Tall fescue is widely grown throughout Missouri, in part due to its ease of establishment, wide adaptation, long grazing season, tolerance to environmental stress, and pest resistance. However, it is often infected with a fungal endophyte which can have detrimental effects on herd performance. Surveys in several states indicate that most tall fescue pastures are infected 60 to 80 or more percent with the endophyte. A recent study by MU indicated that producers may not be managing the endophyte in the most efficient way, and in winter should feed hay first, then stockpiled fescue.

The fungus ("endophye" is a Latin translation, indicating that the fungus lives within the plant) is not transmitted plant to plant in a field, but rather is seed transmitted. As the seed germinates, the fungus moves within the space between the plant cells into developing shoots. During vegetative growth, the fungus grows into the leaf sheath only, and does not grow into the blade. Toxins produced in the sheath, however, are translocated to the blade. Later, the fungus grows up into the developing seed. When that seed germinates, it is infected as well. Cattle (and sheep and horses) feeding on infected fescue may exhibit one of several toxicosis syndromes, including reproduction problems, low calf weaning weights, and poor gains. Milk production on endophyte-infected grass may be reduced by up to 50 percent.

Livestock problems on infected fescue result from an ergot-like alkaloid, ergovaline, which is produced by the fungal endophyte. Ergovaline is present in hay and seed of endophyte-infected fescue, and feeding can result in poor animal performance.

Results from a two-year study at MU Southwest Research Center shows that the current practice of managing fescue problems in stockpiled hay may not be the best. Waiting longer to feed stockpiled fescue results in a lower ergovaline content, while still maintaining the fescue’s nutrient value. Typically, pasture to be stockpiled for winter is grazed through August, fertilized, and allowed to regrow until a killing frost. The pasture is then grazed. Research shows that waiting later in the winter to feed the stockpiled fescue leads to a lower ergovaline content.

In winter 2000, the MU study found ergovaline content in mid-March was less than 20% of what it had been in mid-December. Previous studies indicate that an ergovaline content above 150 ppb (parts per billion) can lead to problems. In this study, ergovaline content dropped below that critical level by the end of January. In its second year, results of the study were similar to those of the first. The study also supposed that differences in ergovaline content are related to weather, with

lower levels of the toxin showing up in years with cool, wet fall weather.

Crude protein (CP) values for the stockpiled fescue increased slightly from mid-December to mid-March, while ADF (acid detergent fiber) and NDF (neutral detergent fiber) remained equivalent over the same time period.

For more information on tall fescue and its endophyte, request a copy of the free publication, G4669: Tall Fescue Toxicosis, from your local UOE Center.