Studies have shown that frequent, close grazing can reduce concentrations of the harmful alkaloid in fungus-infected tall fescue. But overgrazing isn’t the best way to reduce fescue toxicity in livestock, says Mark Keaton, University of Arkansas Extension staff chair in Benton County.
He points out that overgrazing leads to inadequate dry matter availability, and also may kill any endophyte-free plants in the stand, increasing the overall infection rate. On the other hand, rotational grazing allows longer growth periods and increases alkaloid levels. Nitrogen, either from commercial fertilizer or manure, also increases forage growth and alkaloid concentrations.
“A grazing system that produces adequate forage availability and maintains a good legume content with reduced N fertilization would be more favorable than any benefits of overgrazing,” says Keaton.
Adding clover to an infected pasture will reduce but not eliminate fescue toxicity, he adds.
“Clover addition to pastures is a good management practice that reduces N fertilization need, improves animal performance and increases returns per acre regardless of endophyte status, but does not completely offset fescue toxicity.”
Similarly, fescue hay becomes less toxic in storage, but some toxin remains. In an Arkansas study, alkaloid levels over a nine-month period dropped by 79% at one location and 23% at another.
Keaton says planting endophyte-free or novel-endophyte varieties solves the toxicity problem. Both types provide good animal performance, but endophyte-free fescue isn’t recommended in Arkansas because of poor stand persistence.
Under good grazing management, novel-endophyte fescue can last as long as toxic fescue. But under poorly controlled grazing, especially during the heat of summer, stands of novel-endophyte varieties can be expected to decline. Cattle tend to graze them shorter, weakening the plants.
“Nutrient reserves are stored in the tiller bases of fescue plants, so maintaining adequate leaf area and protecting the tiller bases during summer heat stress are important for plant survival,” says Keaton.