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ES Insulin dysregulation in horses: a new epidemic or a new perspective?
September 9, 2024
Mycotoxins, microbial contamination, and what you as an owner really need to know
Every horse owner knows that good nutrition forms the basis of health, performance, and well-being. But even when the ration looks perfect on paper, something can lurk that isn't immediately obvious: invisible threats such as mycotoxins and microbial contamination. These factors can undermine the immune system, cause digestive problems, and even contribute to laminitis or colic. Time to delve deeper into this complex but crucial topic.
Mycotoxins are toxic metabolites produced by certain fungi, particularly from the genera Aspergillus, Fusarium and Penicillium. These fungi thrive in warm, humid conditions — precisely the conditions in which poorly stored hay, grains, or by-products can easily end up.
Hundreds of mycotoxin types are known, but the most relevant for horses include:
Aflatoxinshepatotoxic, immunosuppressive
Zearalenonehormonal imbalance, especially in mares
DON (vomitoxin)decreased appetite, bowel disorders
Fumonisinspotentially neurotoxic and harmful to the lungs
Even in low concentrations, mycotoxins can have a cumulative and insidious effect, especially in horses with a sensitive digestive system or a disturbed intestinal flora.
Besides fungi, bacteria such as Clostridium botulinum and Salmonella spp. develop in poorly stored feed. This increases the risk of serious disorders such as:
Botulismparalysis, muscle weakness, potentially fatal
Salmonellosisdiarrhea, sepsis
Colitiscolitis resulting in colic, dehydration, and fever
endotoxemialife-threatening systemic reaction to bacterial toxins
Also, mold spores and dust particles from moldy hay can cause respiratory problems, such as chronic coughing or asthma. Respiratory issues in horses are therefore not only caused by a dusty stable.
A contaminated ration does not always have to lead to acute symptoms. On the contrary: much of the damage happens slowly, invisibly, and cumulatively. Possible signs are:
Decreased appetite or selective eating
Unexplained weight loss
Behavioral changes or increased irritability
Recurrent colic or diarrhea
Dull coat or reduced hoof quality
Reduced performance or recovery capacity
Keep hay dry, ventilated, and off the ground (use pallets).
Leave space between bales for air circulation.
Check for a musty odor, discoloration, or mold growth.
Protect pre-dried hay from light and air — only open just before use.
Use pre-wilted silage within a few days of opening.
Store in clean, airtight containers of plastic or metal.
Store them in a cool, dry, and dark place.
Use the FIFO principle: what comes in first must also be recorded first.
Only buy quantities that will be used up within 4 to 6 weeks.
Clean food and water bowls daily.
Check daily for spoilage, moisture spots, or pests.
Use natural moisture absorbers if necessary (such as salt packets).
Pelleted feed is produced under high temperature and pressure, which reduces the microbial load. However, this does not mean that it is better by definition. Not every horse likes pellets and some ingredients are more sensitive to heating. Moreover: clean feed starts with clean raw materials and a correctly stored final product — regardless of the form.
Rolled oats are more easily digestible, but have a shorter shelf life and are more susceptible to microbial growth. Whole oats are more stable, richer in antioxidants and fiber, and have a lower glycemic index. The choice depends on your horse's individual digestion and sensitivities.