Tall fescue is a ubiquitous forage grass that became popular because of its drought tolerance, hardiness, and good forage performance. However, in the 1970s scientists discovered a high percentage of tall fescue harbors an endophyte that produces a toxic alkaloid with the ability to cause disorders in ruminants and horses that consume large amounts.

Garry Lacefield, PhD, UK plant and soil sciences extension forage specialist refers to the Mid-South region, which includes Kentucky, as the "tall fescue belt" due to tall fescue quantity in the area.

Tall fescue covers an estimated 35 million acres in the United States, including pastures, high-traffic foot paths, golf courses, and backyards. A majority is endophyte-infected (EI). An endophyte is a fungus that lives symbiotically within the host plant and is not visible to the eye. The endophyte produces toxic alkaloids that, when eaten, cause different disorders including tall fescue toxicosis.

Tall fescue toxicosis causes problems in broodmares during the last third of gestation. Thus, understanding and managing tall fescue is important, particularly as the foaling season approaches.

According to "Understanding Entophyte-Infected Tall Fescue and Its Effect on Broodmares," tall fescue toxicity in broodmares can manifest as follows:

  • Poor animal performance (rough coat, low grade fever)
  • Longer pregnancy (as long as 13-14 months)
  • Agalactia (poor milk let-down)
  • Dystocia (difficulty foaling)
  • Thickened placenta ("red bag" foal