Mould and mycotoxins

Mould toxins in forage are invisible, odourless and slip past a standard analysis — and the horse is especially sensitive to them. A few insights.

A clean forage analysis tells you nothing about mould toxins

Standard forage analysis (NIR) measures bulk nutrients like energy, protein and sugar — it cannot see mycotoxins, which act at microgram levels and are invisible to the eye and nose as well. A sweet-smelling, good-looking, 'passed' batch of hay can still be contaminated. The only test that detects them is a specialised laboratory method (LC-MS/MS).

Of all farm animals, the horse is the most sensitive to one maize mould toxin

A mould toxin called fumonisin, found on maize and maize by-products, causes a fatal brain disease in horses. Pigs and poultry are far more tolerant, so 'it's fine for other livestock' does not apply — the horse is the sensitive species. A horse on maize showing sudden neurological signs is a veterinary emergency.

EU mould-toxin limits are not a horse safety line

European guidance values for mould toxins were set for the most tolerant species and are explicitly described as upper limits, with lower values meant to apply to more sensitive animals. Horses are a sensitive species — so feed that merely 'meets EU guidance' is not proven safe for horses; those figures are a ceiling to sit well below.

One sample can miss mould toxins — testing must be composite

Mycotoxin contamination sits in patchy 'hot spots', so a single grab sample often gives a false all-clear. Valid testing means taking many sub-samples from across a batch, combining them, and submitting that mixed sample to the laboratory.

This is general information. It does not replace the individual feeding plan your EVN vet prepares for your horse after assessing it.