Tall Fescue: Potential Problem for Pregnant Broodmares

Tall fescue is a variety of coolseason grass that is found throughout Pennsylvania and the United States. It is well adapted to lowpH soils is drought resistant and can tolerate high stocking densities. Due to these traits tall fescue is highly sought after as a pasture grass. There can be however a downside to tall fescue particularly for pregnant broodmares.
Certain varieties of tall fescue are infected with the fungus Neotyphodium coenophialum formerly known as Acremonium coenophialum. The fungus is advantageous to tall fescue in that the fungus provides protection against certain insects and drought and heat. The fungus produces ergot alkaloids and it is these alkaloids particularly ergovaline that can cause harmful physiological effects in pregnant broodmares. Tall fescue known to have Neotyphodium coenophialum is known as endophyteinfected tall fescue. The amount of ergot alkaloids on a given pasture will vary depending on the time of year the amount of fertilizer present and simply plant variation.

Pregnant broodmares that consume endophyteinfected tall fescue are at risk for developing fescue toxicosis. The symptoms in mares of fescue toxicosis include prolonged gestation abortions stillbirths thickened placentas low conception rates weak foals increased risk of newborn foal death dystocia and lowno milk production known as agalactia. You cant tell just by looking at the tall fescue if it is infected the grass must be tested.

Broodmares in late pregnancy are the only horses that are known to suffer ill effects from grazing endophyteinfected tall fescue. Nonbreeding stock have not been shown to date to suffer adversely from grazing endophyteinfected tall fescue. Research has also shown no adverse effects on stallions and their reproductive function when they graze endophyteinfected tall fescue.

So what can be done to help our pregnant broodmares? It is recommended that if your pasture does have endophyteinfected tall fescue then you should remove
pregnant broodmares from the pasture 6090 days prior to foaling. Another option is to talk with your veterinarian about treating your mare with domperidone which can help relieve most fescue toxicosis symptoms.
If you have enough acreage and can devote the time and money then renovating your pastures to remove the endophyteinfected tall fescue is another management option. You can remove the tall fescue with an herbicide and choose other coolseason grasses to plant or you could plant endophytefree tall fescue. Again this process can be costly and take several years so it might not be the best solution for everyone.