Mares at risk for tall fescue toxicosis in Kentucky

By Blake Jackson

Kentucky's late summer drought, followed by mild/late fall weather and recent rains, could put mares at risk for tall fescue toxicosis, according to researchers at the University of Kentucky Martin-Gatton College of Agriculture, Food and Environment.

Tall fescue toxicosis is a condition that can occur in horses that graze on tall fescue pastures that are infected with a fungus called an endophyte. The endophyte produces a toxin called ergovaline, which can cause several problems in pregnant mares, including:

• Poor or absent milk production
• Poor udder development
• Prolonged gestation
• Thickened, retained placenta
• "Red bag" deliveries
• Potentially fatal dystocia/foaling trauma

To avoid tall fescue toxicosis, horse farm owners and managers should take the following precautions:

• Remove mares from tall fescue pastures 60-90 days before their due date.
• Feed mares high-quality hay, such as alfalfa or alfalfa mixed hay.
• Discuss managing high-risk mares and using domperidone with a veterinarian.

Once temperatures drop into the high teens, ergovaline levels typically drop for the remainder of the winter.

Here are some additional resources for horse farm owners and managers:

• The University of Kentucky Veterinary Diagnostic Laboratory (VDL) can test pasture samples for ergovaline.
• Local county extension agents can assist with sampling and results interpretation.
• The Alliance for Grassland Renewal has information about tall fescue toxicosis, including mitigation strategies and new novel endophyte tall fescue varieties with no ergovaline.
• The University of Kentucky Equines and Endophytes Workshop will be held on January 31 in Lexington.

By taking these precautions, horse farm owners and managers can help to protect their mares from tall fescue toxicosis.

Photo Credit: university-of-kentucky