Abstract
From 1997 to 1999, we experienced 29 cases of disorders in cattle and horses that had been fed ryegrass straw imported from the USA. These animals showed symptoms resem-bling ryegrass staggers and the clinical signs disappeared after removal of the straw. To clarify the cause of these cases, we examined the suspected straw for the presence of endophytic fungi and toxins. Endophytic hyphae were detected in the seeds of all straw samples that were responsible for the clinical cases. Lolitrem B concentrations in the straw ranged between 972 and 3740 ppb. Ergovaline concentrations were between 355 and 1300 ppb. It is known that N. lolii-infected perennial ryegrass contains both lolitrem B and ergovaline. Our result was comparable with the observations of previous reports. Turner et al. (1995) proposed the threshold levels of lolitrem B for toxicity as 1800-2000 ppb in the total diet. Even though the concentrations of lolitrem B were lower than this proposed threshold in almost all clinical cases, we diagnosed the episodes as ryegrass staggers from the clinical signs and other epidemiological findings. Namely, neurologic disorders were diminished by deprivation of the suspected straw. Vitamin B1, calcium or magnesium deficiency, white muscle disease and nitrate poisoning were ruled out by the clinical exami-nations. Furthermore, experimental feeding of the straw produced typical neurologic signs.
