What Is Ergot?
Ergot is a fungus that is found on the seed heads of cereal grains and grasses, such as rye, triticale, wheat, barley and occasionally oats. Cool, wet weather followed by hotter temperatures are ideal for ergot fungus growth, as is delayed harvesting of late cut hay after periods of rainfall.
Ergot can be identified by looking at the seed heads for dark brown, purple or black fungal bodies (sclerotia) that are usually larger than the seeds. These sclerotia can fall to the ground over winter. There is no practical way to eliminate the fungus from the pastures and outbreaks will depend on the climate.
The fungus produces toxins called ergot alkaloids. The type and quantity of toxin depends on the species of fungus, the type of plant and the environmental conditions. This means that the clinical signs and severity of the poisoning will vary from farm to farm.
Signs of Ergot Poisoning
Ergot causes constriction of small arteries, preventing thermoregulation. Affected cattle may stand in water or shade to try and cool down. This can then progress into gangrene of the extremities – feet, tails or ears.
Cattle may go lame and a swelling of the coronary band can be observed, after which the whole hoof may slough off.
Nervous signs have also been reported due to constriction of blood vessels in the brain, causing hyperexcitability and tremors.
How Can Ergot Poisoning Be Treated?
There is no antidote, so treatment involves removing the animals from the source of the ergot and alleviating the symptoms. If found early enough and before severe clinical signs develop, animals can recover, but once gangrene has started, there is little treatment. It’s best to avoid consumption of ergot in the first place – looking for sclerotia and discarding contaminated feed is important.