Understanding Symptoms Prevention and Pasture Management Strategies
Livestock producers are reporting more concerns about fescue toxicosis, a condition linked to toxic tall fescue consumed by grazing animals. While common in southern regions, recent years suggest the problem is appearing farther north or is being recognized more consistently.
The condition is most familiar in horses due to significant reproductive issues, but cattle and small ruminants have also shown negative performance impacts.
Fescue toxicosis refers to harmful effects caused by ergovaline, a toxin produced by an endophyte, a fungus that grows inside tall fescue plants.
Although it benefits the plant by improving drought tolerance, disease resistance and insect protection, the toxin can negatively affect livestock.
Because ergovaline restricts blood flow, animals may develop lameness, rough hair coats, high body temperatures, poor milk production, reduced weight gain and, in severe cases, loss of hooves or tails. Producers should consult a veterinarian because several illnesses can appear similar.
Toxin levels are typically highest in late spring and summer when seedheads develop. These seedheads contain the greatest concentration of ergovaline.
Later in the year, toxin levels shift toward the lower parts of the plant. Overgrazing during this period increases animal exposure.
Recent drought conditions have added to the challenge. With pastures under stress, tall fescue has often outlasted more desirable grasses.
As grasses thin, weeds and stressed forage species fill open spaces, reducing the dilution of toxins. This situation may explain increased reports of toxicosis during fall grazing in recent years.
Producers can reduce risks through several strategies. One of the simplest is pasture diversification. Adding red or white clover or other forage species helps dilute toxin intake.
Frost seeding clover is a common and successful practice. Establishing additional grass species through a no‑till drill also lowers the overall concentration of infected tall fescue.
For severe pasture infestations, complete renovation may be necessary. Some tall fescue varieties lack toxin‑producing endophytes or contain novel endophytes that protect the plant without harming livestock. However, eliminating infected seed requires a multi‑step process.
Stored hay and stockpiled forage naturally lose toxins over time, offering safer feeding options. Producers can also submit pasture samples to forage testing labs for toxin analysis. Even if levels appear high, diverse forage availability can reduce the amount of toxin animals ingest.
Because recent pasture stress may increase future risk, livestock owners should monitor symptoms closely and take early action to protect herd health.
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