According to the Ohio State University Extension Department of Horticulture and Crop Science, tall fescue grows on an estimated 35 million acres in the United States. As a cool-season perennial grass, fescue is primarily found in Northeast region. Distributed throughout Ohio, fescue grows in a variety of growing conditions and low fertility soils. As a prime source of crude protein, fiber and minerals for foraging livestock, many Ohio pastures feature fescue or a mix of fescue with other forage grasses. However, livestock grazing on high levels of fescue often display negative symptoms referred to as fescue toxicity.
Fescue toxicity is not actually caused by the fescue itself, but by an endophytic fungus growing within the fescue planted in Ohio pastures. Living between the plant cells of the fescue, the endophytic fungus spends the winter in the lower part of the perennial. In the spring, the fungus moves upwards through the flower and seed head. The infested seed is then spread, producing infected fescue plants.
The endophytic fungus in the plant produces ergot alkaloids, which have a residual effect in livestock. Retained in the fat tissues, the alkaloids affect many different systems within the animal.
Speculation suggests that the first fescue planted in the United States contained infected seeds, according to the Ohio State University Extension Department of Horticulture and Crop Science. Samples of Ohio tall fescue indicate that approximately 56 percent of plants are infected.
Endophyte-free cultivars were introduced during the 1980s. However, producers soon discovered that endophyte-free fescues lacked the ability to recover from drought stress.
Researchers are currently working with introduced endophytes in order to produce cultivars of fescue infected with beneficial endophytes. The beneficial endophytes produce little to no ergot alkaloids, reducing the toxicity to livestock.
Tall fescue toxicity presents itself in numerous ways in both cattle and horses. Fescue foot in cattle occurs when blood flow is restricted to the extremities, resulting in hoof loss during cold weather. The ears and tails may also be affected by the reduced blood flow. Cattle suffering from fescue toxicity in Ohio often fail to lose their winter hair, suffer a reduced rate of gain or loss of weight, exhibit increased body temperatures and may pant or salivate excessively.
Both horses and cattle on infested fescue pastures experience increased miscarriage and stillborn births. Birth weights are lower and milk production is reduced. According to the Plant Management Network, birthing difficulty and placenta problems increase greatly when infested tall fescue is consumed by the horse during late gestation.
Testing for Fescue Endophytes
As of 2010, Ohio State University Extension does not test for tall fescue endophytes. The Department of Horticulture and Crop Science recommends sending samples from 30 different tillers located randomly within each field to the Fescue Diagnostic Center in Auburn University, Alabama.
Several management options exist for Ohio fescue pastures in order to reduce fescue toxicity in livestock. Once tested positive for the endophyte, the total pasture can be replaced by using a herbicide to kill all fescue, then replanting with a new forage crop. Most producers spray and replant small areas at a time to keep pasture available for livestock.
The rotation of cattle off of fescue pastures during the late spring throughout hot summer months may help limit the amount of ingested toxins. In addition, mowing the fescue before it reaches a seed-head stage also reduces the amount of toxins available for ingestion.
Interseeding infected pastures with legumes and other forage grasses helps to reduce the amount of toxins ingested by livestock. Supplementation of hay and other feed sources may help in toxin reduction as well. In order to make sure the animals are receiving the proper balance of non-toxic to toxic feeds, a veterinarian can perform blood tests.