Mares grazing on tall fescue pastures infected with a toxin have increased gestation lengths, mare and foal deaths, agalactia (absent milk secretion after birth), retained placentas, premature separation of the placenta at birth, and increased placental weights and thickness. The endophytic fungus, called Acremonium coenophialum, lives on the grass and has been reported to cause all of the previously mentioned reproductive problems in mares.

Where is the infected fescue?

This endophyte is prevalent in fescue-growing regions throughout the United States. Fescue toxicosis, however, appears to have regional and seasonal preferences. Veterinarians in the northern regions of the United States report lower toxicity levels, agalactia, and dystocia. However, premature placental separations ("red-bagging") appear more frequently. On the other hand, a warm or mild winter in the northern states tends to exacerbate toxicosis conditions.

In the more southern fescue-growing regions of the country, count on a high level of fescue toxicosis in mares regardless of the severity of winter weather.

How can you tell if your fescue is infected?

There are many ways to tell if your pasture is infected.

* Have broodmare pastures evaluated for toxin levels, especially if fescue toxicosis is suspected or is prevalent in your area. Send a sample to the local extension agent to have the forage tested.

* Evaluate past records and the history of the farm. If problems such as low milk levels or weak foals increase after mild winters, or if toxicosis symptoms decrease after a hard winter, then the endophyte is probably present.

* Observe for fescue toxicosis symptoms as described above. Any of these can indicate
an endophyte problem.

Can you treat it?

If the endophyte is suspected in a broodmare pasture, remove pregnant mares 60 to 90 days before foaling. Thirty days is an absolute minimum.

If removing the mares from the pasture is not an option, studies show that domperidone, available from your veterinarian, is the most effective means of relieving fescue toxicosis symptoms. Mares on this drug show shorter gestation lengths, have live foals that are born closer to the delivery date, have more mammary development, are not agalactic and have higher prolactin and progesterone levels. This daily, oral paste is started 20 days prior to the expected foaling date if mares remain on the endophyte-infected pastures.

Some extension services recommend replacing infected fescue with endophyte-free varieties of tall fescue. They suggest destroying the infected pasture with an herbicide and replanting with newly developed endophyte-free fescue. However, this option can be costly because of the time and resource investment, and studies have shown that after 2-3 years, there is a high probability of reappearance of the toxins in the fescue.

It is up to farm and barn managers to integrate many sound management practices into the breeding program to alleviate fescue toxicosis symptoms. Please consult with your veterinarian on options to treat fescue toxicosis.

About the Author

D.L. Cross, DVM

Dr. D. L. Cross is a professor of animal sciences at Clemson University. He currently is researching nutritional toxicology while working with many different species, but he specializes in cattle and horses.

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