Horses are extremely susceptible to molds, fungi, and other sources of toxic substances in forage. Mold problems generally occur in hay that has been baled at too high a moisture level (20% or more) without the use of a preservative. This is especially a problem with first cutting hay because it is harvested during a period of time when it rains frequently and the weather conditions are less than ideal for hay drying.

Always use clean, unmoldy forages when feeding horses. In addition to molds and fungi, some forage species contain chemical compounds that can have negative health effects on horses.

* Sudangrass and sorghum-sudangrass hybrids contain compounds which can cause muscle weakness, urinary problems and death in severe cases. Do not feed these grasses to horses!

* Older varieties of tall fescue contained an endophyte fungus that could cause severe health problems if horses have only tall fescue to eat during the summer months. Mares are especially sensitive to the health problems associated with tall fescue. On pastures that contain endophyte infected tall fescue, remove mares from the pastures during the last three months of gestation. Newer tall fescue varieties that are free of the endophyte fungus are now available.

This article was graciously provided by Marvin H. Hall (mhh2@psu.edu). Please visit the web site for more information at http://www.cas.psu.edu/docs/casdept/agronomy/forage/forages.html