Ryegrass can be infected with endophyte fungus. The toxins the fungus produces causes nerve and muscles disorders. Symptoms of poisoning are staggering, stiffness, swaying back and forth when standing still, muscle twitching, excessive salivation, teeth grinding and convulsions.
Ryegrass varieties that are used in lawns must not be used in pastures – these seeds are not endophyte free. Ryegrass varieties developed for pasture and hay should be labeled endophyte free.