant threat. Molds produce so-called mycotoxins—poisonous metabolic waste products. When horses ingest too many of these mycotoxins, they may develop liver problems, a weakened immune system, and digestive issues.

Digestion

Diseases

14 June '25 • 3 min reading time

Mycotoxins can proliferate due to poor storage or moist harvests of horse feed such as hay, grass, and concentrates. The toxic waste products from molds—found for example in silage—are usually invisible and odorless, but they can still negatively impact your horse’s health.

Corn, Grains, Grass

One of the most common groups of mycotoxins is fumonisins, which can be found on corn. But other molds, such as Aspergillus, can also produce toxins. Molds are especially likely to develop in corn and grains under warm and humid conditions. Mold growth can also occur in (pre-dried/silage) grass or grass-clover, producing harmful toxins. Due to climate change, mycotoxins like fumonisins are spreading—for example, because plants are being stored under warmer conditions or because pastures are stressed by drought. Austrian research confirms this rise in mycotoxin levels.

Health Risks

The health risks of mycotoxins are substantial. These waste products are harmful at the cellular level, disrupting essential bodily functions and affecting the overall health of both humans and animals. In humans, fumonisins have even been linked to cancer and neurological disorders. In horses, common symptoms include excessive salivation, liver problems, and reduced immunity due to mycotoxin exposure. In severe cases, neurological diseases may occur. Digestive issues are also frequent. Moreover, general immunity is compromised by these toxins, making horses more susceptible to other diseases. The poisoning is usually not acute but the result of chronic, long-term exposure to excessive mycotoxins. Treatment can be challenging.

Essential Oils and Herbs

To prevent mold contamination in food and feed, pesticides are often used. Due to the negative side effects of these chemicals, much research is being done on plant-based alternatives. Studies show that essential oils, in particular, can be a good substitute—not only to help preserve grains but also as supplements to combat mold and their toxic by-products inside the animal itself. Essential oils from rosemary and oregano are good examples. These plant extracts have a rich and complex composition, with powerful substances such as flavonoids and other antioxidants. They reduce the harmful effects of mycotoxins. Cinnamon, for instance, has been proven in laboratories to be effective against Fusarium molds. A supplement containing these herbs can therefore support your horse in fighting mycotoxins. Adding beneficial molds and yeasts to feed can also help strengthen the gut flora.

Bronnen:

Anumudu CK, Ekwueme CT, Uhegwu CC, et al. A Review of the Mycotoxin Family of Fumonisins, Their Biosynthesis, Metabolism, Methods of Detection and Effects on Humans and Animals. International Journal of Molecular Sciences. 2024 Dec;26(1):184. DOI: 10.3390/ijms26010184. https://europepmc.org/article/MED/39796041

Böswald LF, Gottschalk C, Kaltner F, et al. Feed-induced hypersalivation in horses from Austria, Germany and Switzerland. Equine Veterinary Journal. 2024 Nov. DOI: 10.1111/evj.14433. https://europepmc.org/article/MED/39548687

Hof H, Schrecker J. Fusarium spp.: infections and intoxications. GMS Infectious Diseases. 2024 ;12:Doc04. DOI: 10.3205/id000089. https://europepmc.org/article/MED/39386384

Son V, Penagos-Tabares F, Hollmann M, et al. Changes in the nutrient profile and the load of mycotoxins, phytoestrogens, and pesticides in horse pastures during spring and summer in Austria Journal of Equine Veterinary Science. 2023. https://europepmc.org/article/AGR/IND608695878

Zhang X, Chen J, Ma X, et al. Mycotoxins in Feed: Hazards, Toxicology, and Plant Extract-Based Remedies. Metabolites. 2025 Mar;15(4):219. DOI: 10.3390/metabo15040219. PMID: 40278348; PMCID: PMC12029259. https://europepmc.org/article/MED/40278348

Martinko K, Mioč E. Antifungal Effect of Cinnamon Bark Extract on the Phytopathogenic Fungus Fusarium sporotrichioides. Food Technology and Biotechnology. 2024 Dec;62(4):458-464. DOI: 10.17113/ftb.62.04.24.8448. https://europepmc.org/article/MED/39830871

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