Tall fescue (Lolium arundinaceum Schreb.) is a widely cultivated forage grass known for its versatility and adaptability. However, the presence of an endophytic fungus (Acremonium coenophialum) within tall fescue plants can have significant implications for animal health and performance. This article explores the effects of endophyte-infected tall fescue on livestock and horses, highlighting the associated risks and potential management strategies.
Key Facts
- Reproductive difficulties: Mares grazing on toxic endophyte-infected fescue can experience severe reproductive difficulties, including abortions, prolonged pregnancy, foaling problems, thick or retained placentas, and agalactia (little or no milk production).
- Tall fescue toxicosis: Consumption of endophyte-infected fescue can lead to a syndrome known as tall fescue toxicosis. This syndrome can cause poor animal health and performance, including symptoms such as fescue foot, fat necrosis, and summer slump.
- Ergot alkaloids: The toxic effects of endophyte-infected fescue are primarily attributed to the presence of ergot alkaloids, which are produced by the endophytic fungus. These alkaloids can disrupt normal body functions and metabolism in animals, leading to various health issues.
- Widespread use: Tall fescue is one of the most widely used forages in the United States, particularly in the livestock and equine industries. It is valued for its hardiness, nutritive qualities, and ease of cultivation. However, the presence of the endophyte and its associated alkaloids has raised concerns about animal health and performance.
Toxicity and Health Concerns
The primary concern associated with endophyte-infected tall fescue is its potential toxicity to grazing animals. The endophyte produces ergot alkaloids, which are toxic compounds that can disrupt normal body functions and metabolism. Consumption of endophyte-infected fescue can lead to a syndrome known as tall fescue toxicosis, characterized by a range of adverse effects on animal health and performance.
Effects on Cattle
In cattle, tall fescue toxicosis can manifest in several ways:
- Fescue Foot: A dry, gangrenous condition of the body extremities, particularly the tail and ears, caused by vasoconstriction and reduced blood flow.
- Bovine Fat Necrosis: Accumulation of hard fat masses in the abdominal cavity, leading to digestive and calving problems.
- Fescue Toxicity: Reduced feed intake, weight gain, and milk production; increased respiration rate; elevated body temperature; rough hair coat; increased time spent in water or shade; and reproductive issues.
Effects on Horses
Horses are particularly susceptible to the reproductive effects of endophyte-infected tall fescue. Mares grazing on toxic fescue pastures may experience:
- Abortions: Increased risk of pregnancy loss.
- Prolonged Pregnancy: Gestation periods longer than normal.
- Foaling Problems: Difficulty delivering foals, leading to foal and/or mare mortality.
- Thick or Retained Placentas: Complications during foaling.
- Agalactia: Reduced or absent milk production.
Management Strategies
To mitigate the risks associated with endophyte-infected tall fescue, several management strategies can be employed:
- Use Endophyte-Free or Novel Endophyte Varieties: Planting tall fescue varieties that are free of the toxic endophyte or contain a novel endophyte that does not produce harmful alkaloids can eliminate the risk of tall fescue toxicosis.
- Grazing Management: Implementing rotational grazing practices and avoiding overgrazing can help reduce the intake of toxic alkaloids by animals.
- Supplementary Feeding: Providing alternative feed sources, such as hay or grain, can dilute the intake of toxic alkaloids from fescue pastures.
- Fertilization: Applying nitrogen fertilizer to fescue pastures can increase forage production and reduce the concentration of toxic alkaloids.
- Herbicide Application: Using herbicides to control endophyte-infected tall fescue plants can help reduce the prevalence of the toxic endophyte in pastures.
Conclusion
Endophyte-infected tall fescue can pose significant health risks to grazing animals, particularly cattle and horses. The presence of ergot alkaloids produced by the endophyte can lead to a range of adverse effects, including reproductive issues, reduced performance, and even death. By employing appropriate management strategies, such as using endophyte-free or novel endophyte varieties, implementing rotational grazing, and providing alternative feed sources, producers can mitigate the risks associated with endophyte-infected tall fescue and ensure the health and well-being of their livestock.
FAQs
What is endophyte-infected fescue?
Endophyte-infected fescue is a type of tall fescue grass that contains a fungal endophyte (Acremonium coenophialum) that lives within the plant’s tissues. The endophyte produces ergot alkaloids, which can be toxic to grazing animals.
What are the effects of endophyte-infected fescue on animals?
Endophyte-infected fescue can cause a range of adverse effects on animal health and performance, including reduced feed intake, weight gain, and milk production; increased respiration rate; elevated body temperature; rough hair coat; increased time spent in water or shade; reproductive issues; and fescue foot (a dry, gangrenous condition of the body extremities).
How can I tell if my tall fescue is infected with endophyte?
It is not possible to visually distinguish between endophyte-infected and endophyte-free tall fescue plants. Laboratory testing is required to determine the endophyte status of tall fescue.
What management strategies can I use to reduce the risks of endophyte-infected fescue?
Several management strategies can be employed to mitigate the risks associated with endophyte-infected tall fescue, including using endophyte-free or novel endophyte varieties, implementing rotational grazing, providing alternative feed sources, applying nitrogen fertilizer to fescue pastures, and using herbicides to control endophyte-infected tall fescue plants.
What is fescue foot?
Fescue foot is a dry, gangrenous condition of the body extremities, particularly the tail and ears, caused by vasoconstriction and reduced blood flow. It is one of the most common signs of tall fescue toxicosis in cattle.
What are ergot alkaloids?
Ergot alkaloids are toxic compounds produced by the endophytic fungus in tall fescue. These alkaloids can disrupt normal body functions and metabolism in animals, leading to various health issues.
What is novel endophyte tall fescue?
Novel endophyte tall fescue is a type of tall fescue that contains a modified endophyte that does not produce harmful ergot alkaloids. This type of tall fescue provides the benefits of endophyte-infected fescue, such as improved drought tolerance and pest resistance, without the associated toxicity risks.
What is the difference between endophyte-free and novel endophyte tall fescue?
Endophyte-free tall fescue does not contain any endophyte fungus, while novel endophyte tall fescue contains a modified endophyte that does not produce harmful ergot alkaloids. Both types of tall fescue are non-toxic to grazing animals.