Horses Grazing Fescue Require Sound Management
By Donald Stotts

STILLWATER - The ability to use tall fescue as pasture for horses is a helpful aid to many owners' pocketbooks, though it is a practice that takes sound management.

Much of Oklahoma's fescue is infected with an endophyte that can cause health problems in horses. Unfortunately, ridding pastures of fescue is difficult, time-consuming and expensive.

"Unless the fescue in your pasture has been planted with 'endophyte-free seed' the past few years, and was entirely devoid of fescue before then, you can count on the fescue to be endophyte infected," said Dave Freeman, Oklahoma State University Cooperative Extension equine specialist.

Freeman said the amount of infected fescue in pastures with several types of forage may be larger now compared to a few years ago. "Horses typically prefer to eat other forages," he said. "This preferential grazing allows the fescue to propogate more and the grazed forages to propogate less."

Tall fescue is a cool-season, perennial bunchgrass that grows best when the average temperature is greater than 45 degrees Fahrenheit but less than 85 degrees Fahrenheit, making it ideal for the Sooner State.

Fescue typically has a split growing season in Oklahoma. It generally begins growth in September, becomes semi-dormant during mid-winter, then begins to grow again in late February before becoming dormant again during the mid-summer months.

Fescue-related problems in equines center on the broodmare, not growing animals as seen in cattle.

"If growing horses have problems, they probably are related to decreased level of intake, which causes lower energy intakes," Freeman said. "If growing horses on fescue are exhibiting poor growth, producers should supplement fescue intake with grain or hays to increase energy intake."

Difficulties with broodmares are more complicated. In cattle, problems associated with fescue consumption include decreased weight gains, increased body temperature and necrosis (death) of tissue in feet, tail and ears. Pregnant mares do not exhibit increases in body temperature or symptoms related to necrosis of tissue.

"Fescue-related problems with mares include prolonged gestation lengths, increased levels of dystocia (foaling problems) and a reduction or complete lack of milk production," Freeman said. "Lack of milk production seems to be the most consistently observed fescue-related problem."

All three symptoms have been shown to occur in broodmares when those animal are consuming mixed diets of fescue and other hays or grain, so diluting out the effect of fescue does not appear to be a solution.

"Solving the problem involves removing the source of fescue well before foaling or administering drug therapy to the mare to inhibit or correct problems," Freeman said.

General recommendations call for the removal of mares from fescue 30 to 60 days before foaling. This management tool significantly reduces problems as long as mares are removed from all sources of infected fescue, including hays.

"This means complete removal, not just a reduction of intake by feeding grain or mixing pastures with other forages," Freeman said. "Several research trials and evidence on many horse farms indicate problems may still occur in mares not removed totally from fescue."

Recently, some veterinarians have been administering domperidone, a product in the final stages of Food and Drug Administration testing. Domperidone is administered as a daily paste at least 15 days prior to expected foaling and up to foaling if fescue toxicosis is indicated. The paste is also given to mares after foaling if the horses experience problems with milk production. "

As with any drug treatment, horse owners need to consult with their veterinarians about use and expected outcomes," Freeman said.

courtesy of Oklahoma State University

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Updated: October 2005.