Understanding the Rising Concerns Around Fescue Toxicosis in Livestock

By Andi Anderson

Concerns about fescue toxicosis are increasing as cases appear to be spreading farther north or becoming more widely recognized.

Farmers in southern states have dealt with this issue for many years, especially due to its severe effects on horses. However, research has also shown that fescue toxicosis can significantly impact beef cattle performance and even affect small ruminants.

Fescue toxicosis occurs when livestock consume tall fescue containing a toxin called ergovaline. This toxin is produced by an endophyte, a fungus that naturally grows inside tall fescue plants.

While harmful to animals, the fungus benefits the plant by improving drought tolerance, disease resistance and insect protection. Because of this, infected tall fescue survives harsh conditions better than many other grasses.

The symptoms of fescue toxicosis can vary widely among livestock species. Since ergovaline restricts blood flow, animals may experience lameness, loss of hooves or tails, increased body temperature, rough hair coats, low milk production, pregnancy loss or poor weight gain. Many other conditions may look similar, so proper diagnosis with the help of a veterinarian is important.

Toxin levels are usually highest in late spring and summer when seedheads develop, because seedheads contain the most ergovaline.

Later in the year, toxin concentration increases near the base of the plant. During periods of overgrazing, animals may consume more of this lower portion, increasing health risks.

Recent drought conditions may have intensified the problem. The fungus helps tall fescue survive drought, meaning infected plants can become more dominant when other grasses struggle or die.

Weeds often fill gaps left by stressed plants, and the combination of overgrazing and reduced forage diversity makes it harder to dilute toxins naturally.

Producers have several management options. Increasing forage diversity is one of the simplest approaches.

Adding red or white clover is effective and can be done through frost‑seeding in late winter. Seeding other grasses can also help, especially when using a no‑till drill. Because the endophyte is specific to tall fescue, planting other species reduces toxin intake.

Producers who want to remove infected fescue must use a multi‑step approach, as infected seeds can survive in the soil. Endophyte‑free tall fescue varieties exist but may not persist long‑term.

Novel endophyte varieties are a stronger option because they provide the plant benefits of endophytes without producing harmful toxins.

Toxin levels gradually decrease in stored hay and stockpiled forage, offering additional management opportunities. Avoiding high‑risk areas and improving pasture diversity can significantly lower exposure.

Pasture testing through forage labs is available, and Extension educators can help producers interpret results. Even when toxin levels are high, offering other forages or supplemental feed can dilute the amount animals consume.

Producers should remain alert, particularly after years of drought stress, which may contribute to higher toxin levels. Watching for early symptoms and adjusting pasture management can help protect livestock and maintain healthier grazing systems.

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