Tall Fescue: Potential Problem for Pregnant Broodmares

Pregnancy and foaling can be an exciting yet challenging time for horse owners and breeders. While many factors contribute to a successful pregnancy and healthy foal, one potential problem that often goes unnoticed is tall fescue grass. Tall fescue, a common pasture grass, can pose severe risks to pregnant broodmares if infected with a particular fungus. In this article, we will explore the dangers of tall fescue toxicity, its symptoms, and preventive measures that can be taken to ensure the well-being of pregnant mares.

Understanding Tall Fescue Toxicity

Tall fescue (Festuca arundinacea) is a perennial grass widely used in pastures and hay production due to its resilience and ability to withstand various environmental conditions. However, not all tall fescue is created equal. A specific type of fungus known as “endophyte” often infects tall fescue, leading to what is commonly called “fescue toxicosis.”

The endophyte, a symbiotic organism, lives inside the grass and produces alkaloids that can be toxic to animals, including horses. The most notorious alkaloid produced by the endophyte is ergotamine, which can lead to various health issues, especially in pregnant broodmares.

Risks for Pregnant Mares

Tall fescue toxicity poses significant risks for pregnant mares throughout their gestation period. The presence of ergovaline can interfere with the mare’s hormonal balance, leading to a condition called “fescue-induced prolonged gestation.” This condition can result in prolonged pregnancies, delayed labor, and difficult or life-threatening deliveries.

In addition to prolonged gestation, tall fescue toxicity can lead to other complications, such as weak or nonviable foals, reduced milk production, and poor overall reproductive performance. The severity of these risks can vary depending on the concentration of ergovaline in the grass and the duration of exposure.

Recognizing Symptoms

Identifying the symptoms of tall fescue toxicity in pregnant broodmares is crucial for prompt intervention and management. While some mares may show no apparent signs, others may exhibit the following symptoms:

  • Delayed or prolonged gestation
  • Reduced appetite
  • Excessive sweating
  • Loss of body condition
  • Agalactia (failure to produce milk)
  • Enlarged udder
  • Reluctance to move or lay down
  • Increased heart rate and respiratory rate

It is important to note that these symptoms can also be associated with other health issues, so consulting a veterinarian for an accurate diagnosis is crucial.

Prevention and Management

Preventing tall fescue toxicity in pregnant broodmares begins with careful pasture management. Here are some preventive measures that can be taken to minimize the risks:

  1. Test the pasture: Conduct regular testing for the presence of endophyte-infected tall fescue. This will enable horse owners to identify and address any issues promptly.
  2. Remove infected grass: If the pasture tests positive for endophyte infection, consider removing or renovating the affected areas. Replacing tall fescue with non-toxic varieties can significantly reduce the risks.
  3. Limit exposure: If obliterating infected grass is impossible, limit the mare’s exposure to the pasture during critical gestation periods. This can be achieved through temporary confinement or providing alternative forage sources.
  4. Supplement with fescue-free feed: Providing pregnant mares with high-quality fescue-free hay or feed can help mitigate the risks of tall fescue toxicity.
  5. Work with a veterinarian: Regular veterinary care and monitoring are essential to ensure the well-being of pregnant broodmares. Discussing a customized management plan with a veterinarian can help address individual mare needs and reduce potential risks.

By implementing these preventive measures, horse owners and breeders can significantly reduce the chances of tall fescue toxicity and its associated complications.


Tall fescue toxicity can be a potential problem for pregnant broodmares. The presence of endophyte-infected tall fescue and its alkaloid ergovaline can lead to various complications, including prolonged gestation and poor reproductive performance. Recognizing the symptoms and implementing preventive measures are crucial for ensuring the well-being of pregnant mares and the successful delivery of healthy foals. Through careful pasture management, regular veterinary care, and supplementation with fescue-free feeds, horse owners and breeders can minimize the risks associated with tall fescue toxicity and ensure a smooth and healthy pregnancy for their broodmares.


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