Challenges of Fescue
Even though tall fescue is widely dispersed in the US, 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 with the endophyte. The fungus is not transmitted plant to plant, 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.
Issues of Infected Fescue for Livestock
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.
Three major types of animal disorders associated with consuming endophyte infected fescue forage or seed are fescue foot, bovine fat necrosis, and fescue toxicosis.
- Fescue foot is characterized by gangrenous and necrotic tissue at the animal’s extremities, namely the tail, ears, and feet, with severe cases showing loss of the tail or hoof. This disorder usually occurs during the winter, especially when grazing stockpiled or N-fertilized tall fescue.
- Fat necrosis is the accumulation of dense, necrotic fat deposits in the abdominal cavity of cattle, and occurs most likely in virtually pure tall fescue stands amended with high rates of N fertilizer. Acute cases can cause death in cattle by intestinal strangulation. Evidence suggests that fat necrosis is associated with consumption of endophyte-infected fescue; however, direct cause and effect have not been established.
- Fescue toxicosis describes the general conditions of unthrifty appearance and poor animal performance, exhibited especially during high temperature periods. This disorder is responsible for the major economic losses to the USA beef industry caused by consumption of endophyte-infected tall fescue. The complex of symptoms includes poor weight gain and milk production, rough hair coat, excess salivation, elevated body temperature, depressed serum prolactin levels and standing in shade and water. Milk production on endophyte-infected grass may be reduced by up to 50 percent.
It is important to realize that while you can manage grass to have higher protein or higher energy, if you do not deal with managing around the alkaloid toxins produced by fescue, you still will not have good animal performance. Many data sets show that cattle on endophyte infected tall fescue will gain 30-50% less than cattle grazing the same varieties of endophyte free or novel-endophyte fescues. Beef cow studies often show a 20-30% reduction in pregnancy rates with average management on high endophyte pastures.
Thus, you need to manage not only for yield and forage quality, but also the toxin levels. Taking this into consideration, your management decisions on when and how to use fescue may change. Intake of fescue alkaloid levels are highest when fescue is rapidly growing – especially late May and June when fescue grows a stem and seed heads. Alkaloids also can be high during early fall pasture growth. If possible, it may pay to rotate the cattle to other forage sources when fescue matures in the spring and when you get a flush of fall growth. Use the fescue heavily in early spring, try to keep seed heads and stems from emerging, and use the fall growth as a stockpiled feed for winter grazing.
If you do not want to replace the fescue pasture, manage what is there by adding practices that dilute or reduces the amount of alkaloid consumed, including rotating to other pastures or hay fields, frost seeding legumes to the pasture, supplementing the cattle with grain or grain co-products, ammoniating fescue hay, clipping pastures, and using stockpiled fescue in the winter. You also should be careful in adding nitrogen fertilizer to fescue pastures – nitrogen addition will increase the concentration of alkaloids.
Tall fescue is here to stay. Implementing practices that reduce the amount of alkaloid ingested will reduce fescue-caused disorders and improve your herds overall productivity.
This article also appeared in Mid-America Farmer Grower, July 8, 2021.