Storage Method Affects the Ergovaline Concentration of Tall Fescue

Tall fescue covers over 12 million acres of pastureland in Missouri. It accounts for more acres than corn, soybean, and wheat combined, and is therefore one of Missouri’s most important crops. The biggest drawback to the use of tall fescue as pasture is the toxicity associated with a microscopic fungus known as the endophyte. The fungus produces poisonous alkaloids, such as ergovaline. These poisonous alkaloids ultimately reduce feed intake and therefore live weight gains in feeder cattle and complicate breeding and milk production in cows. In the last few years, our knowledge of the ecology of tall fescue has expanded greatly and allowed for better management of the grass. Still, questions remain concerning the toxicity of tall fescue. Our objective for this experiment was measure the amount of ergovaline conserved in tall fescue when different storage methods to harvest the forage.

Materials and Methods

A plot of 80% endophyte infected tall fescue was fertilized with 75 lb/acre of nitrogen in early March. On May 20th, tall fescue was cut with a disc mower and fresh forage was immediately put in bags and stored in a freezer. The remaining forage was allowed to cure in the field and baled at 20% moisture. Half of the baled hay was then sealed in 6 mil black plastic and anhydrous ammonia was applied at the target rate of 3 lbs. ammonia for each 100 lbs. of dry hay. The ammoniated hay was kept sealed for 42 days and then both types of hay were sampled. Total alkaloids were measured from each storage method.

Results and Discussion

Averaged across two years, the ergovaline in growing tall fescue was 336 parts per billion. This level was nearly 50% greater than the other storage methods. Hay and ammoniated hay all had equal amounts of ergovaline when sampled. Other studies support this finding, showing that hay and ammoniated hay have the least amount of ergovaline or ergot alkaloids.

Conclusions

Making hay and treating it with ammonia is one way to reduce the amount of ergovaline in tall fescue fed to cattle, although haymaking is often at the mercy of the weather. These data imply that haymaking could be deferred until late spring. Though it would be toxic, it could be ammoniated to detoxify it. Additionally, the data imply that the straw aftermath that is left after a seed crop is harvested could be ammoniated. This information adds to the base of knowledge we are compiling to manage tall fescue.

Table 1. The concentration of ergovaline in Tall fescue harvested in late May and stored by different methods.

This material is based upon work supported by the U.S. Department of Agriculture, under Agreement No. 58-6227-3-016.

Any opinions, findings, conclusion, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture.