Perennial Ryegrass

Perennial ryegrass (Lolium perenne) is a common perennial pasture grass which is often contaminated with the fungal endophyte, Neotyphodium lolii. This fungi produces toxic alkaloids, specifically lolitrem B.

Ryegrass staggers occurs variably, depending on the weather conditions. The toxicity increases during the summer and fall and may remain at high levels for 5 to 6 months. Ruminants will typically begin to demonstrate signs of ryegrass staggers 7-14 days after grazing the plant. Prolonged exposure to the toxins can cause permanent neurological damage to the animal.

Infected ruminants may appear normal when left on their own in the pasture, however when asked to move they appear incoordinated, stiff, weak, and look like they might fall over. Many ruminants with this condition are found dead due to accidental means such as falling into the water and drowning. Perennial ryegrass can also produce high levels of water-soluble carbohydrates.