Kentuky-31 tall fescue, the most used grass in Missouri pastures, contain an endophyte fungus that produces toxic alkaloids. The toxic ergot alkaloids can lead to a condition called fescue toxicosis. Fescue toxicosis is a severe forage-livestock disorder costing Missouri’s beef industry $160 million each year in reduced weaning weights, conception rates, and milk production.
Many farmers wonder what happens to tall fescue toxin levels when it is baled for hay. Toxin levels decrease in hay. This is because ergot alkaloids break down in the presence of light, heat, and oxygen. About one half of the toxins disappear within six months after baling. Even though the toxin levels are reduced the forage is likely above threshold levels for fescue toxicosis and other alkaloid management strategies will need to be implemented. Full article: Roberts et al., 2009. Crop Sci. 49:1496-1502.
Producers should use caution when feeding toxic, tall fescue silage. When silage is made (oxygen is deprived) the toxins remain and are well preserved. Full article: Roberts et al., 2014. Crop Sci. 54:1887-1892.
Wet weather conditions this spring have delayed hay and silage harvest for a large portion of Missouri. The delay in harvest has resulted in tall fescue seedheads emerging in hayfields. When tall fescue is reproductive, the seedhead is one of the most toxic portions of the plant. Hay and silage containing seedheads should be considered highly toxic.
Whether tall fescue is manage for pasture, hay, or silage there are some strategies that should be implemented to minimize the impact to livestock. Producers should strive to manage tall fescue to minimize toxicity by incremental alleviation, which is the additive effect of several management practices. Incremental alleviation includes interseeding legumes and other forages, rotating livestock to warm season grass paddocks, nitrogen management, and grazing height management.
Incremental alleviation does not directly address the production of toxic alkaloids in tall fescue. Replacing tall fescue with novel endophyte fescue is the only way to completely eliminate the costly effects of fescue toxicosis. Fields converted to novel endophyte tall fescue should follow the spray-smother-spray protocol prior to establishment. Novel endophyte tall fescue cultivars will have the Alliance for Grassland Renewal label which verifies that it meets novel specification.
Contact Sarah Kenyon, Field Specialist in Agronomy, for more information KenyonS@missouri.edu or 417-256-2391. Also, the guide sheet Tall Fescue Toxicosis can give more information on this complex issue: https://extension2.missouri.edu/g4669