FESCUE IS A HARDY, EASY-GROWING grass that was established in the United States in the 1940s and grows on more than 35 million acres of land. Of the pastures that grow the tall fescue, many contain plants that are infected with a fungus, Acremonium coenophialum, that is toxic to horses.
This fungus lives within the plant without altering its appearance and is transmitted only through the seed; it is not found in the soil and can’t transfer between plants. The only way to know if your pasture is infected is through laboratory analysis.
Fescue toxicity can increase the incidence of breeding-related complications, such as abortion, prolonged pregnancy, laminitis, thickened and retained placenta, and dystocia (foaling difficulties). Foals born to mares eating the infected plants often are born weak and don’t survive long postpartum. Affected mares may take longer to cycle after foaling or be difficult to get back in foal.
Since avoiding infected plants in pasture can be difficult, there are several steps you can take to avoid the complications. Regular mowing of pastures before the seeds develop can keep the level of infection down. Remove pregnant mares from infected fields 60 to 90 days before foaling. Once the infected food source has been removed from their diet, the mares generally recover and have a normal pregnancy. Mares and foals should be kept off the infected pastures until the foals are weaned because of decreased milk production.
If you have any concerns about your mare or are unsure of breeding dates, it is better to be safe and keep the mare off all infected pasture. If you have any questions or concerns, please contact your veterinarian.
column by DR. KATIE HENNESSY
BIO: Dr. Katie Hennessy graduated from the University of Illinois College of Veterinary Medicine in 2008 with a degree in large animal health and equine medicine. After completing an advanced internship and working as an Associate Veterinarian, she is currently practicing at Polk Equine, LLC. Her expertise ranges from small and exotic creatures to large animals, specializing in equine medicine.