This year’s cool, wet spring followed by the recent heat wave increases the risk of ergot poisoning in grazing cattle, warns Russ Daly, a South Dakota State University (SDSU) Extension veterinarian.

The weather has been ideal for the development of dark brown to black growths on the seed heads of grasses and grains, says Daly. These ergot bodies result from a fungus that grows well in warm weather and infects over 200 species of grasses throughout the country. Examples of species infected include wheat, barley, oats, bromegrass and wheatgrass.

All domestic animals are susceptible to the effects of ergot; however, due to their diets, ruminants are usually more commonly affected than others, Daly says.

The ergot bodies contain several toxic substances produced by the fungus, called ergot alkaloids, explains SDSU veterinary pathologist Regg Neiger.

"The effects of these toxins on animals can vary widely and cause both problems systemically overall, as well as with the extremities of the animal," says Neiger.

In cattle, a common peripheral effect of ergot poisoning is a constriction of the small blood vessels to their extremities, like the ears, tail and feet. Blood flow may be compromised, and in severe cases result in gangrene or a sloughing off of hooves and the distal parts of ears and tails.

Initially, animals may appear to be in pain and lame; that may be initially confused with other causes of lameness, such as foot rot. However, on closer examination the extremities affected animals are cool to the touch, and there is a line of demarcation between normal and non-healthy tissue. Other initial signs of ergotism are also quite non-specific: increased susceptibility to heat, reduced feed intake, rough hair, weight loss and decreased milk production. The cattle may be excitable, especially when forced to move.

Diagnosis of ergotism is usually made on the basis of clinical signs and presence of large numbers of ergot bodies on grain or grass. Chemical analysis of suspected grass, hay or grain for the ergot alkaloid toxins can be performed, if needed.

Treatment of ergotism relies on removal of the affected animals from the offending feed source and providing supportive care to manage pain, stress and secondary infections of the affected body parts.

Preventing ergotism involves removing animals from infected pasture, if possible. Mowing or pasturing grass before it flowers will prevent the formation of ergot bodies.

If you think your livestock may be affected by ergotism, contact your local veterinarian, Daly and Neiger advise.