What is a potential health issue caused by cattle grazing on older tall fescue pastures?

Cattle grazing on older tall fescue pastures can experience health issues primarily due to fescue toxicosis caused by an endophyte fungus, specifically a type of fungus that lives symbiotically in the grass. This fungus produces toxic alkaloids, such as ergovaline, which can adversely affect cattle. Symptoms of fescue toxicosis may include reduced weight gain, poor reproductive performance, and elevated body temperature, particularly in hot weather. The presence of the endophyte fungus is more common in older fescue pastures, making it a significant concern for cattle producers managing pasture health.

While prussic acid accumulation, nitrate poisoning, and ergot sclerotia contamination can also pose risks to cattle under certain conditions, they are generally associated with different plant species or specific growth conditions rather than being a chronic issue linked to older tall fescue pastures. Understanding fescue toxicosis is essential for cattle management on these types of pastures.