Mold and Mycotoxins in Horse Hay
- Do not feed dusty and moldy hay and grains.
- Keep horses outside as much as possible.
- Place feed at a lower level so particles are not inhaled through the nostrils.
- Feed hay outside to minimize dust problems.
- In severe cases, hay cubes may replace hay.
- Soak dusty hay for 5 to 30 minutes before feeding. This will help minimize respiratory problems associated with dust and mold spores but will not reduce the threat of mycotoxin contamination.
- Store hay away from your horse as much as possible and ensure any hay in the vicinity is kept dry to reduce mold.
- If the horse is housed indoors, ensure that there is good, draft-free ventilation.
Table 1 contains classification of risks at various mold spore counts. While most molds do not produce mycotoxins, the presence of mold indicates the possibility of mycotoxin presence and animals being fed moldy hay should be watched carefully for mycotoxin symptoms.
Table 1. Feeding Risks* at Various Mold Spore Counts
| Mold Spore count per gram | Feeding Risk and Cautions |
|---|---|
| Under 500,000 | Relatively low Risk |
| ½ to 1 million | Relatively Safe |
| 1 to 2 million | Feed with Caution |
| 2 to 3 million | Closely observe animals and performance |
| 3 to 5 million | Dilute with other feeds |
| Over 5 million | Discontinue feeding |
*Risks refer primarily to effect of mold without regard to possible mycotoxin content. Dust may also reduce feed consumption.
Data from Richard S. Adams, Kenneth B. Kephart, Virginia A. Ishler, Lawrence J. Hutchinson, and Gregory W. Roth. 1993. Mold and mycotoxin problems in livestock feeding. The Pennsylvania State University.
What are Mycotoxins and How Can They Affect My Horse?
High moisture hay can also lead to the proliferation of bacteria, molds and fungus that can produce mycotoxins that are dangerous to horses and other livestock species. Some forage laboratories will test for the presence of mold and mycotoxins. If hay is moldy, do not feed it.
Although the effects of mycotoxins on horses are not well documented in scientific literature, in field situations apparently mycotoxin problems appear to be significant. Mycotoxins have been implicated in a variety of health problems including colic, neurological disorders, paralysis, hypersensitivity, and brain lesions. The cumulative effect of feeding low levels of mycotoxins may also contribute to a gradual deterioration of organ functions. Other symptoms of mycotoxins in forages include:
