Dallisgrass Poisoning Can Occur in Late Summer
Dallisgrass poisoning (also known as Dallisgrass staggers) occurs several days after cattle ingest a significant amount of dallisgrass seedheads infected with an "ergot-like" fungus called Claviceps paspali. The seedheads typically are infected with the fungus in the fall, as the seedheads age. Rather than flat looking seeds on the heads, the infected heads have gray to black swellings that have a sticky sap material on them. Some observers say it looks like little popcorn (see photos of normal and infected seedheads). Usually not all the herd is affected, and it appears that it occurs when some animals develop a preference for the tips of the seedhead.
The infected seedheads contain three primary toxins, paspalinine, and paspalitrem A and B, which are tremorgenic alkaloids. The affected animals show neurological symptoms, including trembling of the major muscles and the head, jerky uncoordinated movements, and they also are spooky and sometimes aggressive. The animals will startle and run, and often will fall in unusual positions. In bad cases the animals will go down, and may stay down for several days. Convulsions and death can occur in extreme cases. The symptoms are somewhat like grass tetany, and this is often misdiagnosed, but they don't show the sudden death characteristic of grass tetany, and don't immediately respond to treatment for grass tetany.
There is no treatment for the malady, except to get the cattle off the affected grass, and provide them with high quality forage. If possible they should be put in a field with no ponds, steep slopes, etc. as they commonly stumble around and end up injuring or drowning themselves. Usually cattle can completely recover from the poisoning.
In late summer we often have reports of dallisgrass poisoning, and it seems to be getting more common now because there is more dallisgrass in pastures in North Carolina. Toxicity usually is reported on farms with rank dallisgrass seedheads and the fungus present. In many cases producers had stayed off the pastures hoping to let the grass get a little more growth on it, and as a result the seedheads got old. In other cases, there are only a few cattle in large pastures, so the Dallisgrass grew faster than the cattle could consume it. Rarely do we get a report of a case were there deaths of the affected cattle. It also seems that in many cases the younger cows are affected, which suggests that cows may learn to avoid eating too much of the seedheads after getting too much (cattle are known to learn to avoid poisonous plants in this way).
Dallisgrass is becoming a more important part of many pastures in the piedmont and coastal plain. It is a very good quality warm season perennial, and provides great benefits to pasture systems, but the one drawback is the potential for Dallisgrass staggers. By rotational grazing the grass after seedheads emerge but before the fungus grows on them the problem can be avoided, because cattle will readily eat the immature seedheads unlike some other grasses we are used to. If the seedheads do become infected, clipping them off at about 12" before grazing should
help prevent the problem. Hay with high amounts of seedhead can also be a problem, so feeding Dallisgrass hay along with other hay is advised, especially if infected seedheads are present.
For more information concerning dallisgrass poisoning contact Matt_Poore@ncsu.edu, your extension agent or your veterinarian.
last modified by forageweb, September 2000