With the rapidly changing temperatures as we move further into the spring season, ergot poisoning becomes a greater concern in hay production. Drastic environmental conditions such as the recent devasting floods across the U.S. can also have an effect on ergotism incidence.
Ergot is a fungus that grows on the seed head of cereal grains and grasses. A cool and wet spring followed by an early and hot summer is the prime condition for the fungus to grow. A late harvest of grass hay due to heavy rains means the late cut hay can also be at risk of ergotism.
Historically, rye has been the grain with the highest incidence of ergot. However, wheat, oats, and barley are additionally affected by the fungus. According to the University of Wisconsin-Madison Extension, signs of ergot first appear as droplets of a sticky substance called honeydew on immature grain heads.
Onset of ergot infection
Honeydew contains asexual spores of the ergot fungus. Many species of insects are attracted to honeydew and can transfer the substance from infected plants to healthy plants. The spores are deposited on the plant and after two weeks, the grains become infected by dark fungal structures called sclerotia, which can look like seeds or rodent droppings.
After a two-month period, the asexual sclerotia germinate and form mushroom-like sexual spores. The sexual spores are then blown by the wind to developing grain heads, where they cause an infection. High humidity can increase honeydew production, and germination of sclerotia is highest during damp weather and drastically increases during wet periods.
Several species of the fungus Claviceps cause ergot, most commonly Claviceps purprea. The fungus causes ergotism because of the number of toxic alkaloids it contains. Sclerotia from this specie can survive in the soil as well as harvested grain.
Little can be done to treat ergot infections in hay and grain crops, as fungicide treatments are not recommended. Commercial seed cleaning equipment may be able to remove sclerotia, but if the sclerotia is broken or large in size, removal can be difficult and costly. Even after attempts to remove the sclerotia, the grain may still have a contamination level that is above the tolerance threshold.
Symptoms in livestock
Although all animals can be affected by ergot, cattle are most susceptible. A cattle ration with only 0.3 percent of sclerotia can cause gangrenous ergotism, also called fescue foot. Although horses are rarely affected, a nervous form of ergotism is more common for them.
Gangrenous effects from ergot alkaloids are a result of impaired circulation by vasoconstriction of the blood vessels, causing a loss of blood supply to the extremities. Symptoms will typically be seen from two to six weeks after ergot consumption. Signs in the early stages can include weight loss, elevated respiration rates, reduced feed intake and milk production, and reproductive issues such as abortion or dystocia.
Clinical signs of gangrenous ergotism can result in the partial or total loss of the tail and ears, as well as sloughing of the hoof tissues. In severe cases, entire hooves can be lost due to the deprivation of blood flow.
Horses typically exhibit a nervous form of ergotism, although in extreme cases, gangrenous symptoms may be observed. The first signs of nervous ergotism are dizziness or an unsteady gait. Additional signs include lameness, difficulty breathing, excessive salivation and diarrhea.
Preventative measures
If caught soon enough, livestock can recover from the poisoning. However, once gangrene has started, little can be done. Treatment requires the removal of the animals from the affected grains, pastures, or hay. Destroying the contaminated grains or hay from an affected field may also be the best course of action.
Prevention is key for ergotism treatment. Grass should be monitored regularly for signs of ergot sclerotia. Sometimes the sclerotia can be knocked off as it is being handled, so hay should also be inspected to make sure it does not contain sclerotia. Although ergot-resistant varieties of small grains are not available, avoid longer-flowering varieties as they can be more susceptible to infection.
Mowing areas adjacent to small grain fields can help prevent flowering and onset of infection. If ergot becomes a problem, deep plowing can bury sclerotia and prevent it from germinating. Do not allow animals to graze in ergot-contaminated areas and do not use the harvested material at all, including as bedding material.
With the especially high risk of ergotism due to unusually wet conditions, monitoring crops is essential to help prevent onset of ergot infection. If feed is contaminated, early recognition of the clinical signs can save livestock. — Anna Miller, WLJ correspondent
