When walking in pastures this summer I have observed lots of dallisgrass. Dallisgrass is a perennial warm-season grass that proliferates in warm, wet summers but can also be plentiful in dry summers. Due to ideal growing conditions this summer, the increased growth has produced more seed heads and therefore the increase of possible issues.
Dallisgrass staggers is due to a toxin made by a fungus, which infects the seed head of dallisgrass. Cows eating infected seed heads become in-coordinated and may appear drunk. Removing cows from infected pastures usually results in uneventful recovery in three to five days.
A fungus, named claviceps paspali, commonly infects the flowers of dallisgrass. This infection happens most often during warm, moist summers. By September, an infected fungal mass, called an ergot body, has replaced the seed. This ergot body is light tan to orange or brown in color and round in shape. Eventually, the ergot body will become shrunken and black. These ergot bodies contain the toxic agent, which is responsible for clinical signs.
Some cattle may show a preference for grazing these seed heads. Clinical signs of dallisgrass staggers are most frequently seen in cattle but may also happen in sheep and horses. Signs may happen as early as three days after animals are introduced to an infected pasture. Hay baled from infected pastures may sometimes produce a problem. Up to half of the herd may show signs, but deaths are rare except in cases of injury associated with in-coordination in affected animals.
Clinical signs associated with dallisgrass staggers involve the animal’s nervous system. In the early stages of the disease, the only sign seen may be trembling of various muscles after exercise. As the disease progresses, muscle tremors worsen so that the animal may show continuous shaking of the limbs and nodding of the head. When forced to move, this severely affected animal may stagger, walk sideways and display a “goosestepping” gait. In-coordination can be severe enough the animal will fall down when she attempts to walk. Some animals may be found down and unable to stand. Diarrhea may be noted in some affected animals.
There is no specific treatment for dallisgrass staggers, though oral administration of activated charcoal and laxatives may hasten recovery. The affected group should immediately be moved to an uninfected pasture or the pasture can be clipped long enough to leave the grass and short enough to remove the seed heads, which fall to the ground and are not eaten. Affected animals should be moved slowly and carefully to avoid injury. Complete recovery should happen in three to five days for most animals but occasionally may require up to three weeks.
Preventing this problem is based on the use of short-term, intermittent grazing or mowing the seed heads off the plant and allowing the seeds time to work their way to the ground where they are unlikely to be grazed. Early recognition of the problem and moving cows to a safe pasture should result in elimination of signs in a few days.
For more information, contact the UT-TSU Extension Office in Wilson County at 615-444-9584. You can also find us on Facebook or visit extension.tennessee.edu/wilson. Ruth Correll, UT Extension-TSU Cooperative Extension agent in Wilson County, may be reached at 615-444-9584 or firstname.lastname@example.org.