Ergot is a fungus that lives as a parasite in the blossoms of grass. When the grass heads are nearly mature, it appears as jumbo grains protruding from the heads. Ergot grains, which are fungus bodies and not seeds, are several to many times the size of the grass seed. They are dark violet to almost black and are curved, hard, and hornlike. Ergot varies in abundance from year to year. The most common ergot endophyte around the north central Kansas area is Claviceps Purpurea.
Ergot is well known as a disease of rye. It also attacks many of the wild grasses that grow along roads, in fencerows, woods, meadows, pastures, and can often be found on wild rye, quackgrass, redtop, and brome grass.
Conditions of poisoning
Animals get ergot either in the grain fed to them or by grazing on infected grass. Obtained in either way, ergot may cause acute poisoning if a large quantity is eaten at one time. Also, because the effect of ergot is cumulative, poisoning may develop slowly if lesser quantities are eaten regularly. Experiments have shown, however, that a small amount of ergot is not injurious to dairy cattle that are amply provided with a balanced ration.
The toxic action of ergot is due to the numerous alkaloids (ergotamine, ergocristine, ergonovine, etc.) present in the sclerotia and other components–choline, ACH, histamine, sterols. Over 40 alkaloids have been identified which are derivatives of lysergic acid, some of which are inactive.
The important naturally occurring alkaloids are ergotamine and ergonovine. Of these, ergonovine is more readily absorbed. Both compounds are potent smooth muscle activators. LSD is also derived from ergot, and the smooth muscle contracting activity, although sometimes present, is not always seen. LSD causes depersonalization or hallucinations and may produce toxic psychosis.
All animals are susceptible to ergot but cattle are often most affected.
- The fungus produces toxic compounds called ergot alkaloids which are vaso-active causing severe vasoconstriction of small arteries.The extremities of cattle are most often affected causing loss of the tips of ears and tail. We have seen a lot of cattle affected in the rear legs and occasionally the front showing multiple horizontal breaks in the skin along the cannon bone.
- Depending on the level of ingestion, feet and legs can be affected as well – causing signs of lameness with potential swelling observed in the fetlocks and hock joints and, in severe cases, loss of hooves.
- Changes in blood flow can also affect thermoregulation and result in heat intolerance.
- Summary: Summer slump (failure to grow/losing weight), necrosis of the extremities (tail switch, ear tips, hooves and legs), decreased conception rates and in rare cases abortions from uterine contractions caused by the chemicals in ergot.
- Cattle will commonly develop a rough hair coat, lose weight and have extended periods of time standing in water or shade if available.
There is no one way to manage this problem in the pasture, recommendations are based off of the clients management scheme and available resources. Ergot thrives in an early warm wet season that turns into a very hot summer, but it can show up in many different situations. Mowing the grass, swathing or waiting until the seed heads fall off (wind, rain, maturity) are the most common ways of trying to decrease the amount of ergot in the pasture. If you find ergot in the pasture and the owner wants it tested for the toxicity levels he/she can walk the entire pasture in a W or X pattern and collect a trash bag full of grass evenly distributed throughout the pasture. Then take and grab a 2 gallon Ziploc bag of grass from this trash bag so you have a small sample to be sent in that represents the entire pasture. This test is about $90 and can be sent to the University of Missouri Veterinary Medical Diagnostic Laboratory.
What can mimic this? Fescue toxicosis, Acute/Chronic selenium toxicity and interdigital necrobacillosis (foot rot)